# Replacing Old Filter Caps...And Why You Should



## Wilder Amplification

There seems to be a plethora of guys who own vintage amps, yet are still running the original 20+ year old filter caps in them. Some of them even wear it as a badge of honor with statements such as "I've got a 76 JMP (name your model here) with the original filter caps and it's still runnin' great!"...all part of the "If it ain't broke don't fix it" mentality.

First off..."If it ain't broke don't fix it" is just bogus logic. The trick with these amps is to KEEP THEM FROM BREAKING in the first place. This involves preventive maintenance such as normal valve replace/rebias, replacing old worn out valve sockets, cleaning of pots/jacks/switches, and...yep, you guessed it! Replacing those old worn out/dried up filter caps!

Of course I'm sure you've all heard some wannabe tech tell you "Oh techs just tell you to replace those because they wanna sell more parts". Anyone saying this is obviously inexperienced with working on amps and getting any sort of tech services from them should be avoided at all costs.

As we all know, these amps aren't cheap, nor are the most critical part of them...the transformers. Anything you can do to prolong the life of a transformer and prevent it from becoming a "sacrificial lamb" of any failed component is a worthwhile investment...and here's why.

Inside of the filter caps in a Marshall you have 3 layers of foil, all separated from each other with a dielectric wax/oil/paste coated paper. The middle layer is double the size of the other two foil layers and is your "common negative" foil plate, while the other two foil layers are your two positive foil plates. These foil/dielectric paste coated paper layers are rolled up into a cylindrical shape and installed in a metal can and form two capacitors that share a common negative.

Over time as the cap ages, that dielectric paste breaks down and dries up, and essentially breaks apart and becomes nothing but powder.

Shown below are some pictures of original filter caps that were recently removed from an '83 JCM800 2204. This is to illustrate what happens to a filter cap as it ages -






This one is that same filter cap shown alongside a JJ filter cap of the same rating that's only 6 years old with very little time on it -






As you can see, on the old cap the dielectric paste has broken down and dried up into a powder form. No way in hell does this filter cap have any more serviceable life left in it.

Now...what can this do to your amp?

Take a look at the two schematics shown below -











The top schematic is the typical JCM800 50 watt power supply while the bottom schematic is the typical 6 filter cap version of the JCM800 100 watt power supply. If you look closely, the HT fuse is DOWNSTREAM of that very first filter cap, which we'll call the "reservoir cap". This cap sustains a high load as the output valves draw lots of current from it as well as the rest of the amp so this particular filter cap sustains the highest load out of all of the filter caps in the amp. The power transformer acts as the "alternator" which continuously recharges the cap for as long as the power transformer is on.

If that cap were to short, the ONLY fuse protection it has is from the mains fuse since that cap is upstream of the HT fuse. This means that the power transformer has to sustain a high current load for the length of time it takes to blow the mains fuse. In a perfect world, this would only last a second or two as it would only take that long to pop the mains fuse. However, nothing is perfect and as such fuses are not a 100% fail safe device. Sometimes they don't blow right away. In that scenario, you can pretty much kiss your power transformer goodbye.

Now this isn't to say that "if you short a reservoir cap it's 100% guaranteed to blow your PT". Nothing is absolute, sometimes you get lucky, yada yada yada. But the risk factor of such is GREATLY increased by choosing to run those old dried up original filter caps.

So...cost of replacing filter caps? Well if your amp has 6 filter cap cans you're lookin' at about $80 + labor to replace them. However, consider this...say you have that "If it ain't broke don't fix it" mentality and decide to just up and let them blow and as a result they take out the PT. Guess what? Now you're out the cost of filter caps + cost of a new PT + labor to replace all of the above. Which would you rather do?

So if your amp is over 10-15 years old and has never had a cap job, I HIGHLY recommend getting it to a tech for one for some extra insurance. And the next time you hear someone say "I've been running the original filter caps for over 20+ years and I've had no problems" or "They're just telling you that to sell you more parts", you can now say to them with confidence "Dude, I've seen the pics of what those caps look like after 20+ years and am full and aware of what else they can take out should they happen to blow...I'm getting mine replaced!".


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## MartyStrat54

I bought two vintage amps and both sellers stated how great the amps sounded. When I sent the amps to Jon, I did not hesitate to order cap jobs for both amps. 

How foolish would it have been to spend money getting an amp modded and not change 27 year old original caps? Do you think after the mods were done the amp would have that incredible tight bottom end? Hell no.

And the thing about caps is that they react differently under various levels of power. Maybe an amp with 20 year old caps is okay since it doesn't get run past two on the volume. However, take that amp and play out with it and you have a time bomb on your hands.

I want the peace of mind knowing that both of my vintage amps have new caps.

Listen, owning a tube amp comes with responsibilities. Some guys blow off these responsibilities. Some can't even afford tubes when the tubes are bad and they continue to play their amp. I've said this before. If you cannot be committed to the responsibilities of owning a tube amp, then maybe you should go a different route.

I don't think anyone bragging that they have 25 year old filter caps is going to post up saying, "OMG, my power transformer just fried." No, we won't see that one, it won't be made public.

Morale of the story. To keep that tight bottom end and clarity, take the time to spend some money on a cap job. Your transformers will thank you.


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## TPR

I think there's also a misunderstanding about what constitutes a mod on an amp, so people avoid changing ANYTHING because they think it will devalue the amp for resale. Hopefully the clear explanations above will make people realize that old worn out caps don't hold any value, not to mention a toasted amp.


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## MartyStrat54

Jon and I discussed this and we decided that if an amp was bought strictly for a collectors piece and was never going to be powered up, then all the original components could remain.

But you're right, what good are old, worn out filter caps?


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## MM54

Yeah, my 900 (From 1990, so it's 20 years old) has 'new' JJ filter caps (in fact, all the electrolytic caps have been replaced), and being as paranoid as I am about stuff like that, I've considered replacing them since I don't know if they're 10 years old or if the guy put them in a week before I bought the amp.

Neglect is the cause of so much unnecessary technological destruction


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## Buggs.Crosby

so that's why my brain is failing after 30 years of use...oh you meant my amp head
Jon....just for the sake of the "all original" argument...is it possible to repack them? or have you ever heard of anyone trying to do it?


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## Wilder Amplification

Buggs.Crosby said:


> so that's why my brain is failing after 30 years of use...oh you meant my amp head
> Jon....just for the sake of the "all original" argument...is it possible to repack them? or have you ever heard of anyone trying to do it?



Never heard of anyone trying to do it on top of the fact that you pretty much have to damage the case to even get it open. On top of that, they would have to be unsoldered and the hardcore collectors don't consider anything "all original" unless the solder joints themselves have only been touched by the soldering irons that originally manufactured the amp, so even if it were possible it would be a moot point.


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## Lane Sparber

The misinformation on this is as pervasive as it is astounding. I was just on the phone with a tech at Mesa-Boogie last week to get a schematic for an amp I was repairing for a show. When I mentioned re-capping the amp, he told me that these caps RARELY fail and that they see original 70s Mesas with the original caps, which they NEVER replace unless they have failed outright or the customer specifically requests it. I was gob-smacked. It was amazing...and this is a PRO shop!!! Thanks again, Jon, for spreading the good word! 

-Lane


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## Wilder Amplification

Lane Sparber said:


> The misinformation on this is as pervasive as it is astounding. I was just on the phone with a tech at Mesa-Boogie last week to get a schematic for an amp I was repairing for a show. When I mentioned re-capping the amp, he told me that these caps RARELY fail and that they see original 70s Mesas with the original caps, which they NEVER replace unless they have failed outright or the customer specifically requests it. I was gob-smacked. It was amazing...and this is a PRO shop!!! Thanks again, Jon, for spreading the good word!
> 
> -Lane



The interesting thing on that is how they brag and boast that the caps RARELY fail and how original 70s Mesas are still running original caps...as if to state that this will happen in all cases on all amps. Well...

Last time I checked you can't prove a negative. Just because it HASN'T happened on certain amps doesn't mean it WON'T happen on others or on those very same amps for that matter.

Just like how the "Tone Lizard" claims that having to double the load on a 100 watt amp with two power valves removed is 99% untrue...yet it's the doubling of the load that 1/2's the current and as such the power in the first place! With 1/2 the load current you only need 1/2 the valves. Not doubling the load will make the two remaining valves try to pass double the load current without the assistance of the others which will lead to over dissipation. People who preach a lot of this shit make it clearly evident to me via their preachings that they have absolutely no clue as to what's really going on in an amplifier circuit.

Another one I found interesting is how Tone Lizard related the "transconductance" to power output in a way that makes one think that power output is all about transconductance without stopping to take into account B+ voltage against a load.

The misinfo runs rampant...'tis our job to see to it that this place blows it all out of the water with rock solid corroborated fact.


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## Lane Sparber

To that end, Jon...I would also like to discuss the scourge of the "N.O.S. Cap Seller." I have seen this happen personally. I get a line such as "well I looked on evilbay and there is this guy who has L.C.R. caps from 1985 and they have NEVER BEEN USED!!" The fallacy here, as most techs worth their salt know, is that those caps are worthless...and worse yet...just as dangerous as if they'd been used since they were made. Lack of use does NOT stop the aging and drying out process. I wanna put a hurt on those sellers...badly!

-Lane


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## MM54

Is there any downside to NOS non-electrolytic caps? They don't dry out or anything, so all logic points to old poly and ceramic caps being as good and new, assuming they don't leak, etc.


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## Wilder Amplification

Lane Sparber said:


> Lack of use does NOT stop the aging and drying out process.



No it does not. Just to clarify, these caps ARE NOT vacuum sealed, which means they're not fully shielded from the elements. This is corroborated by the fact that there was no "inrush of air" kinda sound made upon me opening up the two caps pictured above.

Furthermore, you have no way of knowing with 100% certainty that those age old caps are any good whatsoever without either opening up the can or putting it through some sort of voltage testing and testing on a scope as to the internal conditions of the cap, how/where they were stored all those years, etc etc. And even after testing I'd STILL be apprehensive about using caps that old. It's just simply not worth risking transformers for when there is a PLENTIFUL supply of current production versions of these caps available that are just as reliable as the originals were when they were new.


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## Lane Sparber

Matt- other types are usually fine. I will frequently replace ALL electrolytic caps on a client's 10+ year old amp, but I tend to leave the others alone unless they are leaky or have failed outright. Non-electrolytic caps tend to age MUCH better, as there is no electrolytic paste to dry up and evaporate. 

-Lane


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## charveldan

Kewl thread Wilder, i get one of my 78' JMP 2203's back from the bench tommorow with fresh filter caps & bias filters, that last Marshall i had done had quite a bit more mojo to it, i'm hopeing the same things goes tommorow.


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## MartyStrat54

Lane Sparber said:


> To that end, Jon...I would also like to discuss the scourge of the "N.O.S. Cap Seller." I have seen this happen personally. I get a line such as "well I looked on evilbay and there is this guy who has L.C.R. caps from 1985 and they have NEVER BEEN USED!!" The fallacy here, as most techs worth their salt know, is that those caps are worthless...and worse yet...just as dangerous as if they'd been used since they were made. Lack of use does NOT stop the aging and drying out process. I wanna put a hurt on those sellers...badly!
> 
> -Lane



Exactly...this is like someone trying to sell 8 week old "unused" banana's. No, they've never been used, but they are a nasty mess.

These guys that sell this stuff ought to have their head caved in.


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## TPR

MartyStrat54 said:


> Jon and I discussed this and we decided that if an amp was bought strictly for a collectors piece and was never going to be powered up, then all the original components could remain.



