# Longest Metro Plexi 50 Build



## Exojam

Well I have decided to start getting this build on the way. Have not made to much progress but I am in no rush at all.

I am using Marstan PT, OT and choke.

Picked up all the parts from Valvestrom.

More pics when I make more progress.

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## ampmadscientist

Exojam said:


> Well I have decided to start getting this build on the way. Have not made to much progress but I am in no rush at all.
> 
> I am using Marstan PT, OT and choke.
> 
> Picked up all the parts from Valvestrom.
> 
> More pics when I make more progress.
> 
> View media item 10093
> View media item 10092



Longest Metro Plexi 50 Build

That's a Bold Claim.
Just how long is it?


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## Exojam

Well with being in the process of a 19 month period to stay alive and now recover, trying to fix this Blackstar HT100 Head, practice my guitar and have a family. 

It will be a long build time


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## Exojam

Plus a good 9”’s!


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## Exojam

Heater wires all installed.

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## Big Mike

Heaters look pretty good, those are annoying.


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## Exojam

Thank you. Yeah, getting my chubby fingers in there to twist them was not the most fun thing.


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## Gunner64

Try tying one end of the pair to something stationary and put the other end in a cordless drill and twist away..dont go too far though..no need to twist in the amp..I pre-twist.


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## Exojam

Gunner,

I had seen that done before but I was not sure if I could use that method due to one end of the wires being of different length. Plus, I was not sure how much extra I would have but I will pre twist going forward.

Thanks for the input.


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## neikeel

The drill method works well but you do lose a bit of wire when you untwist enough to solder the ends in. 
Personally I don’t leave those long black loops in the preamp pin 9 wires.


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## ampmadscientist

Exojam said:


> Well with being in the process of a 19 month period to stay alive and now recover, trying to fix this Blackstar HT100 Head, practice my guitar and have a family.
> 
> It will be a long build time



That is long.
Perhaps the longest.


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## Exojam

neikeel said:


> The drill method works well but you do lose a bit of wire when you untwist enough to solder the ends in.
> Personally I don’t leave those long black loops in the preamp pin 9 wires.



What is the purpose of those loops if any (as I cannot see any benefit)? I just tried to make it like the instructions showed.


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## Exojam

ampmadscientist said:


> That is long.



The 19 months was hardest shit I have ever been through, and being a para for going on 20 years, I have been through some tough goes of it.


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## neikeel

Don’t know really I think idea was to approach the sockets at 90 degrees and ensure the other wires crossed these at 90degrees to.


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## ampmadscientist

neikeel said:


> Don’t know really I think idea was to approach the sockets at 90 degrees and ensure the other wires crossed these at 90degrees to.


If the signal wires are parallel to heater wires, you get a lot of hum.
If the signal wires are 90 degrees, you will pick up a lot less hum.

But it actually helps to get the heater wires vertical straight up from the socket too. That's how Fender does the filaments.
In this case heaters vertical and signal down near the chassis, the noise is reduced more.


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## neikeel

ampmadscientist said:


> If the signal wires are parallel to heater wires, you get a lot of hum.
> If the signal wires are 90 degrees, you will pick up a lot less hum.
> 
> But it actually helps to get the heater wires vertical straight up from the socket too. That's how Fender does the filaments.
> In this case heaters vertical and signal down near the chassis, the noise is reduced more.



Yes that is what I said. 
What I am not sure is why such big loops as I think that they are more likely to encroach on grid wires and cause noise.


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## Exojam

I told you guys it would be a long build.

I had to put it down for awhile while I try and finish fixing (I hope) this Blackstar HT100 I had purchased that I purchased knowing it did not work. Getting close to wrapping it up and will see if I got it or not. Than back to the Plexi.

I received the below wiring change (from the book) from the gentleman from Valvestrom.

Notes:

AC Line in - 

L (Hot) black wire to tip of mains fuse holder, sleeve of fuseholder to one side of power switch, other side of switch to brown (120) PT wire AND to one side of 120vac lamp

N (Neutral) white wire to H on PT, H also goes to other side of lamp via a white wire.

G to new, dedicated ground lug on end of chassis

The other PT AC wires (1,3,4,5) should have individually heatshrinked tip then be bundled out of the way.


PT Secondaries – To rectifier as indicated above.

I use D & F initially, these will yield voltages that are more friendly to modern power tubes, C & G are higher voltage, can easily more the wires if desired.


Heaters – to v5 as indicated above. J to ground lug


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## Exojam

Well I had to jump ahead of the instruction manual and hooked up the below wiring, baby steps.

Next is is to drill a hole in the chassis for a ground lug for “G” of the input power.

AC Line in - 

L (Hot) black wire to tip of mains fuse holder, sleeve of fuseholder to one side of power switch, other side of switch to brown (120) PT wire AND to one side of 120vac lamp

N (Neutral) white wire to H on PT, H also goes to other side of lamp via a white wire.


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## neikeel

Normally you bring the ac wires in the corner of the chassis and then up from the front to the PT (ie dont have that white neutral wire there, run it under the rectifier in that loom bundle then up to the lug. You will shrtly take another white wire from the HT lug to the bias feed on the board


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## Exojam

No problem, that will just take a few minutes to unsolder the connections and run another piece of wire. Thanks.


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## Exojam

neikeel said:


> Normally you bring the ac wires in the corner of the chassis and then up from the front to the PT (ie dont have that white neutral wire there, run it under the rectifier in that loom bundle then up to the lug. You will shrtly take another white wire from the HT lug to the bias feed on the board



Just a slight comment, clarification. The small white wire coming from the PT going to the indicator lamp will be able to stay since it is so short and really cannot be routed any other way correct?

Maybe just tucked away a bit better.


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## neikeel

Just flick it down to run as low on the chassis as possible


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## Exojam

Sounds good. Thank you.


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## Exojam

I think this is what you were looking for, best I can run it.

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## Exojam

Well I am getting some more done. Installed pots, speaker jacks, input jacks, impedance selector and maybe some other things.

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## neikeel

Keep going!
Can you route your red/black heater wires from the PT to V5 in the far corner of the chassis (hard against the side and back).


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## Exojam

Neikeel,

I can check and see if there is enough slack to reroute them, otherwise I might be able to use some of my own red-black wire to do it.

I completely messed up and did not catch I ordered and installed a voltage selector switch instead of an impendeance selector switch. I ordered the correct one yesterday and will install it when it arrives, talk about a face palm moment when I saw that!


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## Exojam

Are you talking more in the lines of the yellow or red line for the rerouting of the heater wires? Thanks.

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## neikeel

You can do both but I would go for the red line, that keeps all AC well away from any signal wires.


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## Exojam

OK, sounds good but that one area is going to be very crowded but I can make it happen.

Thanks again.


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## Exojam

Put the proper impedance switch in and reran the wiring. Hopefully that is good enough.

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## Exojam

Buss wire done. Now to start cutting the wires for board wiring.

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## Exojam

One side of the board wiring done.

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## Exojam

Well I am at the point were I dropped the board into the chassis and am starting to wire everything up.

one thing I do not like are the instructions on wiring the inputs.

