Advice for removing PCB-mounted jacks? And is it important to charge new filter cans slowly?

Delicieuxz

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This is the first time I've done my own amp work. So far, on my 1985 JCM 800, I've replaced the filter cans, the bias trimpot (the original had been replaced with another kind using makeshift top-of-board soldering), converted the amp to 6550 spec, and removed the bias caps. Things have gone pretty well, so far. I want to replace the input jacks because they're dirty and make lots of noise, and since I have the PCB flipped, now's a good time to install ones that will hopefully last another several decades.

20221116_075248.jpg

The jacks have a couple of bent leads, to hold them in while being soldered. I want to straighten those leads so that I can pull the jacks out. They haven't budged with some slight force (maybe there's a faint trace of solder still holding them in place), and I'm cautious of using more force that might damage the solder pads. I don't see how I might be able to clip the leads to pull them out after removing the old jacks.

Is there a technique to do this safely?

Also, I don't have a variac. Is it important to form new filter cans the first time the amp is turned on with them installed? If so, maybe I'll need to take my amp to a tech for that, or buy something to do the job (any suggestions of what to get?).



Someone who previously owned this amp replaced the bias circuit components (maybe the person I bought it from had it at 6550 spec, and restored it before selling it to me... and now I'm setting it back to 6550 spec), and then replaced the original components by soldering them from the top of the PCB. They clipped R26 and R27 on one side, maybe accidentally while meaning to remove R24 and R25, the bias feed resistors, and then they resoldered them from the top. I have replacements and was going to replace them, but then wasn't going to replace them, to leave the originals in the amp (though, R26 doesn't appear to be the original brown one, but is red, like the replacements I have), but in the photo they look a bit gnarly and now I want to replace them.

D1 was also clipped from the top of the board, and then resoldered back into place. I wonder what they had done there. I have replacement diodes, too. But they don't have the same looking white stripe, so I might just leave that original one in there.

I've tightened the new Ars cans pretty well. I found the bracket clamps needed to be tightened more than they were previously in order for these Ars to not move / slip through brackets when pressed with a bit of force. I they won't be too tight, though I don't really know how to tell what's too tight.

20221116_075412.jpg 20221116_075425.jpg

Here's how the bias circuit looked before I did anything to it.

1985 2203 - bias circuit before restoration.jpg


BTW, I don't know if the weight of the old filter cans is relatable to the weight of the new ones, indicating how dried out they were or something, but some of the old cans weighed:

LCR cans: 73.9g, 79.43g
ITT can: 87.38g
unlabelled black can: 98.78g

And some of the new Ars cans weighed: 94.64g, 90.39g, 93.51g


Also, in a previous thread I made, I mentioned that one of this amp's old filter cans was emitting a large electrical spark at one of the bracket screws, and someone mentioned that it could be caused by the bracket clamp being too tight, or there being a burr on the bracket, and maybe cutting into the filter can. I don't know the mechanics of how it works. But the filter can I removed from that spot did have some of its outer plastic covering torn from the bracket, and there's a darkened spot that maybe indicates a burn where it might've been arcing. I wiped some debris from the bracket and put electrical tape around the base of the new Ars can I installed into that bracket.

20221116_084528.jpg 20221116_084539.jpg
 
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Pete Farrington

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I don't know the mechanics of how it works
2 of the 4 cans have their negative terminal elevated to half the HT voltage.
Although there may not be a direct connection internally between the can and negative terminal, in use the can tends to assume the same voltage as the negative terminal.
Those caps need a tough, additional layer of insulation between their can and the clamp.
I recall this was explained in the relevant thread?

Also, I don't have a variac. Is it important to form new filter cans the first time the amp is turned on with them installed?
It is extremely beneficial to use a light bulb limiter between the mains outlet and the amp after significant repairs have been done.
Additionally, the use of a low power bulb also may help with cap forming. All valves should be removed for that.
 