You know, on the one hand it's nice to know that showpiece Marshalls are being preserved since old hardware is always running full tilt toward extinction, but part of me feels like, "Ack, it's meant to make sound. Put some new caps in that thang and let it ROAR!"


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## Buggs.Crosby

TPR said:


> You know, on the one hand it's nice to know that showpiece Marshalls are being preserved since old hardware is always running full tilt toward extinction, but part of me feels like, "Ack, it's meant to make sound. Put some new caps in that thang and let it ROAR!"



i could be rich and pay a million for the 1st Marshall prototype ever made....if i could not play it then i wasted my money.....if i lost a half million and was rewarded with great tone i would do it.....same with a 55-56 Paul or Strat
if i cant play it then it ain't worth shit


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## MartyStrat54

Do you think Ken Bran replaced the filter caps in his Marshall #2 amp that he had for sale on EBAY? That would have been funny. "It's all original." "Really? I don't want it then." "For $500,000 you should throw in a cap job."


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## Buggs.Crosby

thats my point...i would devalue it in a heartbeat to be able to play it
it would be like having a 68 superbee and not pinning the gas pedal for at least a 10 minute full throttle run to see if it was worth my money


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## Lane Sparber

Buggs.Crosby said:


> thats my point...i would devalue it in a heartbeat to be able to play it
> it would be like having a 68 superbee and not pinning the gas pedal for at least a 10 minute full throttle run to see if it was worth my money



+1000

Also, I ALWAYS return ALL parts and components I take out of an amp to the client - so it can be "returned to stock" later (should they wish to do so) and they thus retain the "vintage" parts. I warn them about the old filter caps, though. Extensively.

-Lane


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## Joey Voltage

MartyStrat54 said:


> Do you think Ken Bran replaced the filter caps in his Marshall #2 amp that he had for sale on EBAY? That would have been funny. "It's all original." "Really? I don't want it then." "For $500,000 you should throw in a cap job."



That amp wont sell for that, Never! Basically Ken is now willing to sell, and paying the 5$ to ebay to advertise that fact, the price is so high because he doesn't intend to sell it on ebay. I bet you phone calls will be made, and that amp will be sold privately at a much, much lower price.


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## Joey Voltage

Lane Sparber said:


> Matt- other types are usually fine. I will frequently replace ALL electrolytic caps on a client's 10+ year old amp, but I tend to leave the others alone unless they are leaky or have failed outright. Non-electrolytic caps tend to age MUCH better, as there is no electrolytic paste to dry up and evaporate.
> 
> -Lane



If they stopped making polarized electrolytics even, (which is entirely possible, and is done) that would be a step in the right direction. I'm with you on the 10 year plan depending on what the amp has in it already (any general purpose elko I would change... I would consider JJ, F&T, LCR Can replacements very niche general purpose). Most newer elko caps on the market have very long life expectancy, and better ESR/ESL specs, and you can find some that will last 20+ years without any degradation.

Poly's on the other hand can last longer than than the builders life. A new fad is to use Motor run caps. Again will seldom need replacement for this purpose.


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## Joey Voltage

Now Jon. The only thing I'm going to say about the initial post is this: The PT is pretty hard to kill in a typical amp, and while it can be possible to harm it with a cap shorting due to age, it isn't the most likely of scenarios for PT destruction, and would be even harder in the second illustration which uses a series parallel connection. It would be easier to kill a PT due to heater short. 

Before the scenario of a dried up cap causing a short would take place, the amp would most likely sound, and feel like absolute crap!, and would be noisy enough to warrant servicing anyway, at which time the caps should be changed. and while I'm all on board, and gung ho about replacing elko's, I'm also not so quick as to jump to conclusions about PT failures. If you are so worried about any possible PT failures, fuse every goddamned tap like Peavey does, especially the heater supply, and call it an extra special mod


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## MartyStrat54

Are you saying that you don't see any harm in playing an amp with 28 year old filter caps? That if the amp sounds "okay" it is safe to play with old filter caps? With the volume cranked above 6? That if the filter cap shorts out "it probably won't damage anything?"

I respect my gear more than that. I didn't hesitate to get cap jobs. I'm one of those guys who actually believes in preventive maintenance. I really don't care if the damage could be slight or horrible. The bottom line is filter caps are supposed to be changed out approximately every ten years. I don't think I am going to get a nice tight tone at volume out of my amp with crappy filter caps.

Just my opinion.


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## Joey Voltage

MartyStrat54 said:


> Are you saying that you don't see any harm in playing an amp with 28 year old filter caps?



Obviously not Marty, check what I wrote above:



Joey Voltage said:


> If they stopped making polarized electrolytics even, (which is entirely possible, and is done) that would be a step in the right direction. I'm with you on the 10 year plan depending on what the amp has in it already (any general purpose elko I would change... I would consider JJ, F&T, LCR Can replacements very niche general purpose). Most newer elko caps on the market have very long life expectancy, and better ESR/ESL specs, and you can find some that will last 20+ years without any degradation. Poly's on the other hand can last longer than than the builders life. A new fad is to use Motor run caps. Again will seldom need replacement for this purpose.



the post was more in reference to PT destruction, dried filter caps being the least likely cause of all things. had nothing to do with when you should replace them.




MartyStrat54 said:


> That if the amp sounds "okay" it is safe to play with old filter caps? With the volume cranked above 6? That if the filter cap shorts out "it probably won't damage anything?"
> 
> I respect my gear more than that. I didn't hesitate to get cap jobs. I'm one of those guys who actually believes in preventive maintenance. I really don't care if the damage could be slight or horrible. The bottom line is filter caps are supposed to be changed out approximately every ten years. I don't think I am going to get a nice tight tone at volume out of my amp with crappy filter caps.
> 
> Just my opinion.



said nothing of the sort, I said a dried filter cap is less likely to be the cause of *PT destruction* amongst the other more likely things, and that the amp will sound like complete shit, and be horribly noisy before it would likely cause a short, In which case that would be a huge indicator to take it in and get it serviced anyway. and that a series parallel arrangement will by nature have some preventive measures naturally by design. everytime I service an old amp I change out every elko in there, with low ESR/ESL, long life elko's suited to work ideally in way worse conditions than any guitar amp ever will see... I bet you most techs don't do that.

I also said this:

if you are concerned with preventive maintenance, have the amp modded to fuse both the heater winding, and the HT winding _at the winding_, (not after the plate supply) Heater shorts are far more likely to cause PT destruction, and some companies such as Peavey cover their asses by doing this amongst other preventive measurements they take in the initial design.


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## wkcchampion

What a thread!!!!! It should be put as a Sticky!
The first thing I checked in the recently acquired (and problematic) 1959 from 1981 were the caps. But they look new, they have been recently put in, probably 1 year ago


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## Wilder Amplification

Joey Voltage said:


> Now Jon. The only thing I'm going to say about the initial post is this: The PT is pretty hard to kill in a typical amp, and while it can be possible to harm it with a cap shorting due to age, it isn't the most likely of scenarios for PT destruction,* and would be even harder in the second illustration which uses a series parallel connection.*



Not necessarily. Each of the reservoir caps in the 100 watt FWB doubler circuit (yes I know, semantics ) is being switched between each 1/2 of the HT secondary depending on what cycle of the AC is on and which diodes are conducting at any given time. This means that if one of the two were to short it would short out whichever 1/2 of the HT winding that shorted cap happens to be on at any given time, again dictated via the AC cycle and the diode switching. Either way, shorting out 1/2 the winding is enough to fry a PT.




Joey Voltage said:


> Before the scenario of a dried up cap causing a short would take place, the amp would most likely sound, and feel like absolute crap!, and would be noisy enough to warrant servicing anyway, at which time the caps should be changed. and while I'm all on board, and gung ho about replacing elko's, I'm also not so quick as to jump to conclusions about PT failures. If you are so worried about any possible PT failures, fuse every goddamned tap like Peavey does, especially the heater supply, and call it an extra special mod



OK the point of the post was not to debate the exact probability be it high or low of the PT being taken out by a dried up filter cap that happens to short. The point of it was to illustrate the fact that caps DO dry up, that us techs aren't "just trying to sell more parts for the sake of selling more parts" as lots would like to believe when we recommend a cap job, and that the potential for a fried PT DOES in fact exist. PTs aren't cheap and the majority of guitar players cannot afford to replace them should they happen to fry. So anything you can do to minimize the risk of a blown PT (or OT for that matter, which is why routine power valve replacement is so important) is a step in the right direction when it comes to preventive maintenance.


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## rjohns1

Great info guys. I'm thinking my 6100 should get some new caps soon.


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## Joey Voltage

Wilder Amplification said:


> (yes I know, semantics )


 Ah, the infamous doubler, we already had that discussion a year ago. semantically you are right about that, and that is the one of the draw backs to that circuit, over the standard bridge, (no discharge path is the other). otherwise though it will offer better balancing than resistive balancing even. There is nothing wrong with adding a bleed path with that circuit.






Wilder Amplification said:


> OK the point of the post was not to debate the exact probability be it high or low of the PT being taken out by a dried up filter cap that happens to short. The point of it was to illustrate the fact that caps DO dry up, that us techs aren't "just trying to sell more parts for the sake of selling more parts" as lots would like to believe when we recommend a cap job, and that the potential for a fried PT DOES in fact exist. PTs aren't cheap and the majority of guitar players cannot afford to replace them should they happen to fry. So anything you can do to minimize the risk of a blown PT (or OT for that matter, which is why routine power valve replacement is so important) is a step in the right direction when it comes to preventive maintenance.



yeah, I'm with you on that aspect, that should be evident as I'm the one that has a reputation for cork sniffing when it comes to par spec, and reliability. My point was while it is a possibility (although low compared to others), It is also a possibility with *NEW* caps too, or brand spanken *NEW* valves, and that if you are looking for preventative measures, it is best to build in protection that is designed to actually stop something in these scenarios, instead of relying on the brand new parts to do it as your measure. Of course it never hurts!!! we are all on board with that.

A better scare tactic would be simply say your amp will be noisy, and it will sound like shit!, there that should make anybody come around.

By the way, I have never heard of people resisting filtration changes to the extent of what you listed, I don't know where you have been seeing this, I would like to have a look if you have a link. My debate with you had nothing to do with your post, just the selling point of the preventative measure aspect.


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## wkcchampion

Joey Voltage said:


> By the way, I have never heard of people resisting filtration changes to the extent of what you listed, I don't know where you have been seeing this, I would like to have a look if you have a link. My debate with you had nothing to do with your post, just the selling point of the preventative measure aspect.



I did and multiple times. To a certain extent, Wilder is right.


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## MartyStrat54

Joey Voltage said:


> yeah, I'm with you on that aspect, that should be evident as I'm the one that has a reputation for cork sniffing when it comes to par spec, and reliability. My point was while it is a possibility (although low compared to others), It is also a possibility with *NEW* caps too, or brand spanken *NEW* valves, and that if you are looking for preventative measures, it is best to build in protection that is designed to actually stop something in these scenarios, instead of relying on the brand new parts to do it as your measure. Of course it never hurts!!! we are all on board with that.



This makes sense and I agree with it. In fact I have stated that about tubes on the forum before. New tubes are not a guarantee and you are right, neither is new caps. It just "lessens" the odds. I do know that HP used to make some little 20 watt per channel EL84 stereo amps and they where some of the best built amps around. They were fused at all the critical points in the circuitry. I had two of them at one time and looking at each, I was amazed at how identical they looked, even though they had been made at different times and by different people. Ah, good old American craftsmanship.