On page 32 of the instruction manual, the wire closet to the edge of the board goes to the bottom terminal of the top input. The wire to the right of that wire goes to the top terminal of the same input. 

On page 22 of the instruction manual. It appears to show that the wire closest to the edge of the board goes to the top terminal of the input, and the wire next to it goes to the bottom terminal of the same input.

I am not sure if it matters in the end but I wired it according to the picture on page 22.

Page 22 of manual


Page 32 of manual


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## neikeel

That looks correct.


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## Exojam

Thank you.


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## Exojam

Little more progress made. I have half the board wired up (mostly) and will keep going when I have some more time.

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## Exojam

Time to start adding the components.

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## Exojam

A little bit more progress.


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## Exojam

And a little more.


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## neikeel

Nearly there!!


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## Exojam

If can get to the point where I do not need more surgeries and get off the antibiotics I may make some real progress.

How does she look so far?


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## Exojam

Well it is all put together. In some ways I am happy with how it came out but the MAJOR OCM in me will see a wire that is not perfect and it will bother me.

In the next few days it will go through it voltage checks without and than with the tubes. I will start it with JJ’s even though I just do not like them. Once I am satisfied with how that goes I will put my NOS tubes in. Not sure what will go in the preamp section but I have some (supposed to be) very nice Mullard matching power tubes.

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## Exojam

Built a little stand so I can my measurements with.

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## Chris-in-LA

The black wire that you used on top of the board, is that shielded?


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## Exojam

Chris-in-LA said:


> The black wire that you used on top of the board, is that shielded?


Yes it is.


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## neikeel

I think he is confused. It is insulated bus wire. It does not need (or appear to be shielded). The Metro/Valvestorm kit comes with correct bus wire and insulation. I would always encourage builders new to this type of build to do that and ideally use perf'd board to loop the correctly coloured wires through the holes to the turrets to help with trouble shooting if there are problems later.


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## Exojam

Sorry for the wrong information.

I definitely wish I would have ran the wires all the way through the turrets when I wired it up.


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## Chris-in-LA

Exojam said:


> Sorry for the wrong information.
> 
> I definitely wish I would have ran the wires all the way through the turrets when I wired it up.


Run them from the bottom to the top of the turret? On my last build I just wrapped them around the base of the turret. I see that Metro has you fold the end of the wire and insert it into the bottom, is that what you did?


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## Exojam

For those black wires and two others I wrapped them around the turrets.

All other wires I installed as directed in the manual.


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## Chris-in-LA

That build is very clean with the wires run from the bottom. I’m going to try that on my Metro 50 Plexi/2204 conversion project.


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## Exojam

Thank you.

I have to give Neikeel a ton of credit for always being there to offer his help and constructive advice. He is one very intelligent person when it comes to amps.


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## Exojam

Well I ran into a problem when I started on the voltage checks, the 3 amp fuse was blowing.

With the help of a few folks they noticed I wired the voltage regulator incorrectly. What a dumb as move on my part and as slow as go I am not sure how in the heck I pulled that one off but I did.

Anyway, just waiting for some more fuses and I will rewire the voltage regulator and see what I get.


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## Chris-in-LA

Voltage regulator? Is that the bridge rectifier?


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## Chris-in-LA

Oh yeah, I see the problem but I wouldn’t have noticed it without you saying it, the wiring to the rectifier was wrong.


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## Exojam

Yeah I meant to say rectifier and not regulator.


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## Chris-in-LA

Exojam said:


> Yeah I meant to say rectifier and not regulator.


I’m getting ready to do a Metro kit with that same rectifier, did you get yours all sorted out yet?


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## neikeel

The rectifier is marked with ~ on two pins, +ve on another and -be on the fourth. 
The kit uses single pole switches so the PT is hooked directly to the ~ terminals and the + to the standby switch which then goes to the mains cans and choke etc. The -ve has no connection on a 50w. I personally prefer to use two double pole switches for mains (to switch live and neutral synchronously) and to switch the ac from the PT to the diode block But the kit arrangement is ok.


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## Exojam

Chris-in-LA said:


> I’m getting ready to do a Metro kit with that same rectifier, did you get yours all sorted out yet?



I just got my fuses in yesterday so after a bit of cleaning of my van that was totaled (getting all the stereo stuff out) I will be able to rewire and test a bit today (hopefully).

And if you can do your kit like Neikeel mentions, I would. Unfortunately I reached out to him for help after I already purchased my parts.


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## Exojam

This should work a lot better. While I was in there I redid some wiring I was not happy with.

I will fire her up after I run some errands.

I am also thinking I may just use the head with the little stand I made until I can make the proper one for it.

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## mickeydg5

Every time I see this thread I am waiting to see a picture of a 12 foot long Plexi head.


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## Exojam

I will have to find a way to stretch the head to make it longer (that just sounds so bad).


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## mickeydg5

Yes 12 foot long with 8 4x12's under it.


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## Exojam

Well she fired up just fine and the voltage reading are below. The bias is setting around 39mv on V5 and 37mv on V4 with a reading of 450vdc on the HT fuse. This with the bias pot full clockwise for full current. I will wait for everything to settle down before doing the bias again.

It appears as voltages are moving around a bit as I would expect. I am just going to leave on and connected to the speaker cab (Marshall MG412A).

The only thing strange to me right know is when the instructions stated to turn up volume one until you hear the normal speaker hiss which I never heard. The head and cab are both 8 ohms.

Later tonight or tomorrow I will bring the head into the house and change out these JJ tubes with the NOS tubes I have for this head and check out the bias and see if I get any output with a guitar hooked up. This is because I never got my hiss according to the manual.


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## Exojam

Well I am going to leave it up in standby over night and check things agains.

Due to the weather coming in I decided to run a guitar out to the shed to see if I would get any output. Much to my disappointment I am getting sound from all four inputs but the output is really not there. My little Blackstar 3 watt amp sounds louder than this one.

I did not like the look of V2’s heaters so when my wife brought it in for me I put a 12AX7A GE NOS in that slot and the heaters did come to life but not the sound, this time hooked up to my 8 ohm Mesa.

I am sure it should be pretty simple so I will break out the schematic tomorrow and grab som more readings, redo the bias and go from there.

I do believe this amp should be able to reach the neighbors house with the volume on it and the guitar at 11, but it ain’t happening right now.


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## Chris-in-LA

Exojam said:


> Well I am going to leave it up in standby over night and check things agains.
> 
> Due to the weather coming in I decided to run a guitar out to the shed to see if I would get any output. Much to my disappointment I am getting sound from all four inputs but the output is really not there. My little Blackstar 3 watt amp sounds louder than this one.
> 
> I did not like the look of V2’s heaters so when my wife brought it in for me I put a 12AX7A GE NOS in that slot and the heaters did come to life but not the sound, this time hooked up to my 8 ohm Mesa.
> 
> I am sure it should be pretty simple so I will break out the schematic tomorrow and grab som more readings, redo the bias and go from there.
> 
> I do believe this amp should be able to reach the neighbors house with the volume on it and the guitar at 11, but it ain’t happening right now.