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Gene Ballzz

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Removing those jacks is kind of a tricky technique to explain with the typed word, but I'll try.
> Use a small screwdriver, or similar, to bend those tabs straight. Quite often the process of straightening them will "breaK' that last bit of solder holding them. If not, carefully de-solder a bit more and try wiggling that tab back and forth again, until it breaks free. A good solder sucker and careful, well practiced use of de-soldering wick can be your friends here!
> Use the same process for the tabs that are already straight.
> Once all tabs are free, simply wiggle/pull the jack out of position.

I applaud you for the ambition to do this work for yourself, with at least a couple caveats:
>> FIRST & FOREMOST: Make sure that you understand how to properly discharge all voltages in the amp and how to test that the task has been properly accomplished!
NEXT>
Understand that inexperienced work on a printed circuit board may well cause some damage. Utmost care is needed to avoid this, but there are worse things in life than needing to bypass a damaged solder pad or trace, neatly, with a suitable wire!
Be careful & Enjoy!
Gene
 

lastgen

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You could buy a used de-soldering station that heats the solder and uses a vacuum to safely remove it from the board. You can find them on ebay, made by Pace and others.
 

Matthews Guitars

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I deal with troublesome jack removals this way:

Use solder braid or a solder sucker and a good soldering iron (45 to 75 watt range) to pull all the solder out of the joints.
Straighten the leads so the jack can be removed easily. If you can remove the jack without much force, good. If not, go to stage 2.

Stage 2: Using sharp diagonal cutters, trim back as much of the desoldered leads as you can, close to the PC board without damaging it.
Now, apply a BIG blob of fresh solder to all the jack connections. With a cable inserted in the jack, heat up all the connections one at a time until the solder melts, and gently use the cable end to pry the jack away from the board, one small step and one solder joint at a time. Walk it around as you gently pry the jack away from the board. This will usually free the jack in a few trips around.

Gently is the important word here. You don't want to damage the board or circuit traces.
 

Delicieuxz

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I got the jacks off without damaging the solder pads using desolder braid, a few differently-sized screwdrivers, a couple now-scratched-up fingernails, and patience. And when I installed the new jacks, I did not bend the leads. So, should they need replacing in another few decades, whoever does it will have no trouble with it.

20221116_221222.jpg 20221116_223134.jpg

I also went ahead with replacing D1, R26, R27, to make things look clean.

20221116_224520.jpg

I also used Simichrome polish on a couple of small rust spots.

20221116_224137.jpg 20221116_223538.jpg 20221116_223836.jpg

I, unfortunately, made some scratches on the back of the chassis' gold cover, where I attached alligator clips to ground for discharging the filter caps and taking measurements. I'm glad I didn't attach them to the front of the chassis. In the future, I will clip them to the side metal panels, that the headshell / chassis screws fasten into.

20221116_231328.jpg

And I gave the speaker jacks red nuts, for easy identification and pizazz.

20221116_231817.jpg

I think I'm all done on the internal work for this amp, other than installing the bias caps, which I'm awaiting the arrival of in the mail, and then reattach some wires I removed to be able to flip the PCB over.



2 of the 4 cans have their negative terminal elevated to half the HT voltage.
Although there may not be a direct connection internally between the can and negative terminal, in use the can tends to assume the same voltage as the negative terminal.
Those caps need a tough, additional layer of insulation between their can and the clamp.
I recall this was explained in the relevant thread?


It is extremely beneficial to use a light bulb limiter between the mains outlet and the amp after significant repairs have been done.
Additionally, the use of a low power bulb also may help with cap forming. All valves should be removed for that.
I guess I don't have the electrical knowledge to have understood it. I've put electrical tape around only the one can that the spark was emanating from. Which of those four cans is the other one that can use additional insulation via electrical tape wrapping?
 
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Spanngitter

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You did a quite decent job on this JCM800.
In general it is adisable that when replacing components on Marshalls you snip them off on the component side, bend the remaining leads straight and then desolder them to the solder side using solder pump/wick or a Desoldering Station. Also ensure that you don't overheat the traces as they will then suddenly lift off the carrier material...
On a side note I am a bit surprised to see one of the black 50uf/50uf 500V caps installed in a pre '82 JCM800 as so far I only found them in vertical Input Models built between ~late 79 till 82. So either this one was replaced before or they still had some of these caps flying around whilst normally all amps from 83 on I had on my bench so far had been equipped with LCRs....
 