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## core

Joey Voltage said:


> By the way, I have never heard of people resisting filtration changes to the extent of what you listed, I don't know where you have been seeing this, I would like to have a look if you have a link. My debate with you had nothing to do with your post, just the selling point of the preventative measure aspect.



Not sure if I have mentioned this on the forum, I may have but when I took my '77 JMP 2204 in for a checkup one of the things I asked my tech was whether I should do a full cap job. Not really knowing much about them and giving him my trust I told him to check them out and if they needed to be changed then by all means do so. When I got the amp back he said they were fine and in fact since it's in a vintage amp I should keep them in for the fact that they were made better back then and should last a long time. Again not being "in the know" what else can I go on when getting conflicting messages.

I can see this scenario happening a lot in the vintage circles. Personally to me it's just like changing a fuel filter on a vintage automobile. The filter may be new or at least made new to look vintage but it's a key component to make the auto run the best. You wouldn't put in the original filter just for the sake of a 100% correct restoration. That's ridiculous and harmful! 

After reading this, and I am grateful Jon for making clear light of it, I will be sending it back or most likely to another tech to do the job as I don't have the means and proper knowledge to form caps and such. Nor do I know what are the best ones out there for my amp.


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## Wilder Amplification

core said:


> Not sure if I have mentioned this on the forum, I may have but when I took my '77 JMP 2204 in for a checkup one of the things I asked my tech was whether I should do a full cap job. Not really knowing much about them and giving him my trust I told him to check them out and if they needed to be changed then by all means do so. When I got the amp back he said they were fine and in fact since it's in a vintage amp I should keep them in for the fact that they were made better back then and should last a long time. Again not being "in the know" what else can I go on when getting conflicting messages.
> 
> I can see this scenario happening a lot in the vintage circles. Personally to me it's just like changing a fuel filter on a vintage automobile. The filter may be new or at least made new to look vintage but it's a key component to make the auto run the best. You wouldn't put in the original filter just for the sake of a 100% correct restoration. That's ridiculous and harmful!
> 
> After reading this, and I am grateful Jon for making clear light of it, I will be sending it back or most likely to another tech to do the job as I don't have the means and proper knowledge to form caps and such. Nor do I know what are the best ones out there for my amp.



F&T are a high end brand cap. We put some in Marty's 2204 and are putting some in his 78 2203. A little cheaper but still good quality are the JJ filter caps. I've ran a batch of those in both my '69 SLP clones and they were run ballz out cranked for a 3 year stint and never had one fail.


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## Buggs.Crosby

say i was to do my own caps.....could they be formed...discharged then ship and installed without issues?....or do they have to hold some charge before actual use?...i ask because DSL's and the like have bleeders that discharge them correct?...so if they are discharged and recharged as in this case is it a bad thing?


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## core

Thanks, I thought I'd read you use F&T but wasn't sure. I know I should replace exactly what I have in there currently but what are the differences between a 50µF x 50µF / 500V and a 100µFx100µF / 500V. Why to use one over the other?


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## Wilder Amplification

Buggs.Crosby said:


> say i was to do my own caps.....could they be formed...discharged then ship and installed without issues?....or do they have to hold some charge before actual use?...i ask because DSL's and the like have bleeders that discharge them correct?...so if they are discharged and recharged as in this case is it a bad thing?



No they don't have to hold a charge for any length of time prior to normal use. Typically when I form caps, I remove all bleeders and the HT winding center tap (older 100 watters only), then install a 100K resistor between the HT rectifier and the first filter caps. I then hook my DMM across the 100K and watch the voltage drop on it. It starts out at like 200 something, then drops as the caps slow charge. I let them run like that until the voltage drop registers 5V or less. Once it's down to about there the caps are formed and ready for use.

The 100K basically just limits the charge current and allows them to slow charge rather than just up and throwing the voltage to 'em.



core said:


> Thanks, I thought I'd read you use F&T but wasn't sure. I know I should replace exactly what I have in there currently but what are the differences between a 50µF x 50µF / 500V and a 100µFx100µF / 500V. Why to use one over the other?



Bigger cap values for plate & screen filters = tighter filtering and less sag. Basically amounts to tighter lows when pushing the power section hard, but there is a limit to it. If the PA already stays tight when you push it the difference won't be as prominent as it would say on an earlier Marshall that used a lot less filtering than the standard 50+50uF caps.


----------



## nedcronin

Super cool thread.


----------



## Buggs.Crosby

nedcronin said:


> Super cool thread.



+1....i agree with Marco...this one should become a sticky....i know a little....this one just gave me a lot with very few posts...bravo boys (and yes i can say Boys you little window dressing panty washers) as Major would say


----------



## Lane Sparber

Buggs.Crosby said:


> ...so if they are discharged and recharged as in this case is it a bad thing?



To answer this part of your question, Buggs, although we often compare filter caps to batteries for demonstrative purposes, these caps' internal workings are NOT like batteries in the sense that as long as their electrolytes are intact, they can be charged and drained indefinitely with no damage.  In fact, that's what happens every time you turn on your amp! 

-Lane


----------



## charveldan

Got my 2203 back with F&T Filter caps & Sprague bias filters, gave it a test drive, THE AMP HAS BALLS!!!!! And the more you turn it up the Hairier they get, theres more gain on tap too.

Super creamy mid-range with plenty of low-end thump, a worthy upgrade.


----------



## Buggs.Crosby

Lane Sparber said:


> To answer this part of your question, Buggs, although we often compare filter caps to batteries for demonstrative purposes, these caps' internal workings are NOT like batteries in the sense that as long as their electrolytes are intact, they can be charged and drained indefinitely with no damage. In fact, that's what happens every time you turn on your amp!
> 
> -Lane



That i know....just was not sure after initial forming how long it should hold it's charge before it is fully discharge....kinda like the battery theory i or like a burn in time i guess


----------



## MartyStrat54

charveldan said:


> Got my 2203 back with F&T Filter caps & Sprague bias filters, gave it a test drive, THE AMP HAS BALLS!!!!! And the more you turn it up the Hairier they get, theres more gain on tap too.
> 
> Super creamy mid-range with plenty of low-end thump, a worthy upgrade.



That's why I insisted on cap jobs for my 2204 and 78 2203. I want hairy balls.


----------



## Buggs.Crosby

MartyStrat54 said:


> I want hairy balls.



May i recommend an Italian?


----------



## Wilder Amplification

I find guitarists to be a funny bunch. It's like if you tell them that not changing out certain aged components can kill their amp they could give a shit less.

But tell them that those components will kill their tone and they're all over it.


----------



## Bieling3

Besides bulging, visible leakage, and increased 60 cycle hum (damn, that was starting to sound like a porn movie description for a second) what is the best way to determine the health of your filter caps?


----------



## Buggs.Crosby

*Re: Winston also*



gjhffgkj said:


> Winston also wow gold got up and finished himself. The tireless line herb on: 'They sye that measure 'eals all things, They sye you can e'er lose; But the smiles an' the tears acrorss the life They development my 'eart-strings yet!' As he pinned the blow of his overalls he wow gold strolled across to the window.



Spam Reported


----------



## Adwex

No need to quote the spam, just report it.


----------



## Wilder Amplification

Adwex said:


> No need to quote the spam, just report it.



I was trying to sell filter caps...does that count?


----------



## TwinACStacks

Jon should I be considering new caps in the 1999 DSL they are single section Radials, what brand is highest quality for these?

 TWIN


----------



## Buggs.Crosby

Adwex said:


> No need to quote the spam, just report it.



just making sure people knew what i was reporting.....don't want them to think it was something they posted


----------



## Lane Sparber

Wilder Amplification said:


> I find guitarists to be a funny bunch. It's like if you tell them that not changing out certain aged components can kill their amp they could give a shit less.
> 
> But tell them that those components will kill their tone and they're all over it.



+10000 That's probably the most common misconception I have to deal with here. 

Also - Buggs, once they're formed, they are IMMEDIATELY at full function and ready to go. I hope that answer was what you were looking for. 

-Lane


----------



## Lane Sparber

Bieling3 said:


> Besides bulging, visible leakage, and increased 60 cycle hum (damn, that was starting to sound like a porn movie description for a second) what is the best way to determine the health of your filter caps?



The amp could lose punch, and also lose bass frequencies. Also, on certain high notes (try a Bb on the G string 15th fret) at high volumes, you can get an odd harmonic or "ghost note" that sounds horrible. This harmonic may or may not follow the notes around. Basically, if your amp is over 10 years old, just CHANGE THOSE CAPS! 

-Lane


----------



## Marshall Mann

OK guys, a question.

Is I there a sure fire way to test a cap (say, with a multi meter?) for the back yard mechanic? what would the specs be? How would the average user know if the caps in his head were bad and needed replacing other than relying on a tech or the "10 year plan"?


----------



## Wilder Amplification

Jesus Christ...are we all really that fucking cheap!? Not to be an asshole, but it's like you guys wanna get every last 1/4 mile out of your spark plugs that you possibly can! Just change them out every 10-15 years! Done deal! What the hell is $150 parts + labor every 10-15 years? That's like a whole whopping $10-$15 a year!


----------



## MM54

Here's another question - in dissecting (and/or fixing) various things, I've found quite a few caps that at first I thought were normal electrolytic, but are labeled "Dry Electrolytic." If they are already dry, they wouldn't die like other electrolytic caps, no? What hasn't this technology taken over?


----------



## Marshall Mann

Wilder Amplification said:


> Jesus Christ...are we all really that fucking cheap!? Not to be an asshole, but it's like you guys wanna get every last 1/4 mile out of your spark plugs that you possibly can! Just change them out every 10-15 years! Done deal! What the hell is $150 parts + labor every 10-15 years? That's like a whole whopping $10-$15 a year!



Hey Jon, this was a bit of a loaded question.

So, I buy a 1990 JCM head. How do I know (as an average user) if the caps have been replaced or not? How would I test the caps to be sure they were good?


----------



## Wilder Amplification

Marshall Mann said:


> Hey Jon, this was a bit of a loaded question.
> 
> So, I buy a 1990 JCM head. How do I know (as an average user) if the caps have been replaced or not? How would I test the caps to be sure they were good?



Ah OK...now I got ya.

Typically the 900s are still considered "newer Marshalls" so chances are nobody has ever thought to change them out. But...if they've got LCRs in them still, I'd bet they're factory.

However if they've got F&Ts or JJs in them and they look pretty new and aren't all dusty n' shit, Marshall never used F&T or JJ caps so they would have to be aftermarket.


----------



## Lane Sparber

Also...isn't L.C.R. out of business (or at least no longer making those caps)? I thought I'd heard that somewhere...

-Lane


----------



## Marshall Mann

Wilder Amplification said:


> Ah OK...now I got ya.
> 
> Typically the 900s are still considered "newer Marshalls" so chances are nobody has ever thought to change them out. But...if they've got LCRs in them still, I'd bet they're factory.
> 
> However if they've got F&Ts or JJs in them and they look pretty new and aren't all dusty n' shit, Marshall never used F&T or JJ caps so they would have to be aftermarket.



Thanks Jon! 

But is there a way to put a multi meter (or some other test) to a cap and tell if it's out of spec?


----------



## Wilder Amplification

Marshall Mann said:


> Thanks Jon!
> 
> But is there a way to put a multi meter (or some other test) to a cap and tell if it's out of spec?



No because multimeters cannot test them anywhere NEAR the voltage that a valve amp power supply puts to 'em. Furthermore I don't know of any piece of test equipment that WOULD test them at real amp voltages other than a valve amp power supply.

@Lane...that's exactly why I mentioned LCR.