Hell, my Champ reaches the neighbors. A 50 watt Plexi should be so loud that it would cause pain, at least my 50 watters are that loud.


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## neikeel

Well done that you have sound and all the voltages look correct.

Classic error on these is that you put a 470k resistor in the PI on the cathode instead of 470R, although looking at your board pics it looks correct.

Post some pics of the whole amp of inputs, board and sockets.

Looking over your pics I wonder if you may have a dry joint on one or more of your turrets? Most likely a grid wire. I can't see really good pics of your PI ground wire (from the presence pot) and the ground wire on the output jacks.

Check the filter caps are empty and reflow all the turrets properly so each one is shiny bright and full of solder.


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## Exojam

Neikeel,

I can get some pictures today but unfortunately with the snow and ice we got last night I cannot get my wheelchair through it to reach my tools. I will see if the better half can get them for me tomorrow.

I suspect something silly I missed or as you put out there a solder joint. To be honest there where times I was nervous about how much solder to flow when putting the components in since I was worried about the wire on the back side coming out, but we shall see.

Thank you again.


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## Exojam

Neikeel,

I went through all wires and components and did a light tug test on them and found three wires that need to be resoldered. They are circled below from a page in the manual but I believe you can tell which ones they are.

I also found an issue with one of inputs 2 wiring where it broke off underneath the board. I also feel I have the inputs wired incorrectly as shown in my terrible painting below.

Below is a link to 14 pictures I took all around the amp for you t take a look at. If You notice any black on top of the turrets that is from where I use a Sharpie to mark where I should bend the leg of the component that was to be soldered into the turret.

https://www.dropbox.com/sh/axn4iuo7ab5td07/AAATw8j5EAHUQ18GhJr2it2ea?dl=0




The painting is how I have them wired.


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## mickeydg5

The 470R show in the pictures.


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## Exojam

Yeah he is in there.

I am going to probably need to swap out the 47K bias resistor with something lower to help with the biasing though.


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## Exojam

I know it is being discussed in Chris's 2204 build about having the 47K resistor tied to the 8 ohm tap of the impedance selector but I wanted to verify that mine is doing this.

According to the two below screenshots from the manual it appears this is the normal way to wire the board. My question is how to verify the 47K resistor I circled is the one that is supposed to go to the 8 ohm tap and if in fact it is wired that way. Since according to the schematic I do have the correct 47K resistor circled and it is going to the correct tap.

I also have to go back and double and triple check to see if I did wire the inputs wrong as they attach to the board.


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## Guitar-Rocker

The 47K resistor, shown as orange, in the photo is the NFB resistor.


If you happened to omit the green wire (that is non-highlighted between the input jacks), then go back and add that in. And confirm your ground wire on the jacks is as shown, and is tied to ground.


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## Exojam

Both the input jacks are not connected as per the manual but both are tied to ground which I have verified.

And I do agree with your comment on the 47K resistor, I just want to verify it is tied to the 8 ohm tap as the schematic shows and I was if informed by Neikeel that is the way he really likes it and since he knows wayyyyy more than me I am going for the way he would do it.


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## neikeel

First need to sort the input wiring. On your painting you show the wires in black going from bottom of the high impedance socket (hi input straight to the 68ks. That is not totally correct. There are 2 pairs to the 68ks and these are linked to ensure switched grounding.
This is a nice clear image.





The ground wire is taken from the 1M resistor lug nearest the chassis front.


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## Exojam

I changed the input wiring to how it shows in the manual yesterday.

Going to fix the wiring to the preamp sockets and swap out the 47K bias resistor also.


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## Exojam

Well still a no go. I fixed all of the wiring issues I had found and also replaced the 47K bias resistor to a 33K which did allow for more adjustment. Reflowed all Top turrets. Put in new power tubes and also put new (NOS) tubes in V1 and V3.

Right now all four inputs work, I am hooked to a 8 ohm cabinet and do get volume from all 4 but it is still not cranking as I know it should.

I ran through all of the basic reading per the manual again (did not write them down this time) and they were close to last run around.

Hopefully in the next few days I can troubleshoot some more and also check out the Metro forum to see if anyone has ran into this before. Little bummed but it will be fixed and rock my house!


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## neikeel

Take a look at V1 pin7.
It is missing this is the grid wire from the junction of two of the 68k resistors on the channel 1. 
I’ll post this and keep scanning the rest of the pics.


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## Exojam

Thank you.


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## FourT6and2

Looks like you have your B+ rail wired wrong. PI node goes to 10K dropper then to one leg of the preamp filter cap. That junction goes to the CF on V2. The other half of the cap (after another 10K dropper) goes to V1 plate. But you have your halves connected wrong. That might be part of it.

EDIT:
Maybe you have this right actually. Just looks like you've flipped the two sides around, but still connected ok. But double check.


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## Exojam

Thank you for your response. I am not sure if you saw the link a few post up that has quite a few I believe good close-up shots of the guts of the amp.

Also I followed the steps pretty good I believe from the instructions so hopefully I did not wire to many things wrong

And on a side note, now I half to look most of the things you were talkings about since I am new to this.


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## Exojam

Neikeel,

What I found was:

I have continuity from V1 pin 7 to turret (measured off of resistor legs going into the that turret.

Anytime I have an input cable plugged into either bottom input on Vol1 or Vol2 I get around 68K going back to pins 2 or 7.

The top inputs never change from having around 34K on them no matter where an input cable is plugged in or no input cable being used at all.

https://www.dropbox.com/sh/ix5tkkoveim7quf/AACRGeAGPAmAV_w6OWnXrW5ma?dl=0


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## Exojam

NICE, half way there. I was doing voltage checks with a schematic from a 2204 master model that was very similar to my layout except for a few things. As I was doing this I found pins 2 and 3 on V2 were incorrect and needed to be swapped.

I did this and on input one it is rocking hard.

Not so much luck on input 2. Had some humming so I swapped all the preamp tubes and nothing. Pulled V1 and still had it. As it sits no hiss or hum from either of input 2 connections.

I know I have to go under the damn board again for the V2 pin 2 wire as I can move it and get fluctuations in noise.

I will keep plugging away as input one sounded mighty nice.


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## neikeel

Exojam said:


> NICE, half way there. I was doing voltage checks with a schematic from a 2204 master model that was very similar to my layout except for a few things. As I was doing this I found pins 2 and 3 on V2 were incorrect and needed to be swapped.
> 
> I did this and on input one it is rocking hard.
> 
> Not so much luck on input 2. Had some humming so I swapped all the preamp tubes and nothing. Pulled V1 and still had it. As it sits no hiss or hum from either of input 2 connections.
> 
> I know I have to go under the damn board again for the V2 pin 2 wire as I can move it and get fluctuations in noise.
> 
> I will keep plugging away as input one sounded mighty nice.



Nearly there!


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## Exojam

Just to make sure I am reading the schematic correctly. In the screenshot below I would like to verify:
Master volume 1 is circled in blue
Master volume 2 is circled in red


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## Exojam

Can someone please verify I have the pinout correct on this ECC83? Thanks.


