Epiphone Valve Standard to 18W TMB Conversion

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michel
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Post by michel »

Hi,

Like I said I am a newbie. I posted some pics on this thread:

http://www.ppwatt.com/node/15351

I am pretty sure though I can follow the trace from the R17 to the VR6 outer leg...

I took some pics showing the different numbers on the PCB...

http://www.ppwatt.com/files/ppwatt/vr6.jpg
http://www.ppwatt.com/files/ppwatt/r17.jpg

I have a pic of the trace also in attachment...

Since I don't konw what I am doing, I must rely on a schematic, but PCB does not seem to know it... ;-)

Thanks,

Michel
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cGil
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Post by cGil »

bigjoe wrote:THe easiest way to get rid of the DSP is to pull the PCB and throw it in the trash.
My sentiments, exactly. I tried to warn 'em.
bigjoe wrote: Mine says HB01574 - VER050305...
Mine, too! My board was hiding under the bench, but I dug it out for this occasion. This one was a modded mess when I got it. Lots of post-factory resistor and cap additions and jumper changes not consistent with the schemo at all, but that seems to be par for the course.

After reading this thread and then finally seeing it up close for myself, I understood immediately why there's not much hope for this thing. Too messy, and far too flexible a board to last very long no matter what you try to do. I stripped mine of anything really useful within hours of getting it home, but then, I bought this amp just to rebuild it from scratch anyway.

Gil...
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michel
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Post by michel »

cGil wrote: Mine, too! My board was hiding under the bench, but I dug it out for this occasion. This one was a modded mess when I got it. Lots of post-factory resistor and cap additions and jumper changes not consistent with the schemo at all, but that seems to be par for the course.
So, you never worked with an original Valve Special. That must explain the difference between your description and my board.

Will keep looking...
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cGil
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Post by cGil »

What? Stripping my Valve Standard wasn't work? I beg to differ! :)

And seeing pictures of your Valve Special board and comparing it to the same exact traces on mine tells me you really should quit whining about insignificant minor molehills and simply follow the footsteps you've found in here. The fact that you're here says you've found all the information you need. What more do you want?

Gil...
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bigjoe
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Post by bigjoe »

look at the other side of the board on your trace pic. I'm certain that on mine R17 didn't have a direct route to VR6. It took me a while to figure it out. I was convinced at one point they did have a direct route. The reults I got said different.

My board is stripped clean of any factory wiring so I'm at a disadvantage. I might suggest you pull the components legs that I suggested and run the wire from R17 to VR6. Mine seemed to have a lot of post automated production mods also.
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JCM-800
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Post by JCM-800 »

I have been studying this thread carefully.

I've replaced the bias resistor with a diff value someone from another site suggested (and even sold me the part) as it would crap out running full bore, and this helped alot (still cuts out on occasion)

I also just removed the DSP board, but am still having problems with a farty/crackly noise when the gain is up all the way and the master is around 2/3s. When it crackles, the DSP LED actually flickers...?

Any ideas on that?

Plan to put some JJ EL84's in and get a V30 for it. Would like to try alot of the other mods listed for fun.
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zaphod_phil
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Post by zaphod_phil »

Crackliness with the flickering LED suggests a bad joint, loose connector or damaged PCB track somewhere, when the louder playing vibrates the board more.
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lapslide
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Epiphone Valve Standard modifications

Post by lapslide »

Hello all,
Has anyone done up a final version of the modifications for the Epi Valve Standard that are known to work, i.e gone through all of these posts to gather the relevant circuit changes and produced a clean guide?
I've grabbed what I think are final versions and notes, will print out and go through them to see if I can reduce it to one set - but would prefer not to reinvent the wheel, so to speak.

Cheers,
Donn in BC
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bigjoe
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Post by bigjoe »

At some point the board went down, and I wasn't sure if it would be back up. I didn't have e-mail for anyone, so I pulled the PCB and built an 18 watt board for my EPI.

Not much help I know, but I didn't really do anything with the EPI specific mods myself.
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dthill
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Post by dthill »

I'd be interested inn the same thing for Epi Valve Special.

Though, I guess I could use it for a 18watter...........

dth 8)
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Post by zaphod_phil »

lapslide wrote:Has anyone done up a final version of the modifications for the Epi Valve Standard that are known to work, i.e gone through all of these posts to gather the relevant circuit changes and produced a clean guide?
What's in the thread is all that we've got. There's a similar thread on PPwatt.com, since the discussion took place around the time that 18watt.com spawned off PPwatt, SEwatt and the other wattkin sites. I think that thread has a summary of the mods to convert the Valve Standard into a single-channel 18W TMB amp. However, the thing to be real careful of is not to break the PCB. 8O It's pretty thin.
dthill wrote:I'd be interested inn the same thing for Epi Valve Special.

Though, I guess I could use it for a 18watter...........
IIRC is a single-ended amp, kind of like the Valve Standard's preamp with the Valve Jr's 5W power amp. If so, there's a similar thread on SEwatt.com, again from around the same time period, for that amp. Of course if you wanted to gut it out and put in an 18W SuperLite TMB board say, that would be fine as well, although you would also need to change at least one of the transformers.
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CudBucket
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Re: Epiphone Valve Standard to 18W TMB Conversion

Post by CudBucket »

Hey all. Late to the party as usual. :)

A friend just gave me a "non-working" valve standard combo. No speaker in it. Thought I'd take a crack at fixing it. I've tested nothing so far. I've just begun researching the amp and found this thread.

A few years ago I bought a Marshall JCM 2000 DSL and learned a ton as I fixed the bias drift issue and did a few mods. So I'm not really a noob.

After reading this thread I'm pretty sure it might make more sense to just use the chassis and cabinet as a platform for an 18 watt build. So that said, where should I look for the parts? Is there an 18 watt kit?

As for the amp in it's present condition, everything looks fine apart from what looks like a burned disc cap on T6 that is wire to the heater quick connect. Not in the schematic as far as I can tell. No burns on the boards anywhere. Fuses are good and everything is really clean.

Anyway, I'll post pics later but I'm torn between the new build and fixing this first. Then, maybe doing some mods.

Thoughts?

PS BigJoe, where did you get your 18 watt TMB?

Thanks again.

Dave
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