----------



## MM54

(This a reminder to my question back in post #55)


----------



## Marshall Mann

Wilder Amplification said:


> No because multimeters cannot test them anywhere NEAR the voltage that a valve amp power supply puts to 'em. Furthermore I don't know of any piece of test equipment that WOULD test them at real amp voltages other than a valve amp power supply.
> 
> @Lane...that's exactly why I mentioned LCR.



Thanks Jon!


----------



## Marshall Mann

Bump



> MM54 - Here's another question - in dissecting (and/or fixing) various things, I've found quite a few caps that at first I thought were normal electrolytic, but are labeled "Dry Electrolytic." If they are already dry, they wouldn't die like other electrolytic caps, no? What hasn't this technology taken over?


----------



## Kunnz

Wilder Amplification said:


> The top schematic is the typical JCM800 50 watt power supply while the bottom schematic is the typical 6 filter cap version of the JCM800 100 watt power supply. If you look closely, the HT fuse is DOWNSTREAM of that very first filter cap, which we'll call the "reservoir cap". This cap sustains a high load as the output valves draw lots of current from it as well as the rest of the amp so this particular filter cap sustains the highest load out of all of the filter caps in the amp. The power transformer acts as the "alternator" which continuously recharges the cap for as long as the power transformer is on.
> 
> If that cap were to short, the ONLY fuse protection it has is from the mains fuse since that cap is upstream of the HT fuse. This means that the power transformer has to sustain a high current load for the length of time it takes to blow the mains fuse. In a perfect world, this would only last a second or two as it would only take that long to pop the mains fuse. However, nothing is perfect and as such fuses are not a 100% fail safe device. Sometimes they don't blow right away. In that scenario, you can pretty much kiss your power transformer goodbye.
> 
> Now this isn't to say that "if you short a reservoir cap it's 100% guaranteed to blow your PT". Nothing is absolute, sometimes you get lucky, yada yada yada. But the risk factor of such is GREATLY increased by choosing to run those old dried up original filter caps.
> .



Ok Jon that's a very good example and informative.

A quick question here. On my 1969/1970 Marshall JMP superlead there are two 0.22uF non electrolytic caps up-stream of the FWBR connected series to each side of the PT, please see page 3 of; 

http://www.schematicheaven.com/marshallamps/jmp_superlead_100w_1959.pdf


The schematic is not exact but close as these caps are actually located between the standby switch and the FWBR in the circuit.

Are these acting as inrush current limiters to protect the FWBR and the rest of the components on the HT line when the standby is switched?


BTW *MartyStrat,* old blackened bananas are nice on toast.


----------



## jcmjmp

Wilder Amplification said:


> Take a look at the two schematics shown below -
> 
> _... snip ..._
> 
> If you look closely, the HT fuse is DOWNSTREAM of that very first filter cap, which we'll call the "reservoir cap".
> 
> _... snip ..._
> 
> If that cap were to short, the ONLY fuse protection it has is from the mains fuse since that cap is upstream of the HT fuse. This means that the power transformer has to sustain a high current load for the length of time it takes to blow the mains fuse. In a perfect world, this would only last a second or two as it would only take that long to pop the mains fuse. However, nothing is perfect and as such fuses are not a 100% fail safe device. Sometimes they don't blow right away. In that scenario, you can pretty much kiss your power transformer goodbye.



Does this mean we should add fuses before/after every single power supply filter cap? LOL!


----------



## Wilder Amplification

Kunnz said:


> Ok Jon that's a very good example and informative.
> 
> A quick question here. On my 1969/1970 Marshall JMP superlead there are two 0.22uF non electrolytic caps up-stream of the FWBR connected series to each side of the PT, please see page 3 of;
> 
> http://www.schematicheaven.com/marshallamps/jmp_superlead_100w_1959.pdf
> 
> 
> The schematic is not exact but close as these caps are actually located between the standby switch and the FWBR in the circuit.
> 
> Are these acting as inrush current limiters to protect the FWBR and the rest of the components on the HT line when the standby is switched?
> 
> 
> BTW *MartyStrat,* old blackened bananas are nice on toast.



Hey Kunnz. Those are "snubber" caps and they're there to filter transient spikes out of the HT secondary. Some Marshalls had them while others did not.

I could see where they could reak havoc on a secondary winding if one of those happened to short. Although I personally have never seen that happen, this isn't to say that it's not possible to or that it never has...it just means I have never personally seen it happen. When in doubt, change 'em out. 

At 60Hz they provide the equivalent of a 12K ohm load across each 1/2 of the secondary winding (capacitive reactance for a 0.22uF cap @ 60Hz = 12K ohms). This translates to a 14.5mA draw off the HT winding.



jcmjmp said:


> Does this mean we should add fuses before/after every single power supply filter cap? LOL!



I thought that's how y'all roll in Canada.


----------



## kebek

when you have a vintage camaro 1969... you do change the oil brake pads... broken parts but it is still a camaro 1969...


----------



## MartyStrat54

From the Internet. A non-biased opinion.

Don't try to examine or change filter caps unless you know how to drain them. They store electricity, even when the amp is unplugged! They will hurt you!

Filter capacitors are part of the power supply and bias supply in a guitar amp. They need to be changed after a certain number of years. Any amp 15 years old or more should have the filter capacitors changed.

Filter capacitors dry out after time. They can cause an amp to have "ghost notes". These occur when the capacitance in the power supply gets reduced. Some people like this tone, but it is usually a sign of an old and possibly ready to fail filter capacitor. Some newer amps are designed to give this tone. Another problem that old filter capacitors can cause is leaking your plate voltage to ground. This will give you less power and punch. Some people like this, but it is a sign of an old and possibly ready to fail filter capacitor once again. Sometimes you will hear a very strange version of tremolo or vibrato in your amp. This can be a sign of a bad bias filter cap. If the bias filter cap shorts out, you will burn up your power tubes! The bias supply capacitor needs to be changed too!

What happens when a filter capacitor fails? They can short out which can do a few things. If you have the correct size fuse in your amp, the fuse will probably blow and when you put in a new fuse, it will blow it again. If you try changing all the tubes in the amp (all of them!) and the fuse still blows, you very likely have a shorted filter cap. If you have too big a fuse in your amp (or a bunch of tin foil shoved in the fuse socket like I've seen a million times), your high voltage secondary will blow on the power transformer. This is a very expensive mistake. Don't use anything but the correct value fuse for your amp! Filter caps can also lose their filtering function with time, leaving your amp with less filtering than it needs to operate properly. Symptoms of decreased power supply filtering are hum, buzz, motorboating, loss of power, and strange noises.

Some people complain that the tone of their amp was lost when the filter caps got changed. In reality, that tone that they were getting was due to bad or failing filter caps and that tone should have never been there in the first place! There are some people that will advise you that changing the filter caps will "kill" your tone or that if you like the tone of your amp now, then the filter caps should not be changed. These people may also say that changing the filter caps will devalue your vintage amp. This is not good advice. Let me give a few analogies. You say that you like the way your car handles. But the tire pressures are at 5psi. This is your opinion of what a good handling car is. Is this a reasonable opinion? No! Get the pressures right or you're going to throw the carcass right off the tire! You say that your car has been running fine and you think you don't need to do anything to it. Is this any excuse not to get the oil or spark plugs changed? No! Filter caps are like changing the oil or tires on a car. It just needs to get done. People are spoiled by modern equipment that doesn't need service. Old amps need service, and after a certain amount of time, the filter capacitors need to be changed.


----------



## RickyLee

OK fellas - a filter cap question.

How about this situation. Let's say you have an amp that it's filter caps are fairly new or even anywhere from fairly new up to 5 years old. And you change the power transformer out on this amp. The old PT was giving you a B+ of 450V and now your new PT is giving you a higher B+ of let's say 475V. Do you now have to replace those filter caps as well? 

Or how about if the situation is reversed where the new PT is giving you a lower B+??


----------



## Lane Sparber

As long as the filter caps are rated for the voltages involved, then no replacement is necessary. A standard 500v filter cap will work fine for BOTH of those voltages.

-Lane


----------



## MM54

Is my question being avoided ?



Me said:


> Here's another question - in dissecting (and/or fixing) various things, I've found quite a few caps that at first I thought were normal electrolytic, but are labeled "Dry Electrolytic." If they are already dry, they wouldn't die like other electrolytic caps, no? What hasn't this technology taken over?


----------



## MartyStrat54

Lane Sparber said:


> As long as the filter caps are rated for the voltages involved, then no replacement is necessary. A standard 500v filter cap will work fine for BOTH of those voltages.
> 
> -Lane



Lane I've discussed this with Jon. Aren't the main filter caps connected in such a manner so that they are actually rated at 1000 volts? (Using 500V caps.)


----------



## Lane Sparber

MartyStrat54 said:


> Lane I've discussed this with Jon. Aren't the main filter caps connected in such a manner so that they are actually rated at 1000 volts? (Using 500V caps.)



I wasn't speaking about a specific wiring scheme here, Marty. Ricky was asking a pointed question about certain voltages and what to do. I was answering his specific question.

Yes, you are correct in that in some Marshalls (with the first two filter caps in SERIES), the first filters are wired to be rated at 1000v, but that wasn't Ricky's question, I believe. He said AN amp...not a MARSHALL amp specifically. A standard, single 500v cap will work for both voltages he postulated above. If the filters in question are the MAIN filter caps, then yes, I should add that with those voltages it would be safest to wire two in series for the 1000v rating, although it would cut the capacitance in half, which is why higher value caps are sometimes used in these applications.

-Lane


----------



## Wilder Amplification

MartyStrat54 said:


> Lane I've discussed this with Jon. Aren't the main filter caps connected in such a manner so that they are actually rated at 1000 volts? (Using 500V caps.)



On 100 watters that use the FWB doubler circuit, the first two caps along with the screen caps are in series so this doubles their voltage handling. 50 watt Marshalls never used a FWB doubler circuit or a series stack scheme on the first filters though.


----------



## Lane Sparber

Wilder Amplification said:


> On 100 watters that use the FWB doubler circuit, the first two caps along with the screen caps are in series so this doubles their voltage handling. 50 watt Marshalls never used a FWB doubler circuit or a series stack scheme on the first filters though.



See? Just as I said above...it all depends on the amp in question! 

-Lane


----------



## Bieling3

MM54 said:


> Is my question being avoided ?



I got that feeling with my question too. Although Marty kind of answered it with that last post. I must be on certain peoples ignore list still.


----------



## Lane Sparber

Bieling3 said:


> I got that feeling with my question too. Although Marty kind of answered it with that last post. I must be on certain peoples ignore list still.



Check post #52, sir! 

-Lane


----------



## Bieling3

Thank you, Sir. Between that and Marty's post I don't think my issue is with the filter caps then.


----------



## RickyLee

What I was getting at is an issue that I read on the net regarding filter cap "forming", or electrolytic cap "forming" in general - which must have been B.S. being you guys did not bring it up. I had read that an e'lytic cap gets used to a particular voltage range after a bit of time. That is why I asked about the scenario of running filter caps at an aprox. range of voltage and then changing it by 25V, 50V ect.

Anyone??


----------



## TwinACStacks

TwinACStacks said:


> Jon should I be considering new caps in the 1999 DSL they are single section Radials, what brand is highest quality for these?
> 
> TWIN



Bump

Still would like to know what are the best Quality caps for the DSL?

 TWIN


----------



## Sir Don

The more I read here the more depressed I am becoming! I've got half a dozen amps that would need caps replaced, only my 1959 has had them done.


