Valvestate 8100 & 8080 PCB improvement

bobylapointe69300

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Hi,

This thread just to get a few advices from Marshall 8080/8100 users/modders/tweakers.

I have 2 amps, 1 x 8100 head, and 1 x 8080 combo version (12" speaker). I am attached to these amps as I have had them for a long time now, starting learning guitar with and like their overall sound.

But they are not perfect as you know, and weakest link is probably their PCB quality. I started facing difficulties to unsolder/solder components, getting fried soldering pads, also suspecting a conductive board in some areas making troubleshooting difficult... This JMP59/PC0689 PCB board, common to both amps, is corresponding to 90's standards when it comes to PCB production...

Not many options for me here as main fixes you use to repair trace is quite temporary, and a standalone PCB is not available unfortunately, so I had to go the difficult way and replicate this PCB on my own. Hopefully I owe decent equipment to unsolder components, and a lot of free time.

In the process, I torn down all components, removed the steel potentiometers bracket, heatsink, reverb connectors,... so that I could scan the board with high resolution and work on this in sprint layout software. This was tight as software is limited to 500mm in board length, so I managed to reduce current board length.

Here is the list of improvements I did on initial design:
1) use of a double sided PCB to integrate all links as part of top face with via holes (removes risk of bad links and reduces soldering time)
2) add a ground plan to each side as they were missing on initial design
3) add wire onboard connectors for reverb essentially (for maintenance and removal of board)
4) modification of TR8 and TR10 package to accept new generation transistors TIP 141 142 147... that have a different package (BDV64 and BDV65 are obsolete, but easily replaceable by TIPXXX)
5) indicate components values directly on the board (silk mask) for easy replacement
6) integrate a simple diode protection circuit for IC1 (very sensitive to static electricity and not that well protected on current design) on pin 5

My question is : would you see any mandatory improvements I should make before moving forward ?

Thanks for the hints.

Here are lowres top and bottom view of the board :
TopC1-S1-lowres.JPG
BottomC2-S2-lowres.JPG
 
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Saunatonttu

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Wow! Having just purchased an 8080 I haven´t run into these troubles you mentioned, though the amp itself may have. Work has been done on it. Very cool to see someone doing this. Sadly I´m no electrician so didn´t understand half of what you wrote and therefore cannot contribute.
What could this protection for IC1 be like? Could it be made without a new board by simply soldering parts together?
 

bobylapointe69300

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Hi, Thx for your message. IC1 protection is something that was missing on valvestate very first series. MARSHALL implemented it when they did the new generation, and for example this is what is present on a MG10CD:
Untitled.png
So you can probably wire this way for 8080/8100 series :
8080-8100-IC1-protection.png
You can find +15V/-15V in various locations on the board, I used R64 and R65.
 

bobylapointe69300

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Just a tip, if you are not confident with soldering and so on, let a friend do it for you ;). Also pay attention to polarity of diodes and insulation of wires if you solder it on the back of the PCB.
 
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Saunatonttu

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Soldering will not be a problem, though circuit boards are not that familiar to me. Thanks for the tip, my initial instinct was indeed to do it in the back with shrink tubage to prevent shorts. Besides, diy and learning is a big part of this excercise.
 

Saunatonttu

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Yes, well now it works. Did the diod thing to protect IC 1, replaced the R 12 with original value and installed a speaker jack in the very same hole the cable went through before. No drilling required!

_DSC9759 IC suojausdiodit.jpg
Thanks again for tips. Soldering on the board was quite difficult so perhaps it´s best to have a board that has this designed in.
 

wakjob

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I have an 8100 and the 8080...I know these issues well.
But I have nothing to add, other than I'd be interested in one of your new boards if/when you get them.

I've reflowed every point on the 8080, and still get volume drop...
Whack the top of the amp, and it comes back.

It's that atx1 auto transformer...getting harder to find.
The second gen. designed a tap in the PT for the heaters...much better.
 

bobylapointe69300

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I have an 8100 and the 8080...I know these issues well.
But I have nothing to add, other than I'd be interested in one of your new boards if/when you get them.

I've reflowed every point on the 8080, and still get volume drop...
Whack the top of the amp, and it comes back.

It's that atx1 auto transformer...getting harder to find.
The second gen. designed a tap in the PT for the heaters...much better.