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acromarmot

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This is the first time I've done my own amp work. So far, on my 1985 JCM 800, I've replaced the filter cans, the bias trimpot (the original had been replaced with another kind using makeshift top-of-board soldering), converted the amp to 6550 spec, and removed the bias caps. Things have gone pretty well, so far. I want to replace the input jacks because they're dirty and make lots of noise, and since I have the PCB flipped, now's a good time to install ones that will hopefully last another several decades.

View attachment 119336

The jacks have a couple of bent leads, to hold them in while being soldered. I want to straighten those leads so that I can pull the jacks out. They haven't budged with some slight force (maybe there's a faint trace of solder still holding them in place), and I'm cautious of using more force that might damage the solder pads. I don't see how I might be able to clip the leads to pull them out after removing the old jacks.

Is there a technique to do this safely?

Also, I don't have a variac. Is it important to form new filter cans the first time the amp is turned on with them installed? If so, maybe I'll need to take my amp to a tech for that, or buy something to do the job (any suggestions of what to get?).



Someone who previously owned this amp replaced the bias circuit components (maybe the person I bought it from had it at 6550 spec, and restored it before selling it to me... and now I'm setting it back to 6550 spec), and then replaced the original components by soldering them from the top of the PCB. They clipped R26 and R27 on one side, maybe accidentally while meaning to remove R24 and R25, the bias feed resistors, and then they resoldered them from the top. I have replacements and was going to replace them, but then wasn't going to replace them, to leave the originals in the amp (though, R26 doesn't appear to be the original brown one, but is red, like the replacements I have), but in the photo they look a bit gnarly and now I want to replace them.

D1 was also clipped from the top of the board, and then resoldered back into place. I wonder what they had done there. I have replacement diodes, too. But they don't have the same looking white stripe, so I might just leave that original one in there.

I've tightened the new Ars cans pretty well. I found the bracket clamps needed to be tightened more than they were previously in order for these Ars to not move / slip through brackets when pressed with a bit of force. I they won't be too tight, though I don't really know how to tell what's too tight.

View attachment 119337 View attachment 119338

Here's how the bias circuit looked before I did anything to it.

View attachment 119339


BTW, I don't know if the weight of the old filter cans is relatable to the weight of the new ones, indicating how dried out they were or something, but some of the old cans weighed:

LCR cans: 73.9g, 79.43g
ITT can: 87.38g
unlabelled black can: 98.78g

And some of the new Ars cans weighed: 94.64g, 90.39g, 93.51g


Also, in a previous thread I made, I mentioned that one of this amp's old filter cans was emitting a large electrical spark at one of the bracket screws, and someone mentioned that it could be caused by the bracket clamp being too tight, or there being a burr on the bracket, and maybe cutting into the filter can. I don't know the mechanics of how it works. But the filter can I removed from that spot did have some of its outer plastic covering torn from the bracket, and there's a darkened spot that maybe indicates a burn where it might've been arcing. I wiped some debris from the bracket and put electrical tape around the base of the new Ars can I installed into that bracket.

View attachment 119340 View attachment 119341
Hi,

regarding the sockets (or any electronic component for that matter):
- mechanical force on cold solder or pcb pads is not good.

We do it this way:
-if possible cut the socket from the component side of the pcb using a flat sharp electronic side cutter. Cut each leg individually. Helps to get space by carefully breaking the socket housing. Again: you don't want to have mechanical stress on the solder pads or through contacts.
Once the socket is gone, apply solder to the pad and heat it up. Take a pair of pincetts to pull the remaining socket leg.
Clean the pad completely with desoldering wire.

- if above procedure isn't possible, apply solder to the pad. Heat it up and use tiny screwdriver to bend the legs straight (while you're gently keeping the solder liquid)
Heat all the pads in turns and each time pull the socket a bit until it's out.
After that, clean pads with desoldering wire.