----------



## jcmjmp

RickyLee said:


> What I was getting at is an issue that I read on the net regarding filter cap "forming", or electrolytic cap "forming" in general - which must have been B.S. being you guys did not bring it up. I had read that an e'lytic cap gets used to a particular voltage range after a bit of time. That is why I asked about the scenario of running filter caps at an aprox. range of voltage and then changing it by 25V, 50V ect.
> 
> Anyone??



New filter caps don't need to be formed. Old caps that have been sitting on the shelf (or in an amp) for *extended* periods of time probably need to be formed.


----------



## RickyLee

jcmjmp said:


> New filter caps don't need to be formed. Old caps that have been sitting on the shelf (or in an amp) for *extended* periods of time probably need to be formed.



So filter caps don't retain a "memory" over time, and want to keep seeing that aprox. range of voltage. 

Sorry guys LOL I ran into some odd info on the net quite some time ago and I want THE TRUTH!

LOL


----------



## core

jcmjmp said:


> New filter caps don't need to be formed. Old caps that have been sitting on the shelf (or in an amp) for *extended* periods of time probably need to be formed.



Wait hold on, If I go out and buy new filter caps, say F&T, they don't need to be formed? I'm confused as you guys have said in other statements and posts that they DO need to be formed before installing them unless I'm misunderstanding. Some sites that sell them say they are pre-formed where other sites such as TubeStore don't make any mention of it. It's very confusing and it makes us guys here who could do the work ourselves, if it was that easy, not want to for fear of getting something wrong. 

For routine maintenance I believe we should be able to do certain tasks ourselves. I do on my car why can't I on this? I mean I should be able to swap out new tubes and caps and do general cleanup and such but we're kinda at the mercy of you guys here, conflicting or incomplete information doesn't really help. And I know you guys spent a lot of time learning this stuff, it's your trade but there's a plethora of auto maintenance books out there and I still have to take my car to the mechanic once in awhile.

My point is I'd love to change the caps myself but when Jon gives a detailed explanation of what he does to form caps, which to my layman ears is way too confusing to attempt, it tells me I should take it back in and have the job done. But then you say you don't need form new caps, what are we supposed to do?

$10 a cap is not much, my amp has 3 but add labor (would be nearly $100 total) and a week turnaround with my local guy it's not very attractive. With all due respect, I hope you see my point.


----------



## Lane Sparber

RickyLee said:


> So filter caps don't retain a "memory" over time, and want to keep seeing that aprox. range of voltage.
> 
> Sorry guys LOL I ran into some odd info on the net quite some time ago and I want THE TRUTH!
> 
> LOL



NO - there is no "Memory" with filter caps. Now I see where you were coming from. Caps are NOT, and I repeat, NOT batteries!

Core- opinions seem to be split regarding forming. Wilder does it (see his method somewhere above), I do it, JCM apparently doesn't and that's fine. It's kind of a subjective thing. I used to NOT do it, but I form the caps now mainly so I can keep an eye on them for any problems at start-up and to put some hours on them before I give the amp back to the customer. Purely F.Y.I. - here's my method, and while not as involved with the internal workings of the amp (soldering and un-soldering) as Jon's, it does involve a Variac, so be warned. There are pros and cons of each method.

I power up the amp at 40v on the Variac, and leave it overnight. Then, the next day, I raise the voltage 10v every hour, and at the end of that 8 hour day it's at 120v. That's just how I do it, but it CAN be done much faster. Keep in mind that you're working with (arguably) the most dangerous components in the amp when you do a filter cap job, and that's why most techs don't recommend a novice trying to do this procedure without a THOROUGH knowledge of the safety measures involved.

TwinAC - I use Nichicon radial caps when I do a cap job. They are the only ones that have proven themselves stable and reliable to me over time. Just my $.02.

-Lane


----------



## TwinACStacks

Thanx Lane. Any particular specs I need to be concerned about?

 TWIN


----------



## Lane Sparber

TwinACStacks said:


> Thanx Lane. Any particular specs I need to be concerned about?
> 
> TWIN



Not really...I usually try to put in the largest (in physical size, that is!) replacement caps that I can and still have them fit on the board. Remember to try and keep to the original value uf (microfarad) rating of the cap, but you can use a HIGHER voltage rating if you need to. For example, a 470uf/25v radial cap CAN be replaced by a 470uf/35v cap as long as it fits. Just don't use a cap rated for a LOWER voltage than the original cap, and you'll be fine. 

It's also worth noting that if the original caps were hot-glued to the board, you can use a #11 X-Acto knife to GENTLY AND DELICATELY break the bonds. Finally, when you mount the new caps, you should hot-glue them in just like the old ones were.

-Lane


----------



## Wilder Amplification

jcmjmp said:


> New filter caps don't need to be formed.



Ah...to live in a perfect world.



core said:


> Wait hold on, If I go out and buy new filter caps, say F&T, they don't need to be formed? I'm confused as you guys have said in other statements and posts that they DO need to be formed before installing them unless I'm misunderstanding. Some sites that sell them say they are pre-formed where other sites such as TubeStore don't make any mention of it. It's very confusing and it makes us guys here who could do the work ourselves, if it was that easy, not want to for fear of getting something wrong.



In a perfect world, no they wouldn't need to be formed. However, fact of the matter is that unless there's a date code you have no idea as to how "new" they are, and furthermore just because a component is "new" doesn't mean there isn't something internally wrong with it. Putting new caps through the forming process upon installation allows you to find out if the cap is any good or not under safe controlled conditions. If there's a problem with the cap more than likely it will rear its ugly head at a much lower charge voltage than the amp's B+ and you'll be able to see it on the meter before any real major damage occurs to other stuff. Kinda like installing a light bulb in series with the mains as a current limiter on a SS amp under test that's just been repaired. 

As an example, MajorNut built a JCM800 clone a few months back and had a brand new filter cap blow up on him while he was pre-forming them so it can and does happen.



core said:


> For routine maintenance I believe we should be able to do certain tasks ourselves. I do on my car why can't I on this? I mean I should be able to swap out new tubes and caps and do general cleanup and such but we're kinda at the mercy of you guys here, conflicting or incomplete information doesn't really help. And I know you guys spent a lot of time learning this stuff, it's your trade but there's a plethora of auto maintenance books out there and I still have to take my car to the mechanic once in awhile.



Yes but does your car run on a supply of 400-450V? Can your car blow up a bunch of expensive parts after changing oil (yes but only if you forget to put oil in it afterwards prior to starting), air cleaner or spark plugs?



core said:


> My point is I'd love to change the caps myself but when Jon gives a detailed explanation of what he does to form caps, which to my layman ears is way too confusing to attempt, it tells me I should take it back in and have the job done.



For those of us who know electronics theory, it's not confusing at all. This is because we understand what the method does and how it does it. IMHO, if someone cannot figure out something as simple as installing a resistor in line with a rectifier and a filter cap, removing bleeder resistors and disconnecting the HT secondary CT from the first filter caps, they shouldn't be working anywhere NEAR a valve amp power supply. 

I don' t say these things to be condescending in any way shape or form. I say them because of the safety factor involved with amps and due to the all too common perception that most guitarists have of us techs having this "elitist" attitude yet it's not that at all. I see lots of you guys complain "Well I wanna fix my own stuff to save money too", "You weren't born working on amps", etc etc yet everyone of you seem to think that we just jumped in blindfolded and started working on amps when it's actually quite the contrary. Those of us who know in detail what we're doing and how and why certain things work the way they do put the time and effort in to learn some electronics and amp theory. They say "Give a man a fish and he'll eat for a day. Teach a man to fish and he'll eat for a lifetime". It seems this day and age we try to teach you all this stuff, but no one wants to learn it...they'd much rather just have us "give them a fish".

Believe it or not, amps are simple electrical devices. Electrons flows the same way in an amp circuit as it would in any other circuit. Ohm's and Watt's Law applies to amp circuits just like any other circuit. It's basically just a modulated DC power supply...a "power inverter" if you will. The problem is that most guitarists approach amps from the "tone" perspective while failing to even see the electrical perspective and this is why most guitarists cannot grasp it right out the gate. When you're first learning amps, if you just simply forget about tone or even the fact that amps have anything to do with audio at all and look at it as a simple modulated DC power supply, they become quite easy to understand. It's just like hot rod guys thinking only in terms of "horsepower" while completely discounting "torque", when horsepower is just a calculated amount of work performed by torque and RPM combined. Horsepower is just an interesting afterthought....just like "tone" is for amps. But trying to get guitarists to do this sometimes is like pulling teeth...they're all OCD about tone. 



core said:


> But then you say you don't need form new caps, what are we supposed to do?



Again, we live in an imperfect world. There are few absolutes and seemingly infinite exceptions. Putting new caps through the forming process is a good safe way to slowly bring them up to voltage while also being able to tell if one cap is a bad one at a safer working voltage.



core said:


> $10 a cap is not much, my amp has 3 but add labor (would be nearly $100 total) and a week turnaround with my local guy it's not very attractive. With all due respect, I hope you see my point.



$100 total is worth MUCH more than adding that on top of the cost of a new PT to replace the one that fried due to a dried up filter cap that shorted + the labor to replace it. And for that matter, I would hope your life is worth much more to you than $100 + a couple weeks turnaround time.


----------



## Lane Sparber

MM54 said:


> Here's another question - in dissecting (and/or fixing) various things, I've found quite a few caps that at first I thought were normal electrolytic, but are labeled "Dry Electrolytic." If they are already dry, they wouldn't die like other electrolytic caps, no? What hasn't this technology taken over?



Matt - Rest assured you were NOT being ignored.  For my part, I just wanted to be sure and do some research before posting. To that end, I asked one of the senior engineers at work about this, and he said that ALL electrolytic capacitors are considered "dry" in engineer terminology, simply because the electrolyte is a moist paste and not PURE liquid which would require an air-tight seal (like a foil-in-oil cap). Any electrolytic cap made since the 50s is considered "dry," and older caps might be labeled as such to distinguish them from other types in the "good old days." To re-iterate, the aforementioned paste DOES contain moisture and WILL dry out, as Wilder, others and myself have been saying - it's just not LIQUID. I hope this makes sense to you.