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## Chris-in-LA

Exojam said:


> Can someone please verify I have the pinout correct on this ECC83? Thanks.
> View attachment 54371


Looks about right.


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## Exojam

Thank you.


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## Exojam

E

Since I had to go under the board to fix one of my wir s I replaced a few I did not like and finished up under there.

As I was cleaning up I dropped one of my matching NOS Mullard matching EL34’s and in slow motion I just watched it schatter everywhere. I was soooooo pissed at myself since I purchased those tubes specifically for this head.

I may try some Siemens NOS EL34’s for it now but have to do some looking around.

Neikeel, if this was your amp what power tubes would you be looking for?


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## neikeel

Your first choice usually. I have one quad left for my Ormat, then I am out
I quite like the RFTs/Siemens as these are probably best value NOS tubes out there now. 
Military Teslas are good (37 code) too but getting harder to find at decent prices. 
I use basic JJs on repairs for people and in fact have JJ KT77s in my ORST build and they sound pretty decent. 
You can send your tube to a big. Name supplier to match for you. Which is not cheap but better than a new pair. I had a nos GEC KT66 heater die on me but managed to buy a couple and get a good match. Sold the one that did not match.


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## Exojam

Thank you very much.

On a side note I am just stumped with channel 2. First time I could test it after going under the board.

Lower volume hiss than compared to channel one by a long shot. It will get pretty damn high if I turn up the presence control. 

Voltages appear to be around the board when I compare it to the 2204 master schematic but.......

I will keep trying, but now it is starting to bother me as I believe it will be something somewhat easy.


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## Chris-in-LA

Exojam said:


> Thank you very much.
> 
> On a side note I am just stumped with channel 2. First time I could test it after going under the board.
> 
> Lower volume hiss than compared to channel one by a long shot. It will get pretty damn high if I turn up the presence control.
> 
> Voltages appear to be around the board when I compare it to the 2204 master schematic but.......
> 
> I will keep trying, but now it is starting to bother me as I believe it will be something somewhat easy.


Just had a similar problem with my build, rolling tubes fixed it. See if that helps.


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## Exojam

Chris-in-LA said:


> Just had a similar problem with my build, rolling tubes fixed it. See if that helps.



All ready rolled them and no change. Pulled V1 as described in the manual and nothing.

Just measured all resistors and they are all of the correct values. I did not need to pull any of their legs except the 47K that sits next to the 10K and 8.2K ones. With both legs in, it was around 4K but when I pulled one leg it was the correct 47K value.


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## Chris-in-LA

I assumed that you might have done that. I’d probably go through everything with a chopstick at this point. Poke everything, tap on stuff, move wires, etc. See if that reveals any problems or odd noises. Mine’s pretty quiet but it hisses pretty good with everything on 10. Are you sure that the hiss is not normal?


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## Exojam

It just cannot be in my opinion.


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## Chris-in-LA

Exojam said:


> It just cannot be in my opinion.


So it’s louder than all your other amps?


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## neikeel

Things that cause hiss:
High gain (component values or settings). 
Component type (carbon comp resistors early in signal path some ceramic caps). 
First thing is to get channel 2 working then I suggest swapping out the carbon comps at least on your v1 grids


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## Exojam

Well I was in communication with valvestrom and he thought the wiring of the input may be wrong.

I redid the wiring and the inputs read correctly and switch to ground correctly.

In a few minutes I am going to do the pencil check and see what happens.

Neikeel, the resistors tied into V1’s grid are Allen Bradley ones, are those carbon comps?

Thanks to both you and LA.


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## neikeel

Yes, the Allen Bradleys are carbon comps. They can add what some people call a nice vintage vibe, what others might call hiss and noise. If you find the hiss unpleasant then it may well be worth replacing them, in particular the 68k grids, the 470k grids, the 1M input jack resistors, ie all those very early in the chain. The other thing that often causes hiss is when people use big bypass caps on the volume 1 pot (aka bright cap) as it selects out the high frequencies and amplifies them above all other frequencies.
Silly things to check will be that you have not swapped the two brown wires to vol pot on channel 2.
Your pics, whilst nice and clear, do not give an over view of the whole board and the front and back of the chassis so you have to jump back and forth trying to trace things out, looking for the likely simple wiring error or dry joint.

For MF resistors I have used these:





https://www.ebay.co.uk/itm/5-X-1M-o...he rest of the amp, they sell them in 68k, 1M,


----------



## Exojam

Thank you Neikeel.

Right now I am at a standstill until I can get out into my shed as I blew a few earlier. 

I also want this back out in the shed since over my workbench I have a very good 2*4 led panel which gives great light and I can roll my wheelchair under the bench so I can reach everything better.

I have not lost faith on this yet. I am just disappointed in myself since I try to take my time and do everything nice and clean and expect the project I am working on to work when fired up.


----------



## Exojam

Neikeel,

That link in your post is not working.


----------



## neikeel

Try now.
I tend to use Pihers in my builds but got these recently to do a turret board build of a 1987 reissue.

Oh and don't give up. I had a ground loop hum on my Matamp build that nearly drove me mad (it uses wire shields everywhere for grounding), but I found the culprit and it is quiet as a mouse now!

So message is keep going!


----------



## Exojam

Neikeel,

Thanks for working on the link.

Can you verify the the one pins and components that should have any effect on Volume 2 are highlighted in the below screenshot. Could you also verify my post 85 questions.

And one last one for now. Since there is a .68uf caps coming into play with vol 2 and I do not have anymore Zoso's, would you stick with them or maybe change to the type we went with earlier where we changed the original value one of 220uf to a different value? 

Thanks again, James


----------



## neikeel

The first 0.68 is channel 1 cathode cap and is just channel 1. The corresponding channel 2 is the 250uF/820R in end of board. 
The second 0.68 is on V2a cathode (with the 820R) and is common to both inputs. 
Start with channel 2 jack’s going to the 68ks and via the green wire to v1a socket. Signal comes via the blue wire on v1a through the v1a 0.022uF cap to the first lug on vol2 pot. Then the wiper goes to the first 470k resistor. After that everything is common to both channels. Do you need to check the cathode RK connections, the grid and plate wire connections and the correct coupling cap and wires to the pot (check pot value and it’s ground connection) and the connections to the non-bypassed 470k resistor.


----------



## Exojam

I added 4 more pictures that I think you wanted. They are just named 1,2,3 and 4.

I will do the resistance check on the areas you described above.

https://www.dropbox.com/sh/axn4iuo7ab5td07/AAATw8j5EAHUQ18GhJr2it2ea?dl=0


----------



## neikeel

That type of pic is very useful as they are clear, you can zoom in and move the cursor to trace the wires.
From the picture I am still not convinced your input jacks are wired correctly (afraid can't tell from your pics)
This pic is ok but it is confusing as the two green wires from the switching jack lugs are shown coming together.