I'll let you know when I place the order. Autotransformer is known as T5899 or T589 or metxvshv, and you can find it here:
- https://www.algam-webstore.fr/marshall-transfo-t5899-de-8080-txau-00003-97110.html
- https://www.tubeampdoctor.com/en/marshall-transformer-for-ecc83-supply-in-valvestate-8080-etc
- https://www.retroamplis.com/epages/62070367.sf/en_GB/?ViewObjectPath=/Shops/62070367/Products/TRA-METXVSHV


As an extreme option, you could try to "rework" the winding, this used to be done in the past, but might not be worth here as a T5899 does not cost a lot. You need to be meticulous (counting the number of winding turn, how the wires are arranged, located...) and need to make yourself a fixture to ease the winding.
 
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wakjob

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I'll let you know when I place the order. Autotransformer is known as T5899 or T589 or metxvshv, and you can find it here:
- https://www.algam-webstore.fr/marshall-transfo-t5899-de-8080-txau-00003-97110.html
- https://www.tubeampdoctor.com/en/marshall-transformer-for-ecc83-supply-in-valvestate-8080-etc
- https://www.retroamplis.com/epages/62070367.sf/en_GB/?ViewObjectPath=/Shops/62070367/Products/TRA-METXVSHV


As an extreme option, you could try to "rework" the winding, this used to be done in the past, but might not be worth here as a T5899 does not cost a lot. You need to be meticulous (counting the number of winding turn, how the wires are arranged, located...) and need to make yourself a fixture to ease the winding.

Yep...ordered mine for the 8080 from TAD.
I think it was like $65-ish dollars to get it here to the states.
But, I needed it.
 

bobylapointe69300

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I have an 8100 and the 8080...I know these issues well.
But I have nothing to add, other than I'd be interested in one of your new boards if/when you get them.

I've reflowed every point on the 8080, and still get volume drop...
Whack the top of the amp, and it comes back.

It's that atx1 auto transformer...getting harder to find.
The second gen. designed a tap in the PT for the heaters...much better.

Final PCB design just below:
Export-Top-C1-S1.JPG
Export-Bottom-C2-S2.JPG
Last changes I made is replacing solder connection of wires with male terminals 6.35 mm (similar to newer amps):

HTB1O3atda1s3KVjSZFAq6x_ZXXaW.jpg

More convenient if having to work on the PCB.

Here's a picture of my beta board (ie not including all modifications):
DSC_0050.JPG DSC_0059.JPG
 

Guga Ramone

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Long time lurker, first time poster. Had to log in just to say what an amazing work you've done! Congratulations on your effort in keeping those little beasts of amps screaming.

I own an 8080 and also have worked on a few of them and know all those problems you listed. If there's still time to mods, I'd add the protection diodes also after the FX Return, on pin 3 of IC6. Also, using higher wattage resistors and zenner diodes on the power supply and on the tube supply helps to tame the temperature and future failures. Regarding the tube autotransformer, they are impossible to find here in Brazil and very expensive to import, so in a desperate attempt to keep the amp running, one may bypass the tube stage completely and add gain back in a further IC stage (IC5b).

Would you mind sharing the high resolution PCB?

Thanks and cheers from Brazil!
 

bobylapointe69300

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Hi, resolution of pictures in previous messages is not enough ? Not sure I can upload greater resolution (size). Do you have sprint layout software ?
 

Guga Ramone

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Actually I haven't seen those images before. Sorry for that.

I never used a sprint layout software before. Maybe I should've asked for the files used for creating the board instead of the images? Anyway I just want to be prepared for the moment my 8080 is beyond repair so I can install a new board on the amp.

Thanks!
 
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Hi, Thx for your message. IC1 protection is something that was missing on valvestate very first series. MARSHALL implemented it when they did the new generation, and for example this is what is present on a MG10CD:
View attachment 78874
So you can probably wire this way for 8080/8100 series :
View attachment 78875
You can find +15V/-15V in various locations on the board, I used R64 and R65.

I'm wanting to do this to my 8100 and I'm just comparing the diagram to the under the board wiring saunatonttu did. (I'm not great with circuit diagrams at all.)