-Lane


----------



## core

Wilder Amplification said:


> Ah...to live in a perfect world.
> 
> 
> In a perfect world, no they wouldn't need to be formed. However, fact of the matter is that unless there's a date code you have no idea as to how "new" they are, and furthermore just because a component is "new" doesn't mean there isn't something internally wrong with it. Putting new caps through the forming process upon installation allows you to find out if the cap is any good or not under safe controlled conditions. If there's a problem with the cap more than likely it will rear its ugly head at a much lower charge voltage than the amp's B+ and you'll be able to see it on the meter before any real major damage occurs to other stuff. Kinda like installing a light bulb in series with the mains as a current limiter on a SS amp under test that's just been repaired.
> 
> As an example, MajorNut built a JCM800 clone a few months back and had a brand new filter cap blow up on him while he was pre-forming them so it can and does happen.
> 
> Thanks Jon for the clarifications. Put that way it makes perfect sense since you can't ever really tell when they were made and if they are going to handle a charge properly. This seems to be in my case one of the OTHER than routine maintenance jobs. This is the kind of hard facts info I was looking for out of this thread
> 
> 
> Yes but does your car run on a supply of 400-450V? Can your car blow up a bunch of expensive parts after changing oil (yes but only if you forget to put oil in it afterwards prior to starting), air cleaner or spark plugs?
> 
> Well as an aside I've had a brand new Holly carb blow fire out the top on me due to failed diaphragm. Not good! LOL.
> 
> I may be wrong but I think you're missing my point. JCM made it seem to be as easy as swapping out a fuel filter. Now I could learn how to do it but to my other point some things are better left to the experts and now in this case that is cleared up.
> 
> 
> For those of us who know electronics theory, it's not confusing at all. This is because we understand what the method does and how it does it. IMHO, if someone cannot figure out something as simple as installing a resistor in line with a rectifier and a filter cap, removing bleeder resistors and disconnecting the HT secondary CT from the first filter caps, they shouldn't be working anywhere NEAR a valve amp power supply.
> 
> I don' t say these things to be condescending in any way shape or form. I say them because of the safety factor involved with amps and due to the all too common perception that most guitarists have of us techs having this "elitist" attitude yet it's not that at all. I see lots of you guys complain "Well I wanna fix my own stuff to save money too", "You weren't born working on amps", etc etc yet everyone of you seem to think that we just jumped in blindfolded and started working on amps when it's actually quite the contrary. Those of us who know in detail what we're doing and how and why certain things work the way they do put the time and effort in to learn some electronics and amp theory. They say "Give a man a fish and he'll eat for a day. Teach a man to fish and he'll eat for a lifetime". It seems this day and age we try to teach you all this stuff, but no one wants to learn it...they'd much rather just have us "give them a fish".
> 
> Believe it or not, amps are simple electrical devices. Electrons flows the same way in an amp circuit as it would in any other circuit. Ohm's and Watt's Law applies to amp circuits just like any other circuit. It's basically just a modulated DC power supply...a "power inverter" if you will. The problem is that most guitarists approach amps from the "tone" perspective while failing to even see the electrical perspective and this is why most guitarists cannot grasp it right out the gate. When you're first learning amps, if you just simply forget about tone or even the fact that amps have anything to do with audio at all and look at it as a simple modulated DC power supply, they become quite easy to understand. It's just like hot rod guys thinking only in terms of "horsepower" while completely discounting "torque", when horsepower is just a calculated amount of work performed by torque and RPM combined. Horsepower is just an interesting afterthought....just like "tone" is for amps. But trying to get guitarists to do this sometimes is like pulling teeth...they're all OCD about tone.
> 
> 
> 
> Again, we live in an imperfect world. There are few absolutes and seemingly infinite exceptions. Putting new caps through the forming process is a good safe way to slowly bring them up to voltage while also being able to tell if one cap is a bad one at a safer working voltage.
> 
> 
> 
> $100 total is worth MUCH more than adding that on top of the cost of a new PT to replace the one that fried due to a dried up filter cap that shorted + the labor to replace it. And for that matter, I would hope your life is worth much more to you than $100 + a couple weeks turnaround time.
> 
> My above post may have cleared up my point but if not I was simply referring to, in my case I don't mind spending money to have my amp running perfect. It's a wise investment. I'm not one of "those" guitarists. I can find my tone out of the amp and in fact I think people spend too much time arguing and worrying about the perfect tone. I'd rather have it running properly but when JCM made it seem so easy to do would you spend more money than you need to on something you can do yourself? Hopefully you can see where I'm coming from.



Please above my comments in yellow.


----------



## jcmjmp

Lane Sparber said:


> Core- opinions seem to be split regarding forming. Wilder does it (see his method somewhere above), I do it, JCM apparently doesn't and that's fine. It's kind of a subjective thing. I used to NOT do it, but I form the caps now mainly so I can keep an eye on them for any problems at start-up and to put some hours on them before I give the amp back to the customer.



I agree with Lane on giving the new caps some "burn in" time. 

As for forming, ask the manufacturer if they should be formed - 100% of the time, they'll say no. They're pre-formed at the factory (which wasn't always the case). This reminds me of when diskette manufacturers had pre-formatted disks and people could just use 'em out of the box. Would you waste your time re-formatting them? No. It was a great time saver.


----------



## jcmjmp

TwinACStacks said:


> Bump
> 
> Still would like to know what are the best Quality caps for the DSL?
> 
> TWIN



I'm putting together some filter cap kits for the DSL. I'll be getting Panasonic caps (I forget which model right now). They seem to have the best quality and life.


----------



## jcmjmp

Wilder Amplification said:


> As an example, MajorNut built a JCM800 clone a few months back and had a brand new filter cap blow up on him while he was pre-forming them so it can and does happen.



And forming them or not would not have made a difference. You just proved that forming is useless for new caps. So many techs out there want to make things more complicated than they really are, and that bugs me.

Monitoring the caps for the first 5-6 hours is a good idea, but really, that's all you need to do, for new caps.


----------



## jcmjmp

Core - I never said anyone without proper electronics training should replace filter caps. Don't put words in my mouth.


----------



## Wilder Amplification

jcmjmp said:


> And forming them or not would not have made a difference.



You're correct in the regard that it would've blown up regardless. But could you imagine the amount of damage that could've been done had he had just thrown full voltage to that cap vs slow charging them and having it happen at a much lower voltage?



jcmjmp said:


> So many techs out there want to make things more complicated than they really are, and that bugs me.



Doesn't bug me in the slightest. Just ensures that you're covering all bases and doing everything you possibly can to minimize the possibility of catastrophic failure.


----------



## jcmjmp

Wilder Amplification said:


> You're correct in the regard that it would've blown up regardless. But could you imagine the amount of damage that could've been done had he had just thrown full voltage to that cap vs slow charging them and having it happen at a much lower voltage?
> 
> 
> 
> Doesn't bug me in the slightest. Just ensures that you're covering all bases and doing everything you possibly can to minimize the possibility of catastrophic failure.



I've seen caps explode - I know what happens when they blow. The key thing is to take proper precautions when installing new parts in anything, not only amps.


----------



## charveldan

School me on "burn-in time" for caps, ive got fresh caps in a 100 watt JMP Marshall put in last friday.


----------



## core

jcmjmp said:


> Core - I never said anyone without proper electronics training should replace filter caps. Don't put words in my mouth.



I'm not putting words into your mouth. When you stated caps don't need to be formed it makes it seem like anyone who knows how to drain caps and can competently use a soldering iron is capable of replacing them. But Jon points out that there could be much more to it on a safety factor than that. That's all.


----------



## core

jcmjmp said:


> The key thing is to take proper precautions when installing new parts in anything, not only amps.



And if you had posted this in post #82 there's be no confusion


----------



## jcmjmp

core said:


> And if you had posted this in post #82 there's be no confusion



My comment in post #82 only says that forming _new_ caps is not necessary. I never said anything about just anyone doing this job on their own. 

You're assuming and/or interpreting things from I don't know where.


----------



## MartyStrat54

Can anyone join in, or do I need a baseball bat?

Really fellars, do we need to make a big issue about forming caps. I say if the tech feels better about doing it, great. Your momma baked cookies different than the lady down the street, but they didn't argue about it.

Capacitors are a lot different than current production tubes. You almost have to assume that one or two tubes might be bad in an order. Capacitors are more reliable and of course the good one's are not made in China. That means a lot. However, it does not mean that the filter cap is 100 percent good every time.

If someone wants to form the cap, it's their time and I say go right ahead.


----------



## TwinACStacks

jcmjmp said:


> I'm putting together some filter cap kits for the DSL. I'll be getting Panasonic caps (I forget which model right now). They seem to have the best quality and life.



Cool JC Let me Know.

 TWIN


----------



## Lane Sparber

charveldan said:


> School me on "burn-in time" for caps, ive got fresh caps in a 100 watt JMP Marshall put in last friday.



Nothing to do but turn it on, turn it up, and PLAY! If the caps need to "burn-in" a bit to sound their best, then that will take care of itself. Most caps only need a few (5 or less) hours of burn-in time, if they need it at all. Enjoy! 

-Lane


----------



## charveldan

Lane Sparber said:


> Nothing to do but turn it on, turn it up, and PLAY! If the caps need to "burn-in" a bit to sound their best, then that will take care of itself. Most caps only need a few (5 or less) hours of burn-in time, if they need it at all. Enjoy!
> 
> -Lane


Thanks Lane, i turned that mother up to 4 today, AWESOME TONE!!!


----------



## MM54

Lane Sparber said:


> Matt - Rest assured you were NOT being ignored.  For my part, I just wanted to be sure and do some research before posting. To that end, I asked one of the senior engineers at work about this, and he said that ALL electrolytic capacitors are considered "dry" in engineer terminology, simply because the electrolyte is a moist paste and not PURE liquid which would require an air-tight seal (like a foil-in-oil cap). Any electrolytic cap made since the 50s is considered "dry," and older caps might be labeled as such to distinguish them from other types in the "good old days." To re-iterate, the aforementioned paste DOES contain moisture and WILL dry out, as Wilder, others and myself have been saying - it's just not LIQUID. I hope this makes sense to you.
> 
> -Lane



Aaah, okay. I was really perplexed about it since if they actually were dry they should have taken over by now .

Makes perfect sense, thanks!


----------



## RickyLee

Lane Sparber said:


> I wasn't speaking about a specific wiring scheme here, Marty. Ricky was asking a pointed question about certain voltages and what to do. I was answering his specific question.
> 
> Yes, you are correct in that in some Marshalls (with the first two filter caps in SERIES), the first filters are wired to be rated at 1000v, but that wasn't Ricky's question, I believe. He said AN amp...not a MARSHALL amp specifically. A standard, single 500v cap will work for both voltages he postulated above. If the filters in question are the MAIN filter caps, then yes, I should add that with those voltages it would be safest to wire two in series for the 1000v rating, although it would cut the capacitance in half, which is why higher value caps are sometimes used in these applications.
> 
> -Lane



I understand that the voltage rating of a 500V rated cap is good for the 450V, 475V application ect. I'll try to explain my question a bit better.




Lane Sparber said:


> NO - there is no "Memory" with filter caps. Now I see where you were coming from. Caps are NOT, and I repeat, NOT batteries!



LMFAO Thanks Lane for pointing that out for me. 

I had read that a capacitor that is ran at at a specific voltage - for example a 500V rated filter cap ran in a 400V application for a period of time (unknown) may suffer breakdown when changed to run at a higher voltage - let's say closer to it's rating voltage.

This is what I meant by "memory". And why I used the "changing out the power transformer" example. 

Yeah, I know, probably not a good word to use, but you get the idea.


----------



## Wilder Amplification

RickyLee said:


> I had read that a capacitor that is ran at at a specific voltage - for example a 500V rated filter cap ran in a 400V application for a period of time (unknown) may suffer breakdown when changed to run at a higher voltage - let's say closer to it's rating voltage.



As a cap ages and the dielectric dries up, obviously it wouldn't be able to handle its full voltage rating like it could when it was new. But this has nothing to do with "how long the cap has been ran at a given voltage" and everything to do with the actual age/remaining service life of the cap. In this instance if your caps are old enough to be that dried up you should be changing them out anyway.

My philosophy regarding how to tell cap age and wear...when in doubt, change 'em out.


----------



## jcmjmp

RickyLee said:


> I had read that a capacitor that is ran at at a specific voltage - for example a 500V rated filter cap ran in a 400V application for a period of time (unknown) may suffer breakdown when changed to run at a higher voltage - let's say closer to it's rating voltage.



Electrolytic capacitors are rated for a finite number of hours. They have a limited lifespan in which they operate at the spec'd value. Typically, capacitor lifespan goes from 5000 to 10'000 hours, depending on the quality and size of the capacitor. 

JJ's are particularly short life as they spec their replacement 500vdc 50/50 caps at 1000 hours with no additional details. Personally, as an electronics technologist, I would avoid parts for which I can not get full specs on and that have such a short spec'd lifespan compared to others.