Side note: during my vocational training and later on the job we tried also with desoldering units (Weller and alike) but we never got good results, especially not on two or multi layer pcbs. YMMV

Good luck :)
 

acromarmot

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You did a quite decent job on this JCM800.
In general it is adisable that when replacing components on Marshalls you snipe them off on the component side, bend the remaining leads straight and then desolder them to the solder side using solder pump/wick or a Desoldering Station. Also ensure that you don't overheat the traces as they will then suddenly lift off the carrier material...
On a side note I am a bit surprised to see one of the black 50uf/50uf 500V caps installed in a pre '82 JCM800 as so far I only found them in vertical Input Models built between ~late 79 till 82. So either this one was replaced before or they still had some of these caps flying around whilst normally all amps from 83 on I had on my bench so far had been equipped with LCRs....
Sorry, didn't see Spanngitter already covered this :facepalm:
 

Delicieuxz

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The bias caps I had been waiting for arrived today. They took a while, and the tracking showed they went back and forth between the same two cities a couple of times, so I guess there was a mail error.

But I've installed them now, and reconnected the wires I had removed to be able to flip the PCB over. The amp should now be ready to be turned on. Maybe.

When I was reconnecting the grounding wires next to a couple of filter cans, I clumsily melted some of the filter cans' plastic insulation. So, now I'm wondering: how bad are these melted spots, and should I do something about it before I power on the amp?


First one:

20221129_205456.jpg 20221129_205507.jpg

Second one:

20221129_212415.jpg 20221129_212426.jpg
 

Matthews Guitars

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Gotta be honest, that's some pretty awful soldering work there on the cap wires. But it should work. Definitely take a minute to clean up any splashed solder balls and crusts in the area.

I can't know why your soldering on the cap wires is so...not great...but yet it's fine on the PC board.

Whatever it is, you should have someone give you a soldering class. Youtube has videos that will help you.

Good soldering starts with the proper amount of heat and properly cleaned parts to be connected.
 

Delicieuxz

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I put an extra layer of electric tape around the can in the "second one" photos, and tested the amp out. It seems to work just fine! I dialed in a rough bias, but found that the "matched" KT88 tubes I got for this amp are far from it, sitting right now with mA of 31, 33, 38, 36. Oh well, I'm glad the work I did was successful.

Gotta be honest, that's some pretty awful soldering work there on the cap wires. But it should work. Definitely take a minute to clean up any splashed solder balls and crusts in the area.

I can't know why your soldering on the cap wires is so...not great...but yet it's fine on the PC board.

Whatever it is, you should have someone give you a soldering class. Youtube has videos that will help you.

Good soldering starts with the proper amount of heat and properly cleaned parts to be connected.
The black wires with solder balls... I couldn't get the old leads that already had solder on them through the holes, and I didn't want to strip the wires more to create clean lead-ends. So, I soldered them next to the grounding tags like so. But, yeah, I'll aim to make things look nicer in the future.

For heat, I keep my soldering iron at 375C.
 

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Delicieuxz

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Have to agree with @Matthews Guitars, that soldering job needs work.

First off, I don't think your soldering iron is hot enough. Are you using one of those crappy 12 dollar home depot irons?

And also, what kind of solder are you using? I hope you are using lead solder...
The soldering iron I bought some years ago from someone locally. It's 60 watts and has a temperature control that lets it be set from 200C up to 450C. I've built a bunch of pedals before, and after burning a solder pad or two, I've generally keep it at 375C and haven't encountered an issue. But since the cans don't have solder pads that might lift, I could be more aggressive with the heat. I might redo some of those connections on the cans at a higher temperature and see how it turns out. BTW, the camera flash makes those connections appear a lot grittier than they do by eyesight. But perhaps shouldn't look that way even with the flash?

I'm using 60/40 lead solder.
 