The top lug on the top jack goes to one 68k and the bottom lug on the top jack goes to the other 68k. 
The black earth wire goes from the lug on the bottom jack lug closest to the chassis wall (where the 1M resistor and the link wire join).


----------



## Exojam

I will unscrew them from the chassis and get side shots of them.


----------



## Exojam

I have placed some close up shots of the iput jacks. They are V1, V1A, V2, V2A and V2B.

Let me know what you think. Thanks.


----------



## neikeel

The jacks look to be wired correctly and the hook ups look correct too.

If you are sure that there are no dry joints on those grid wires (before and after the 68ks and yoy have tried different ECC83s in V1 then you need to double check the components (Channel 2 pot values, the bypass cap, a 220uF you said? and the AB 820R cathode resistor are all in spec.)
If all of those things (and the jack grounding is correct there is nothing else, particularly if channel 1 is working normally.


----------



## Exojam

I can measure them out and swap them if I see something but I do not have any fuses for it right now. I thought I had them in my shed but they are the other fuses the amp needs so I am about to order some.


----------



## Exojam

While I am waiting for my fuses, I am reading how tube amps work from the below page.

Very interesting as I had no idea how the signal flowed and how the first tube (and others) were split into V1A-V1B etc. And with the questions Neikeel is asking me I figured I better understand this stuff a little better.

https://robrobinette.com/How_Amps_Work.htm


----------



## Exojam

Neikeel,

I did the testing as you had suggested and everything comes out fine. I downloaded some more pics to the link below.

i guess at this time it is either a bad component or a bad solder joint. My plan is to pull all of the components we discussed and resolder them back in. I am also going to take off the 820R and put some jumpers on the the cap so I can test another 820. If all that fails than I will replace one component at a t time to try and get it working.

https://www.dropbox.com/sh/jv2qz4vsweuy5up/AADNAKMB_ywy64GakNpz8GXwa?dl=0


----------



## Exojam

Components taken out for testing.

View media item 10512


----------



## Exojam

Well still a blanking no go.

I replaced the 50uf cap that has the 820 ohm resistor one it, the 50 went in place of the schematics .68 cap.

Also replaced the the zoso .68 just for fitting purposes, this is the one closet to the end of the board.

Losing hope of this build as of now. Just pretty fucking disappointed!


----------



## neikeel

So channel 1 is still working?
Are you still getting heater voltage on both halves of V1?


----------



## Adieu

neikeel said:


> The first 0.68 is channel 1 cathode cap and is just channel 1. The corresponding channel 2 is the 250uF/820R in end of board.
> The second 0.68 is on V2a cathode (with the 820R) and is common to both inputs.
> Start with channel 2 jack’s going to the 68ks and via the green wire to v1a socket. Signal comes via the blue wire on v1a through the v1a 0.022uF cap to the first lug on vol2 pot. Then the wiper goes to the first 470k resistor. After that everything is common to both channels. Do you need to check the cathode RK connections, the grid and plate wire connections and the correct coupling cap and wires to the pot (check pot value and it’s ground connection) and the connections to the non-bypassed 470k resistor.



Wow it's THAT simple a curcuit?


----------



## Exojam

Neikeel,

I did not check heaters earlier.

It seems like since I was switching tubes I am getting lower measurements.

Tomorrow I will try and remember what tubes were wheat and document them and post them.


----------



## Exojam

Neikeel,

I apologize but I could not get heater readings as one of the wires going to input 1 broke from under the board so I did not want to power it up.

I just really think the issue is with the input jacks wiring based of what Robert from valvestrom sent me (see below).

“Guessing that you have the jacks wired wrong. When in the top input, the 68ks are wired in parallel; when in the bottom input, one 68k is switched to ground and the input signal goes to the other one. I suspect somehow you are switching the input signal to ground.”

Input 2 never seems to switch to ground when I am plugged into Input 1’s bottom which I believe should be happening the way I read his message.

It just makes no sense since I have these wired as the manual states they should be. I have reached out to him for a bit more detailed information.


----------



## Chris-in-LA

This is the way that Mojotone wires the inputs on their JTM45. What about using this type of arrangement?



@Exojam


----------



## RickyLee

Exojam said:


> Built a little stand so I can my measurements with.
> 
> View media item 10428



First off I just want to say that your build looks great on your craftsmanship. I always admire people with much more patience than myself on this stuff.

And I hope your health gets better as well. And take care of your ears as well when it comes time to crank that bad boy up when you get it sorted. I have been going through a 3 week scare with my hearing, constant bad ringing, and started on antibiotics after I finally went to the hospital Wednesday night. Hoping it is a simple infection and this crap clears up. Anyone reading this, please take caution with your hearing!

Regarding the issue you are having on input 2, I wanted to ask if this is a 2203 or 2204 type build? On your input 2 jack problem, I got confused as I thought I read some info on a Plexi/four holer type values/branches in some past posts. Just saying in case there is a simple mix up or overlook there between others helping.



neikeel said:


> You can do both but I would go for the red line, that keeps all AC well away from any signal wires.



I have some questions for your expertise and experience. On my 2555 Jubilee Clone build, I used Classic Tone iron. At the time I installed the transformers back in 2011, I never trimmed down any of the working leads as well as all the extra aux wires my power transformer has (40-18069). I basically sealed, twisted, tucked them all together into the corner of the chassis away from everything best I could all those years ago. This was due to possibly wanting to swap all the iron out later to period correct 100W Dagnalls I have. I am not having any noise issues that I can tell. Just curious as we are all looking for every edge we can get on the noise issues.

So basically I am wondering if this is an issue with hum or noise in an amp having all that excess transformer wiring inside?

Also, regarding the heater filament wiring runs and twist, is there a preferred twist direction starting at the power transformer going down the line that should be implemented? lol Obviously this is AC, but then it seems like I have noticed many many pics of builds using the counter-clockwise twist going out from the power xfmr.


----------



## Chris-in-LA

RickyLee said:


> First off I just want to say that your build looks great on your craftsmanship. I always admire people with much more patience than myself on this stuff.
> 
> And I hope your health gets better as well. And take care of your ears as well when it comes time to crank that bad boy up when you get it sorted. I have been going through a 3 week scare with my hearing, constant bad ringing, and started on antibiotics after I finally went to the hospital Wednesday night. Hoping it is a simple infection and this crap clears up. Anyone reading this, please take caution with your hearing!
> 
> Regarding the issue you are having on input 2, I wanted to ask if this is a 2203 or 2204 type build? On your input 2 jack problem, I got confused as I thought I read some info on a Plexi/four holer type values/branches in some past posts. Just saying in case there is a simple mix up or overlook there between others helping.
> 
> 
> 
> I have some questions for your expertise and experience. On my 2555 Jubilee Clone build, I used Classic Tone iron. At the time I installed the transformers, I never trimmed down any of the working leads as well as all the extra aux wires my power transformer has (40-18069). I basically sealed. twisted, tucked them all together into the corner of the chassis away from everything best I could all those years ago. This was due to possibly wanting to swap all the iron out later to period correct 100W Dagnalls I have.
> 
> So basically I am wondering if this is an issue with hum or noise in an amp having all that excess transformer wiring inside?
> 
> Also, regarding the heater filament wiring runs and twist, is there a preferred twist direction starting at the power transformer going down the line that should be implemented? lol Obviously this is AC, but then it seems like I have noticed many many pics of builds using the counter-clockwise twist going out from the power xfmr.