F&T caps are spec'd out for much longer life i.e. anywhere from 80'000 hours to 5000 hours, depending on the operating conditions such as _*ripple current and ambient temperature.*_. In general, they are spec'd at 5000 hours at 85c. 

http://www.ftcap.de/downloads/elektrolyt/datenblaetter_2010/LF2010.pdf


----------



## Wilder Amplification

jcmjmp said:


> JJ's are particularly short life as they spec their replacement 500vdc 50/50 caps at 1000 hours with no additional details.



That's at maximum operating temperature of 70*C/158*F. None of our amps run in conditions anywhere near that. Of course F&T rates them 5000 @ 85*C/185*F which is in fact better, but due to the fact that none of our caps see anywhere near that temperature condition (unless you keep it stored in some hot ass garage or some shit like that) I'm sure you can get lots more hours out of both.

Of course then there's the "enclosed with hot valves" environment, in which I always advise to leave the back panel off.


----------



## Kunnz

Wilder Amplification said:


> That's at maximum operating temperature of 70*C/158*F. None of our amps run in conditions anywhere near that. Of course F&T rates them 5000 @ 85*C/185*F which is in fact better, but due to the fact that none of our caps see anywhere near that temperature condition (unless you keep it stored in some hot ass garage or some shit like that) I'm sure you can get lots more hours out of both.




I know this is a Marshall forum, but original VOX AC's should use those caps as they would easily get up to that temprature no sweat. The ventilation holes on those early combos sucked big time.


----------



## Lane Sparber

Kunnz said:


> I know this is a Marshall forum, but original VOX AC's should use those caps as they would easily get up to that temprature no sweat. The ventilation holes on those early combos sucked big time.



Yeah...they're kinda famous for that!

-Lane


----------



## RickyLee

OK fella's.

I have had about four sets of NEW filter caps sitting here for a few months now. YES, I have been putting it off for some time now!

I have too many amps that need the filter caps replaced. These are only JJ 50uF/50uF caps, but I got a good price on them. I was just getting ready to replace the three in my '83 2204. I was curious and started checking all these new JJ's with my capacitance meter. They are all balanced between the mult-sections/themselves, but I am getting a range from 52uF to 57uF.

My question is what position in my Marshall's circuit's would benefit from the higher value caps. For now I am replacing the filter caps in my '83 2204, '88 2205 and my '89 2550.

And as Jon pointed out on bringing up the voltage slowly to check for a bad cap, I do have a VARIAC. So would the powering up procedure with the new caps installed just be as simple as VERY SLOWLY bringing the amp's AC input power up from 0 to 120VAC?

Something else I thought of for people that live in the 120VAC part of the world that do not own a VARIAC, after installing new filter caps, could they power up there older Marshall's with the Voltage selector set to 240VAC first for just a few minutes to check for a bad NEW filter cap?


----------



## Lane Sparber

RickyLee said:


> My question is what position in my Marshall's circuit's would benefit from the higher value caps. For now I am replacing the filter caps in my '83 2204, '88 2205 and my '89 2550.
> 
> And as Jon pointed out on bringing up the voltage slowly to check for a bad cap, I do have a VARIAC. So would the powering up procedure with the new caps installed just be as simple as VERY SLOWLY bringing the amp's AC input power up from 0 to 120VAC?
> 
> Something else I thought of for people that live in the 120VAC part of the world that do not own a VARIAC, after installing new filter caps, could they power up there older Marshall's with the Voltage selector set to 240VAC first for just a few minutes to check for a bad NEW filter cap?



Ricky - that much variation (under 7 microfarads) will not make an appreciable difference in sound...just put 'em in ANY of your amps and you'll be fine. They are all within spec, and a few ufs here or there is nothing anyone would notice.

As to the Variac, I usually power the amp up at 40 volts, then leave it overnight to burn in. Then I raise it 10v an hour over an 8 hour day. You could, of course, do this over the course of an hour or two, I am just paranoid and methodical, so my OCD takes over. Also consider Jon's method above, which doesn't use a Variac.

Good luck, bro!

-Lane


----------



## RickyLee

Thanks Lane.

I replaced the filter caps in the '83 2204 last night. What I ended up doing was putting the high value 57uF plus pair farthest upstream - the parallel 50/50 coming out of the rectifier diodes. Then I just grabbed the other two cans for the next two spots. It actually matched quite close the values of the original 3 cans in there respective spots. I then did pretty much what you described, as before I went to bed, I powered the amp up with the VariAC, and slowly brought the the B+ up monitoring it with my meter on the first filter can - all tubes pulled out of the amp - and slowly brought the voltage up over close to an hour while I put everything away for the night. I let the amp run quite a bit at 490VDC and then right at 500VDC for a few minutes before powering down. But also did a quick swipe of the VariAC to go up to 510VDC then brought it back down LOL. 

Yeah, funny thing is, without the VariAC and having my tubes out of the amp, I would be going well over 500VDC as the VariAC was at 120VAC output to have my amp at just under 500VDC. My house voltage was over 125VAC last night! LOL 

I just got done ripping on the amp, and man I think it might be just a touch quieter. I just pulled my 2550 out and I am thinking about doing the cap job on her tonight . . .



That is only two of my amps that have newer filter caps now - shame on me. This 2204 and I did my '66 Bassman last year.


----------



## Lane Sparber

Good for you, man! It SHOULD be quieter, with all those new filters! 

Also, remember that your meter is testing those caps at 9v. Your amp pushes them at 500v. Therefore, as was said somewhere above in the wilds of this thread, any simple multimeter capacitance test is NOT accurate for our purposes here. What they do under the full voltage load may be QUITE different from what your meter tells you.

Cheers!

-Lane


----------



## RickyLee

RickyLee said:


> Thanks Lane.
> 
> I replaced the filter caps in the '83 2204 last night. What I ended up doing was putting the high value 57uF plus pair farthest upstream - the parallel 50/50 coming out of the rectifier diodes. Then I just grabbed the other two cans for the next two spots. It actually matched quite close the values of the original 3 cans in there respective spots. I then did pretty much what you described, as before I went to bed, I powered the amp up with the VariAC, and slowly brought the the B+ up monitoring it with my meter on the first filter can - all tubes pulled out of the amp - and slowly brought the voltage up over close to an hour while I put everything away for the night. I let the amp run quite a bit at 490VDC and then right at 500VDC for a few minutes before powering down. But also did a quick swipe of the VariAC to go up to 510VDC then brought it back down LOL.
> 
> Yeah, funny thing is, without the VariAC and having my tubes out of the amp, I would be going well over 500VDC as the VariAC was at 120VAC output to have my amp at just under 500VDC. My house voltage was over 125VAC last night! LOL
> 
> I just got done ripping on the amp, and man I think it might be just a touch quieter. I just pulled my 2550 out and I am thinking about doing the cap job on her tonight . . .
> 
> 
> 
> That is only two of my amps that have newer filter caps now - shame on me. This 2204 and I did my '66 Bassman last year.



Correction: Three amps with new caps - forgot about the '82 4010.


----------



## RickyLee

Lane Sparber said:


> Good for you, man! It SHOULD be quieter, with all those new filters!
> 
> Also, remember that your meter is testing those caps at 9v. Your amp pushes them at 500v. Therefore, as was said somewhere above in the wilds of this thread, any simple multimeter capacitance test is NOT accurate for our purposes here. What they do under the full voltage load may be QUITE different from what your meter tells you.
> 
> Cheers!
> 
> -Lane



I just measure with the capacitance meter for value. So that is really not all that correct for obtaining value? I realize you can not "test" them as you would say, using a meter. 

But then again, a meter would disclose a shorted cap?


----------



## Joey Voltage

jcmjmp said:


> and forming them or not would not have made a difference. You just proved that forming is useless for new caps. So many techs out there want to make things more complicated than they really are, and that bugs me.
> 
> Monitoring the caps for the first 5-6 hours is a good idea, but really, that's all you need to do, for new caps.



+1,000,000.


----------



## Joey Voltage

jcmjmp said:


> Electrolytic capacitors are rated for a finite number of hours. They have a limited lifespan in which they operate at the spec'd value. Typically, capacitor lifespan goes from 5000 to 10'000 hours, depending on the quality and size of the capacitor.
> 
> JJ's are particularly short life as they spec their replacement 500vdc 50/50 caps at 1000 hours with no additional details. Personally, as an electronics technologist, I would avoid parts for which I can not get full specs on and that have such a short spec'd lifespan compared to others.
> 
> F&T caps are spec'd out for much longer life i.e. anywhere from 80'000 hours to 5000 hours, depending on the operating conditions such as _*ripple current and ambient temperature.*_. In general, they are spec'd at 5000 hours at 85c.
> 
> http://www.ftcap.de/downloads/elektrolyt/datenblaetter_2010/LF2010.pdf



you just made me weep a little!


----------



## Joey Voltage

Wilder Amplification said:


> That's at maximum operating temperature of 70*C/158*F. None of our amps run in conditions anywhere near that. Of course F&T rates them 5000 @ 85*C/185*F which is in fact better, but due to the fact that none of our caps see anywhere near that temperature condition (unless you keep it stored in some hot ass garage or some shit like that) I'm sure you can get lots more hours out of both.
> 
> Of course then there's the "enclosed with hot valves" environment, in which I always advise to leave the back panel off.



Your neglecting Combo environment which is notoriously the worse for everything, you name it!


----------



## MartyStrat54

Maybe they should make an amp with a satellite cab for just the power tubes made out of a well vented, perforated metal housing. A two-piece if you will. Power supply and preamp plus the power tube section. Comes with a 25 foot cable so you can set the tube enclosure under the air conditioner.

:cool2:


----------



## MM54

I like it, Marty. You should design it 

On a more relevant note - Variac for bringing up an amp to power: 500W should be good, right? (And a 300W isn't enough, right?)


----------



## MartyStrat54

Did you see that new amp with the variac built into the amp? It is independent of the heater voltage, so you can adjust the B+ of the amp. I forgot who was making it. If I find it, I will post it up.

Found it. I have a mega search engine.











http://www.mojaveampworks.com/dirtyboy/DirtyBoy/Dirty_Boy.html


----------



## RickyLee

MartyStrat54 said:


> Did you see that new amp with the variac built into the amp? It is independent of the heater voltage, so you can adjust the B+ of the amp. I forgot who was making it. If I find it, I will post it up.
> 
> Found it. I have a mega search engine.
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> Dirty Boy





That is awesome for sure!!


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## MartyStrat54

Don't you wish that you had a job where all day long you tried out guitar amps, cabs and speakers? Tough life huh?


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## TwinACStacks

It's Mojave Ampworks from Victor Mason out in Cal. TOP-SHELF SHIT.

He runs The Plexi Palace Forum.

:cool2::cool2: TWIN


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## MartyStrat54

TwinACStacks said:


> It's Mojave Ampworks from Victor Mason out in Cal. TOP-SHELF SHIT.
> 
> He runs The Plexi Palace Forum.
> 
> :cool2::cool2: TWIN



Yeah I knew it was Mojave, but I didn't know who ran it. There's a lot of amp builders out there, isn't there?


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## hasic

Anything else to think of when using older amps except for re-capping and getting new tubes (and bias if needed)? Anything else that needs changing, cleaning or looking over?


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## Wilder Amplification

hasic said:


> Anything else to think of when using older amps except for re-capping and getting new tubes (and bias if needed)? Anything else that needs changing, cleaning or looking over?



Screen resistors as well as condition of the valve sockets. Bleeder resistors (if applicable) are also worth checking into for value drift and to make sure they're not blown.