Naldo

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My family was in the electronics repair business for many years. We used to repair everything from tube radios & amplifiers, to televisions & VCRs, to computers & printers, all at the component level. Two small points I would add which I think might be helpful for the OP and for anyone else reading this post:

1. ALWAYS USE only HIGH-QUALITY SOLDER. There is a LOT of VERY CRAPPY solder being sold out there. Don't buy it. All solder is NOT the same, and here is an instance where quality DEFINITELY makes a big difference. Even if it works & lasts, crappy solder is much more difficult to work with and makes a mess. The solder I use & strongly recommend is Kester #24-6040-0039. It heats & flows really nicely, and makes for a very clean & neat soldering job. Kester is THE solder brand for electronics professionals. MUCH easier & nicer to work with.

2. There is a bit of an art to de-soldering. I have seen guys burn up a PC board trying to de-solder components. . . not to mention ripping traces and breaking pieces of components when trying to pry them off the board while heating the crap out of it. Because liquified hot solder makes the most contact with a component's legs and with the solder pads on the board, it is by far the best heat conductor from your solder iron. Most people who are highly skilled with a solder iron will add a bit of solder to the iron tip just before they even touch the part they want to de-solder, because that liquified hot solder will transfer the heat most quickly & efficiently. After your de-soldering point is sufficiently heated, you need to remove the solder which is holding your component. Although solder wick (braided copper) is very useful for wicking up solder from more exposed surfaces, it is sometimes insufficient to soak out the solder from through-PCB connections. When de-soldering, I always use a good solder-sucker instead. After removing the component, I may go back and clean things up if needed with solder-wick, but for de-soldering components, a good hand held, spring-loaded, plastic solder-sucker is hard to beat. They are inexpensive and effective. If you suck out the solder, but the leg is still attached, then you just re-solder the leg back in (add solder) and then suck it out all over again. Repeat as necessary. I know that it sounds counter-intuitive to add solder to something you are trying to de-solder, but it works. Otherwise, you see inexperienced people burning up the PC board, trying like hell to melt a bit of inaccessible solder, and then just prying it off by force anyway.
 

Matthews Guitars

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I use only top brand name solders. Kester and Multicore. I prefer Multicore. It's AWESOME.

Understand, I approach soldering and electronics assembly and repair from a professional, not a hobbyist, point of view, so my views may be viewed as rather extreme, or you may see me as the electronics geek form of an elitist pig, or something. But I REALLY recommend that if you are going to be doing any but the most casual type of soldering, connecting two wires once every few months, then it's absolutely well worth it to invest in a GOOD iron. My no. 1 all-around recommendation for anybody who'll be soldering regularly is a genuine Hakko FX-951 bought from an authorized Hakko dealer, and NOT from any other source, because the Chinese have made a lot of cheap knockoff copies of this station and they LOOK very similar but their quality and performance is very bad.

List price is about $270 these days. Totally worth it. I have two of them and a big assortment of tips.


1669847412520.png




Above that level, for the guy who's truly serious about soldering and needs elite class equipment, the answer there is JBC.
I'm very fortunate to have access to late model JBC equipment that I can basically use for as long as I want, for free, and as good as the Hakko stuff is, which I WILL say is BETTER than your common temperature controlled classic Weller station by a good margin, the JBC stuff is just on another level entirely, literally in a class by itself BUT it's expensive. I keep two JBC stations for personal use, and they have more or less replaced the Hakkos.

I got to play with one of these for a while recently, and for working on surface mount boards and fine pitch components, I can't imagine a better setup. But it's about 1400 dollars....

What's the big difference between gear like this and your 50 dollar iron? In a word, it's heat control. The right amount of heat, when you need it. With reserve power to keep temperatures up when soldering something with a lot of thermal mass. FAST ramp-up to temperature, and stability when at temperature.

1669847722371.png
 

Gunner64

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Absolutely on the cheap solder. Shitty solder looks just like the pics above. The main problem is the cheap crap is so dirty you can't keep things clean. Your tip will funk up in no time, leading to hammered shit looking, compromised joints. Get good 60/40.

I use Kester, or the Radio Shack 60/40, which I think is Kester in disguise.

And I agree, A good solder/desolder station is a must!

Mine is a Hakko FM 202, with a Hakko FM 2024 desolder box and gun. Almost effortless. Heats to temp in seconds. 20221118_102436~2.jpg
 


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