You will get a lot of opinions about twisted heater wiring. I don’t believe that there is a wrong direction. Many will tell you it has to be tight but here’s a pic of my stock 2204, not especially tight and it works fine. You can duplicate the direction of the twist and you can make it tighter if you want.


----------



## Exojam

LA,

I am going to see if Robert from valvestrom replies back to me since it makes absolutely no sense that this is taken place. 

I went back through old photos and verified again, that I wired the board correctly and also the inputs. I ran out of green wire so I ordered some more and both inputs are coming out and being rewired. Add in the fact I double and triple checked the wiring with continuity checks and all is correct. Just some in two damn inputs that are kicking my but, how sad.


----------



## Chris-in-LA

Exojam said:


> LA,
> 
> I am going to see if Robert from valvestrom replies back to me since it makes absolutely no sense that this is taken place.
> 
> I went back through old photos and verified again, that I wired the board correctly and also the inputs. I ran out of green wire so I ordered some more and both inputs are coming out and being rewired. Add in the fact I double and triple checked the wiring with continuity checks and all is correct. Just some in two damn inputs that are kicking my but, how sad.


It’s too bad that this thing is causing you so much trouble. You’ll get to the bottom of this I’m sure. I spent some time going over your pics and posts but I can’t figure it out. The pics are no substitute for actually having physical access to that amp.


----------



## RickyLee

I was just curious to know the input scheme. Is it a 2204 type High/Low?

Reason was I thought I read some posts regarding a Plexi gain stage layout which translates to the four input design. Just checking. Title mentions "Plexi".


----------



## ampmadscientist

Exojam said:


> E
> 
> Since I had to go under the board to fix one of my wir s I replaced a few I did not like and finished up under there.
> 
> As I was cleaning up I dropped one of my matching NOS Mullard matching EL34’s and in slow motion I just watched it schatter everywhere. I was soooooo pissed at myself since I purchased those tubes specifically for this head.
> 
> I may try some Siemens NOS EL34’s for it now but have to do some looking around.
> 
> Neikeel, if this was your amp what power tubes would you be looking for?



NOS tubes can have all types of problems.
For one thing many of these tubes are not NOS. They are just old used tubes.
I consider these type tubes a huge waste of money, since they are usually unreliable.

I would definitely test an amp with new tubes.

There is no advantage to using old tubes....it will just cause a lot of headaches.


----------



## ampmadscientist

neikeel said:


> Things that cause hiss:
> High gain (component values or settings).
> Component type (carbon comp resistors early in signal path some ceramic caps).
> First thing is to get channel 2 working then I suggest swapping out the carbon comps at least on your v1 grids



The majority of hiss is only caused by one thing: the 68K input resistor.
This 68K contributes about 70% of the total hiss in a tube guitar amplifier.

(we have tested this extensively, with real test equipment)

The carbon resistor is the noisiest possible resistor.
Wire wound or bulk metal foil is 40 db quieter than a carbon resistor.

Your second choice is metal film resistors.


----------



## Exojam

RickyLee,

It is a JMP 50 or early 2204 as I have been told.

Thank you very much for your comments concerning my health. I will just leave it as it is still ongoing and since Dec 16, 2016 I have had to be admitted over 70 times. You just want it to be over so I can continue my little life.


----------



## Exojam

RickyLee said:


> I was just curious to know the input scheme. Is it a 2204 type High/Low?
> 
> Reason was I thought I read some posts regarding a Plexi gain stage layout which translates to the four input design. Just checking. Title mentions "Plexi".



That is correct, high low on both inputs. One on top of the other.


----------



## RickyLee

Exojam said:


> That is correct, high low on both inputs. One on top of the other.



Got it. So then your Low input or input 2 you are hving the issue with should be entering the circuit after the 1st gain stage and before gain pot and 2nd stage.

Your High input has to travel through Low input when contacts are closed.


----------



## neikeel

Chris-in-LA said:


> This is the way that Mojotone wires the inputs on their JTM45. What about using this type of arrangement?
> View attachment 54850
> 
> @Exojam



Trace the wires out and you will find it is the same


----------



## Exojam

Well at this I am not sure were to go. Did a lot of work on it yesterday and today and still no input two.

I completely replaced all the wiring on both inputs, in selected turrets that seem to keep breaking wires, I ran the wire up the back side of the turret and put a few wraps on the leg of the component that goes into that turret slot.

I have already replaced the 50uf cap that has the 820 ohm resistor one it, the 50 went in place of the schematics .68 cap. I could get to readings on 50uf cap and that is why it went.

Also replaced the the zoso .68 just for fitting purposes, this is the one closet to the end of the board.

All my pictures show I have this thing wired correctly. Just tested the .022uf cap that goes between the sets of 68k resistors and can watch it charge and discharge very fast.

I will link in all my readings and photos from today sometime tomorrow but again at this time something on the board is failing and it is not my dang wiring. 

Just do not have any idea where to go from here since I have checked this thing out a million ways to Sunday.


----------



## Exojam

https://www.dropbox.com/sh/m5d6gxs7e9bsrmu/AAD2h4_foJI1dOoIr7mZhVEja?dl=0


----------



## Exojam

Well it just goes to show, do not depend on the “hiss” from the speakers as described in the manual to validate your amp is working, plug a freaking guitar into all into inputs.

Than you will (hopefully) find out your amp IS WORKING!!!!!!!!!!

Damn, I thought I was never going to get this girl running, feels damn good.

Now I just have some cleanup work to do to fix some components that I do not like the look of, solder on the 820 and 2.7k ohm resistors I had clipped onto their respective caps.

Neikeel,

Based on our conversation where had stated the below:

“channge the 0.1uF PI output couplers to anything between 0.022uF to 0.047uF (0.022s are expensive but you can get 0.027uF 0.033uF or 0.039uF or 0.047uF much cheaper in 400v rating)”.

Should I go ahead and change out the .01uf caps while the amp is still open? I know I have one .022uf Zoso left but would need to search my parts to see if I have another cap in that value. If I only have the one I was thinking of putting it on the presence pot. Than get another cap for the .01uf cap coming off of V3 pin 7 (I believe that it were it goes).

I cannot thank you enough for all of your help you provided me in getting this amp together, but again THANK YOU!


----------



## neikeel

Thank goodness
I would change no components, if the last pics are correct you already have 0.022uF in the PI output slots which will be fine
Just play it and bed it in.
Tweak the bias to the sweet spot and get some hours onto it, it will get sweeter and nicer to play.
Mod it later.


----------



## Exojam

Sounds good.

Thanks, James


----------



## Exojam

Well I tried the below combination of tubes and am not impressed. The tubes in V4-5 had to go as they were blowing the 3 amp fuse so I just dropped some JJ’s in there.