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## hasic

How much is a reasonable price to pay for a trouble shoot, full re-cap and valve change?


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## Wycked Lester

Killer info guys....this is a subject i never was to clear on. Seems as if maybe, just maybe, there is a difference between right and wrong......

seriously though,....thanks for the info.....i feel like i know a lil about caps now.


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## Wilder Amplification

Wycked Lester said:


> Seems as if maybe, just maybe, there is a difference between right and wrong......



Get the vintage collectors involved on this thread and even that will be up for debate.


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## MartyStrat54

32 year old caps are just fine. They are OE with the amp. Why would I want to change out OE? When I plug it in it makes a ghastly noise. Sort of like Star Wars light sabers. Sssshhhhuuunnnkkk. Sssshhhhuuunnnkkk. Other than that it sounds like new. I'd like to run this baby on a power soak with full volume. People make such a big deal out of filter caps. Trust me, when they are getting ready to go, I'll be the first to know.

If your caps are only 20 years old, they're just getting broken in.





(I am not responsible for this information. Please ignore.)


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## Lane Sparber

MartyStrat54 said:


> 32 year old caps are just fine. They are OE with the amp. Why would I want to change out OE? When I plug it in it makes a ghastly noise. Sort of like Star Wars light sabers. Sssshhhhuuunnnkkk. Sssshhhhuuunnnkkk. Other than that it sounds like new. I'd like to run this baby on a power soak with full volume. People make such a big deal out of filter caps. Trust me, when they are getting ready to go, I'll be the first to know.
> 
> If your caps are only 20 years old, they're just getting broken in.
> 
> 
> 
> 
> 
> (I am not responsible for this information. Please ignore.)




[[[shudder]]] 

-Lane


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## MartyStrat54

The sad part of it is LANE is that some folks just like to see how long they can put something off. I'm a former Air Force COMM equipment guy. In the military, everything is documented. When I was in, we still used tubes in a lot of gear. We knew how many hours were on each tube. This applied to circuit boards as well. In the military, you have PMI's (Preventive Maintenance Inspection). In other words, you replaced parts before they could go bad. 

That's why when I bought my two old Marshall's, I didn't hesitate to tell Jon to change out the caps. I don't care if the amp still sounded good. That's not the point. They were old, original caps and I wanted them changed. I didn't want Jon to do the mod's and then four months later a cap went bad. It wasn't about whether or not I could have done it myself. I try to support those on this forum who share valuable information. I gladly paid Jon to do the work. After all, he was going to be inside of the amps anyway.

I enjoy your comments.


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## Lane Sparber

Thanks, Marty!  That means a lot. Really.

For the record, I agree wholeheartedly...I have had this battle with some customers before as to why these caps REALLY need replacing, and it's always a drag to go through it yet again. I have found - and the following little "trick" might help some of the other techs here get the job done - that I can pacify most collector types (as opposed to those who actually USE their amps regularly) by putting a little box in the head or combo cabinet with all of the old, worn parts I remove in it. This way, the owner will still have all of the original components when I'm done. Said box is accompanied by a STERN warning NOT to re-install the old, dead filter caps. It may not be perfect, but at least this method allows me to do my part to get those nice, great-sounding vintage amps working right again.

-Lane


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## eljeffebrown

Hey Jon (or anyone that wants to answer me for that matter) My 900 has never had new caps put in it as far as I know. it's a '92, do you think I need to get it done (or do it myself) and will it effect my tone on different caps I put in it? are they like tubes and do different brands matter?


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## MartyStrat54

Since you play a lot and at a louder volume, you are probably okay. Consistent amp use helps keep the filter caps rejuvenated. However, after 20 years, if it were mine, I'd change them out.


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## Lane Sparber

eljeffebrown said:


> Hey Jon (or anyone that wants to answer me for that matter) My 900 has never had new caps put in it as far as I know. it's a '92, do you think I need to get it done (or do it myself) and will it effect my tone on different caps I put in it? are they like tubes and do different brands matter?



EL JEFFE!!! I'm certainly not Jon, but I'll try my best! 

I would DEFINITELY suggest replacing the filter caps if they're original from '92. I guarantee you that they've dried out significantly from when they were new. They are not like tubes in that you won't notice a DRASTIC difference brand-to-brand as long as the caps are well-made. You WILL notice a difference between the new caps and the old ones you have in there now. To that end, Jon likes the F&T brand, and so do I. To buy, go here (I believe you need two of them):

Antique Electronic Supply

Once there, type this number into the product search window in the upper right hand corner: C-EC50-50-500FT. They're 9.95 pre tax and shipping.

Also, you might want to replace your bias filters as well. Order two of these:

TVA1406 Vishay/Sprague Aluminum Electrolytic Capacitors - Leaded They're $2.39 per.

There may be more electrolytic caps in your amp, depending on the model, but as your amp has been modded, there's no telling what's in there without pics of the insides. I'd humbly suggest taking it to a tech if you have never worked around high voltage circuits before or don't FULLY know what you're doing. If you do take it to someone, see what his price would be to do a FULL electrolytic re-cap. As to doing it yourself, when replacing filter caps, you're dealing with components that see the HIGHEST voltages in the amp, so beware and learn the proper precautions if you don't know them - for your own sake. 

-Lane


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## MartyStrat54

A beast of a thread. Worth going through for sure.


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## wkcchampion

I agree Marty, a lot to learn here.


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## diesect20022000

I'm so glad you put this up. I just got asked today aboutt his and i had to give the run down on it but, this is much more in depth and gives some info on the effects of not replacing them too which is great!


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## TwinACStacks

First thing I did when I traded the DSpLexi for my 2204 is order caps from AES. I went with the CE. Great caps I've used them before never had any problems with them, are the F&T that much better?

 TWIN


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## peterichardz

When I change caps, I date code them so I (or the next guy)knows how old they are.


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## lespaulboy

I've got two new F&T 500V 50uF/50uF caps coming today for my JCM900 and have a really basic question.

My old LCR caps have a ground or common terminal, a "yellow" terminal and a "red" terminal. I don't have the F&T's yet, so I don't know if they are color coded the same. At the end of the day (as long as you have correctly identified the ground / common terminal) does the color coding really matter... this is essentially two 50uf caps in one convenient package... correct?


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## Lane Sparber

The terminal by itself is negative...the two next to each other are positives. No color coding necessary, and, yes, these caps can be thought of as two separate caps with a common negative. When replacing, just follow the layout and orientation that's in there now and you should be golden.

For example...OLD caps (LCRs) BEFORE:






Finally, NEW caps (F&Ts) AFTER:








-Lane


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## lespaulboy

Awesome... thanks for the quick response!


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## Lane Sparber

Hey, folks!

I'm just popping by for a sec to update/revive this thread in order to clear up a couple of misconceptions I've seen floating around here recently. 

1. ALL electrolytic caps dry out over time. Yes, even the filter caps in solid state amps. After 10 years or so, they should at least be checked on a decent capacitor checker. If you don't have a cap checker, why not simply replace the caps as a precautionary measure at the very least? Especially on said solid state amps, the caps are VERY cheap to procure, so why not get those old caps out of there and sleep a bit easier at night? 

2. Almost all electrolytic caps are NOT sealed. This is _why_ they all dry out over time. It is true that if you use the amp often, it slows down the process considerably, but I assure you that they DO degrade, and often in this circumstance (frequent usage), their deterioration is so gradual that you don't really hear it happening...until a new set of caps is installed, that is. 

The techs (myself included) aren't just saying this for our health. I don't own stock in F & T, Sprague, Mallory or any of the others. We've just learned through research and hard-earned experience how the components we work with behave - it's our job! For the record, most of the data sheets for electrolytic caps list their life-cycle expectancies. What does that tell you? 

Cheers for now!

-Lane


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## Lowlife

Good thing to revive this thread, it really should be stickied. It's one of Wilders best in my opinion. I linked to it recently, because i haven't seen as good info elsewhere, took me a while to find it though.


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## FourT6and2

Sorry for the old-thread bump. But hey... I gots me some questions 

Building a 50-watt clone. Kind of a 2204 circuit. The first cap after the standby switch has a 220K bleeder from the first 50uF section to ground. I disconnect that bleeder from ground, then place a 100K/2W resistor in series with the other side's 50uF positive terminal to the SS rectifier? Then just power the amp up (no tubes)?


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## Exotic

why do people use photobuckets? photobuckets go bad? fuzzy blurry?


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## FourT6and2

Exotic said:


> why do people use photobuckets? photobuckets go bad? fuzzy blurry?



You bumped a 10-year-old thread to complain about Photobucket?


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## mickeydg5

*****E-x-o-t-i-c-!*****


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## Dogs of Doom

Exotic said:


> why do people use photobuckets? photobuckets go bad? fuzzy blurry?


photobucket used to be considered the internet standard for free image hosting. Then, 1 day, they decided to change, that they were going to charge for the image space, or, they would stop allowing images to be seen in forums.

Using their site for image hosting, for forum posts was their largest usage, so, they literally killed millions of threads, as far as being viable for illustration, or archive...


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## Exotic

omg that was so great i haven't laughed so hard in a very long time!
of course i did just wake up from a nap and i'm feeling a bit loopy


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## MickeyJ

yes I see the logic.
I'm going to change my 50y/o caps which work and make my amp sound non-bright and non- shitty, for shitty bright sounding modern caps!
All because the mains fuse may not blow?
No thanks, Ill keep my caps.
You left the bit out that says,' for some reason old filter caps sound great.'
When they balloon at the top, or when I hear ghosting, I'll change them.
Thanks for being so concerned about my amp.


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## MickeyJ

Lane Sparber said:


> For the record, most of the data sheets for electrolytic caps list their life-cycle expectancies. What does that tell you?



Judging by the amount of amps I've seen in the last year with original filter caps that are up to 55 years old, it tells me it's a pile of bullshit.

Judging by the amount of amps I've repaired in the last 20 years that distinctly lacked catastrophic secondary effects of a filter cap short, I submit a further bullshit call.

Why oh why would a manufacturer tell anyone that they need to give them more money every ten or fifteen years?

The original ones used in fender with paper around them, I agree. Cap cans, I don't agree unless there is leakage, blown out top or ghost notes.


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## paul-e-mann

MickeyJ said:


> yes I see the logic.
> I'm going to change my 50y/o caps which work and make my amp sound non-bright and non- shitty, for shitty bright sounding modern caps!
> All because the mains fuse may not blow?
> No thanks, Ill keep my caps.
> You left the bit out that says,' for some reason old filter caps sound great.'
> When they balloon at the top, or when I hear ghosting, I'll change them.
> Thanks for being so concerned about my amp.





MickeyJ said:


> Judging by the amount of amps I've seen in the last year with original filter caps that are up to 55 years old, it tells me it's a pile of bullshit.
> 
> Judging by the amount of amps I've repaired in the last 20 years that distinctly lacked catastrophic secondary effects of a filter cap short, I submit a further bullshit call.
> 
> Why oh why would a manufacturer tell anyone that they need to give them more money every ten or fifteen years?
> 
> The original ones used in fender with paper around them, I agree. Cap cans, I don't agree unless there is leakage, blown out top or ghost notes.



I'm no tech but I feel the same. My amp is almost 40 years old and looks and sounds great why change anything! My tech looked it over and said more or less the same, he did make me aware an old amp will need a cap job eventually and educated me on what to look for but did say everything looks fine so no hurry to change anything right now. So as a preventive measure I open my amp up about once a year and do a visual inspection and check the bias which never needs adjusting its rock solid.


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