So the polarities should look like this when tacking this protection circuit on the back? 20210108_070010.jpg
Also I'm guessing R2 and C1 are both going to Pin 5 on IC1 and that's why the Diodes are going to them?
 
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Ryan Powell

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Final PCB design just below:
View attachment 80086
View attachment 80087
Last changes I made is replacing solder connection of wires with male terminals 6.35 mm (similar to newer amps):

View attachment 80088

More convenient if having to work on the PCB.

Here's a picture of my beta board (ie not including all modifications):
View attachment 80089 View attachment 80090


Wow!!! Is there a way to get a replacement board? I have a ton of lifting traces, solder pads falling off or missing and its almost 20 percent of the board. Too many other "techs" got in guts of my amp with what looks like they used a branding Iron for repairs HAHA!! Just curious if its possible as it looks great!
 

Saunatonttu

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I'm wanting to do this to my 8100 and I'm just comparing the diagram to the under the board wiring saunatonttu did. (I'm not great with circuit diagrams at all.)
So the polarities should look like this when tacking this protection circuit on the back?
Also I'm guessing R2 and C1 are both going to Pin 5 on IC1 and that's why the Diodes are going to them?
I don´t remember which way they went and now they are in shrink tube so cannot confirm. The diode has only two ends, so connect them to the points according to the diagram Bobby provided, one end at a time. It´ll be good. I used the suggested R2 -> R64 and C1 -> R65 because the diodes were long enough to reach them. The point was to just find good practical spots for soldering onto. That´s why I chose the R2 and C1. Electrically speaking they indeed are the same spot with IC1 pin 5 and both have "something to hold on to".

Since then I have swapped the power switch (40€) that failed and put cable shoes to power- and transformer leads for easier board removal. Also had to replace "white1" transformer lead as it got too short in the process. Now going to get a new footswitch jack as the old is intermittent, and thinking about putting a molex or something for the reverb-leads for the same reason. Does anyone have suggestions for a good connector, or conversely, what to avoid for this (reverb) purpose? Not a fan of screw connectors.
 
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JR Abella

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I'll let you know when I place the order. Autotransformer is known as T5899 or T589 or METXVSHV.......
I am 99% sure that the auto-transformer in my 8080 is damaged, but to be 100% sure, and before I buy a new one, could you do me a favor ?: Please, measure coils ohms and tell me the result. Thank you.
 

Robert Herndon Project

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Hi,

This thread just to get a few advices from Marshall 8080/8100 users/modders/tweakers.

I have 2 amps, 1 x 8100 head, and 1 x 8080 combo version (12" speaker). I am attached to these amps as I have had them for a long time now, starting learning guitar with and like their overall sound.

But they are not perfect as you know, and weakest link is probably their PCB quality. I started facing difficulties to unsolder/solder components, getting fried soldering pads, also suspecting a conductive board in some areas making troubleshooting difficult... This JMP59/PC0689 PCB board, common to both amps, is corresponding to 90's standards when it comes to PCB production...

Not many options for me here as main fixes you use to repair trace is quite temporary, and a standalone PCB is not available unfortunately, so I had to go the difficult way and replicate this PCB on my own. Hopefully I owe decent equipment to unsolder components, and a lot of free time.

In the process, I torn down all components, removed the steel potentiometers bracket, heatsink, reverb connectors,... so that I could scan the board with high resolution and work on this in sprint layout software. This was tight as software is limited to 500mm in board length, so I managed to reduce current board length.

Here is the list of improvements I did on initial design:
1) use of a double sided PCB to integrate all links as part of top face with via holes (removes risk of bad links and reduces soldering time)
2) add a ground plan to each side as they were missing on initial design
3) add wire onboard connectors for reverb essentially (for maintenance and removal of board)
4) modification of TR8 and TR10 package to accept new generation transistors TIP 141 142 147... that have a different package (BDV64 and BDV65 are obsolete, but easily replaceable by TIPXXX)
5) indicate components values directly on the board (silk mask) for easy replacement
6) integrate a simple diode protection circuit for IC1 (very sensitive to static electricity and not that well protected on current design) on pin 5

My question is : would you see any mandatory improvements I should make before moving forward ?

Thanks for the hints.

Here are lowres top and bottom view of the board :
View attachment 78867
View attachment 78868

Wow, great work!
 


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