V1 - I63 Ice (Mullard)
V2 - 12AX7 Raytheon JAN
V3 - GE 5751
V4/V5 - Amperex XF2 6CA7

On either input on Input 1, the low E,A and D sounded like they had no definition at all. They were just sounded like the volume was way passed it limits and made everything rattle. Not like it was a clipping sound.

On the G, B and high E it just sounded like an ice pick.

On Input 2 either top or bottom, it made it sound like the amp was covered in a blanket and no string had any definition. I am not sure if the Input 2 selection is supposed to a few dB lower than Input 1 or not.

Not even sure if I want to keep testing with those tubes with the sound I am getting or change them up.

May need to change that cap on volume 1 channel pretty quick.

Also, not very impressed with the overall volume levels on the amp as I feel my modded DSL40C is much louder.

I will keep on trying.


----------



## Chris-in-LA

Your description of channel 2 sounds about right, that’s why i rarely use that channel.


----------



## neikeel

either a 5000pf cap on vol 1 or 100pf.

- nothing in between!

Are those JJs old an are they biased correctl?


----------



## Exojam

Yes the JJ’s were biased correctly. I am taking the plate voltage and putting it into a bias calculator to get my target bias value.

I decided to put two non matching EL34’s in there since I cannot find any technical documentation that states this cannot be done. I was actually looking for multiple tech docs on non matching power tubes and could not find any. Right now they are biasing just a few millamps apart high I see even with matching tubes in this amp.

I will see if I have either one of those caps.

I also may have been to quick on the evaluation of the amp last night. After my first session with it, I just left it on for a few hours so everything could start to break in - settle in and things sound more satisfying.


----------



## Exojam

Damn and the only one I have is in between (capacitor) for volume 1.


----------



## Exojam

neikeel said:


> either a 5000pf cap on vol 1 or 100pf.
> 
> - nothing in between!
> 
> Are those JJs old an are they biased correctl?


Any specific type/manufacturer for that cap? Thanks.


----------



## neikeel

Nothing specific, minimal voltage there, original were 5000pF (5nF) LEMCO ceramic discs and the 100pF ones either RS red tubular ceramic or later Murata ceramic discs.


----------



## Exojam

Well back to work on the amp. There is something wrong with the biasing. I believe it is V5 that only bias’ at half the current as V4.

At first I thought is was something that went wrong with the other tubes I had in there so I pulled them nd other things to do so I had forgot about it.

I just put in the matching Millard’s and it showed up again.

More bench time and no playing time on it, fun, fun.


----------



## ampmadscientist

Exojam said:


> Well back to work on the amp. There is something wrong with the biasing. I believe it is V5 that only bias’ at half the current as V4.
> 
> At first I thought is was something that went wrong with the other tubes I had in there so I pulled them nd other things to do so I had forgot about it.
> 
> I just put in the matching Millard’s and it showed up again.
> 
> More bench time and no playing time on it, fun, fun.



Test the screen grid resistors.


----------



## Exojam

Thank you.


----------



## ampmadscientist

Exojam said:


> Thank you.



Do you know which ones those are?


----------



## Exojam

If I researched it correctly they are the Xicon 1K 5 watt resistors that go between pins 4 and 6 on V4/5.


----------



## neikeel

Check the solder connections on the tubes and where the green and orange wires come off the board. 
Also check the quality of the grounds on both octal tubes ( ideally a dedicated ground to the bias caps. 
If you have 1 ohm resistors and they are small they can act as fuses if you have a short in a tube so check both are intact.


----------



## Exojam

Interesting about the 1 ohm resistors.

I just measured the 1K resistors and they were fine BUT they were completely in the system so I will get my soldering station and left a leg on the just to make sure I get a proper reading.


----------



## Exojam

Well I think you hit it Neikeel.

V4's resistor is reading 1.2 ohms
V5's resistor is reading .6 ohms

Also, if you look at the pictures in the link below, it appears that V5's resistor has been just a tad overheated. I will see if I have any of these 1 ohm 1 watt guys floating around around.

Thanks again to you and Amp.

https://www.dropbox.com/sh/dpkterawmkp0q7i/AAAhINuVh1MsxeC5Eq21yI0Va?dl=0


----------



## neikeel

These should be 1ohm 1 watt and 1%. 
Personally I no longer use them and use the primary resistance/voltage method


----------



## Exojam

I had about 6 of them in my stash (same resistors that were in the system).

I replaced V5’s but am still seeing about a 4ma difference between the two valves. I will probably replace the V4 resistor tomorrow just to have 2 new ones in there.

I have not heard of the method you use so I would have to research to know what I would be doing.


----------



## neikeel

http://www.marstran.com/50W Bias.htm

Just use insulated leads, a good meter and be careful.


----------



## Exojam

Thank you.

I use a Fluke 115, not the best but it is nice enough.


----------



## Exojam

neikeel said:


> http://www.marstran.com/50W Bias.htm
> 
> Just use insulated leads, a good meter and be careful.



So I just read through that a few times and it never mentions any resistor, so do you need to remove the 1 ohm, 1 watt, 1 percent resistor from the system?


----------



## neikeel

That is why I mentioned it as I don’t use the resistors myself. I like the solid ground connection direct to the bias cap ground.


----------



## Exojam

Gotcha, thanks.


----------



## ampmadscientist

Exojam said:


> Gotcha, thanks.



If you are replacing 1 ohm cathode resistors, it's better to use 1% resistors.
Most resistors are going to be + / - 20% which is a pretty big difference when you are measuring.


----------



## neikeel

neikeel said:


> These should be 1ohm 1 watt and 1%.



Sometimes that AMS guy is just on broadcast and not receive!


----------



## Exojam

OK, I get every reading till I am actually trying to set the bias. Below are my reading and when I need to use the CT I am using the turret that has both the brown primary OT and on leg of the choke. This turret sits above the power tubes but almost right in the middle.

V4 = 37.3 ohms - 449VDC - 38.9ma - 1.45VDC
V5 = 38.8 ohms - 448.2VDC - 39.0ma - 1.51VDC

Not sure why everything gave me a reading but where I am trying to get the last values (hum hum hum).

https://www.dropbox.com/sh/hlnvl6382l65b4g/AAA-xjKDnxQIH3i0fKRdYJn1a?dl=0


----------



## neikeel

That should be correct.
if plate voltage (pin3 to ground) is 449vdc and your resistance is 37.3ohms then if you measure the plate voltage drop between the OT centre tap (brown wire) and pin 3 of V4 you should be shooting for 1.45vdc

using your other numbers for pin 3 of V5 shooting for 1.51 should get you to a similar figure. Sometimes swapping valves over gets you closer.

Are you getting a hum or redplating?

If so just start at the max you have there and gently, slowly decrease the bias until it sounds good (have the guitar there, plugged in and try it). Only turne the signal off when measuring.


----------



## Exojam

Neil,

That is my problem, when I am at the last step, connected to either pin 3 and the center tab, I get no voltage readings at all, even after adjusting the bias pot. Both meters just read zero volts.

No humming or red plating.

Also, just to be clear I did remove the one ohm resistors.


----------



## Exojam

I am just wondering if I should be using the OT CT wire that is attached to the choke wire or the CT wire that is going to the standby switch.

***correction***
Should I be using the OT CT wire that is tied between the lamp and the mains on/off?

And that document, at least to me makes me feel I should actually be reading such a low voltage, around the 1.5 area.


----------



## Exojam

Also, on this statement:
“if plate voltage (pin3 to ground) is 449vdc and your resistance is 37.3ohms then if you measure the plate voltage drop between the OT centre tap (brown wire) and pin 3 of V4 you should be shooting for 1.45vdc”

It sounds like when I measure between the OT CT (brown wire) and pin 3 I should be reading right around 450.45 VDC since that is a 1.45VDC difference between the two measurements (a 1.45 VDC voltage drop).


----------



## neikeel

No
First measure plate voltage pin 3 to ground write it down (450v)
Next measure pin 3 to centre tap = voltage drop (you are not measuring a difference - just the number when probes between the CT and pin 3) which should ideally be 1.45vdc.
V=IR 
V= bias current x primary resistance
Desired voltage across primary (Vp) = 17.5/450 x 37.3
Vp = 38 x 37.3
= 1.45v


----------



## Exojam

Neikeel,

The only place I can measure the OT center tab is circled on the screenshot and no matter what it will not give me a reading when going from it to pin 3 on either power tube.


----------



## neikeel

That is not possible (original 50w use the HT fuse holder as that tie point but we should not worry about that - just reference!).
The turret is the OT centre tap with B+.
You have successfully measured the resistance.
There will be volts across the primaries of your plates if the amp is making sound you are just not measuring it!
Are you using the correct range on your Fluke? Some DVMs have buffers that prevent accurate readings here but your fluke should be fine.
There will be volts - you just need to measure them


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## Exojam

Neikeel,

A few questions.
1) are you saying there should be other places to measure the OT center tab
2) when you say “there will be voltage across the primary’s”, this is of coarse if I have one?

I made a videthat was only about 4-5 minutes for you but it is taking over a day to try and get it to Dropbox.

I will take some more pictures but if you look at page 18 of the manual, you will see how the only place the brown wire from the OT goes to the choke.


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## neikeel

Your amp CT is fine there
If you have sound you have voltage


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## RickyLee

To verify you have the CT, measure power tube sockets resistance from pin 3 to pin 3. Should be exactly double what your CT to each pin 3 is. This is with amp OFF.

CT should be on the upstream side of the choke. Might be able to attach on the pos filter cap as well. Be careful.


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## Exojam

Yes, the Pin 3 to Pin 3 added together does come out to them being measured individuals.

I am sorry, guys I am not trying to make this hard or be a pain in the ass, it is just one of things that is not clicking for me.

I went over the schematic a million times and looked at what is in front of me and just cannot put 2 and 2 together as to where I can put one probe one pin 3 and figure out where the other probe is to go to get me the 1.5vdc.

I am also scouring the internet looking for the answer.


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## Exojam

Here is a link to the video I was talking about, i hope it helps shows you what I was talking about.

https://www.dropbox.com/sh/hlnvl6382l65b4g/AAA-xjKDnxQIH3i0fKRdYJn1a?dl=0


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## Exojam

Think I have it.

Some guys pointed out that if the one ohm resistor get pulled, a wire needs to go in it’s place to provide grounding.

I just thought the one ohm resistor was in there for biasing purposes. 

I will test it out tomorrow.


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## Exojam

I know it is not the best picture but does it look like red platting?


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## Chris-in-LA

Doesn’t look like red plating to me. I can’t see any red on the plates in that pic.


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## Exojam

Thank you.


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## Exojam

Well I was just testing the amp after I made something for it to sit on till I make the head case and moved it into the guitar room.

On inputs 1, I was at about 6 on Input 1 volume with my guitar volumes around 7 till it really started to kick in. I was just playing like an open E, open A and G5.

Strange thing though, I could have sworn that when I moved the volume 1 knob to around 8 or a little more now with my guitar volume also around 8, it sounded like there was a drop in volume. I will have to check the packaging again to see what bright cap I put in there.

On inputs two I had to move the presenceand treble to around 5 and than I started to like the sound.

Bass and mids were also around 6.

Oh and it does sound mean as hell, like someone really pissed it off.


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## Exojam

Is it normal for this model to need to be up around on the volume before it really starts screaming?

I can have it at around 6 and use my guitar volume controls but do not get the same sound from it as I do when the volume is at around 8.

Still rolling tubes to see what sounds good to me.


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## neikeel

Put a 5000pF bright cap on it


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## Exojam

I think I am going to try out this Sylvannia/Baldwin 12AX7 single halo I just received in V1.


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## coolidge56

Exojam said:


> Is it normal for this model to need to be up around on the volume before it really starts screaming?
> 
> I can have it at around 6 and use my guitar volume controls but do not get the same sound from it as I do when the volume is at around 8.
> 
> Still rolling tubes to see what sounds good to me.



8 is the sweet spot, 9-10 the quality of the tone begins to fall off imo.


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## Exojam

So yesterday I decided to make some measurements of the the system I was using looking at harmonics and a waterfall to see how bad my "guitar" room is.

So the equipment being used is as follows:
SG Gothic with David Allen Powerage pickups.
The amp I just built in this thread with matching Mullard XF2 Single Halos for power tubes,
V1 - Baldwin/Sylvania 12AX7
V2 - GE JAN 12AX7A
V3 - Raytheon JAN 12AX7
Mesa Recto Rectifier 2x12 Cab Cabinet Celestion V30s England
Setting of the amp are in a screenshot and guitar volume and tone were around 6

Show with the screenshots, I split them up in a few ways. One has the fundamental and all harmonics, one has the fundamental and even harms, one has the fundamental and odd harms and maybe one more, there is a screenshots of the amp settings and one waterfall.

wondering what some of you guys think of the harms, as for the waterfall (which I knew before even taking this one) is that the room I play in ABSOLUTELY SUCKS for acoustics.

All harms in %



even harms



fund and all harms



fundamental



odd harms



waterfall


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## Exojam

I added another one real quick that changes the scale to db relative and i hovered over the fundamental so it is in yellow and easy to pick up which may make it easier to compare the harms to it.


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## ampmadscientist

Exojam said:


> I added another one real quick that changes the scale to db relative and i hovered over the fundamental so it is in yellow and easy to pick up which may make it easier to compare the harms to it.
> 
> View attachment 56280



"...the room I play in ABSOLUTELY SUCKS for acoustics."

Install some bass traps in the corners of the room, and it can be a whole new amazing world.


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## Exojam

Amp,

That is the plan. I have corner traps and other panels in my family and man do they make a world of difference.

I still (I believe) a whole box of 2”*2’*4’, 12 sheets of 203 in the basement I can use. I just need to pick out some fabric and build some frames.

Not sure why more home players like myself do not do this in the guitar world. When I was big into speakers and subs it seemed more people would do this.


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