That.

Enzo used to strip knobs, fuse holder caps, maybe a handle or corner protector, a speaker, which might prove useful later.

Sometimes even a Power transformer.

Quote from: anderson4584 on July 10, 2025, 10:56:55 AMI can always change to channel 3. But I have issues getting it back to channels 1/2. I opened up the footswitch and everything seems fine in there. I played with the wires a little bit to see if it would change anything and the only thing that changed anything is.......it typically works fine when I hold the footswitch upside down.

That makes no sense.
Do you hold pedal in your hand or put in on the floor? (so floor can push both buttons at the same time)

 

QuoteWhen this issue happens, I also typically lose a lot of power output while playing, but ONLY in the bridge pickup. If I switch to the neck pickup, I get power back. That makes even less sense..

-

QuoteTried using another 2 switch footswitch I have that goes to a Peavey classic 20MH (this works... but it ends up having the same issue, which leads me to believe it's the amp).
-Swapped some cables around, and tried different guitars.

For testing, plug a spare TRS/"stereo" plug in theb Fsw jack.
Cover open, pins visible.

Solder a short (1" to 2") piece of wire to plug ground terminal.

Then touch either of free pins (to simulate temporary switch) with the free end ... what happens?

Repeat test but now soldering wire end to a pin or another to simulate a latching switch.

This way you are testing using a bare minimum "pedal equivalent" device, very simple and easy to understand, which depends on nothing else.

Post results.

Any ideas?

Just the button or the full switch?
Post a switch picture.

CE distribution in Arizona usually has all parts Fender, even some not available from Factory any more

https://www.cedist.com/

What is the problem you are trying to solve?                                                                                                       

Quote from: dmeek on July 07, 2025, 10:48:25 PMHere is the preamp schematic. The Tone switch is a gyrator notch filter. I can't see the value of the silver capacitor on the tone board but if
I assume it is 1000PF the frequencies are: 1 - Flat, 2 - 230Hz, 3 - 1kHz, 4 - 3.4kHz. If you can read the value, let me know.
I couldn't draw the reverb section because the foil side is hidden by the footswitch jack. If you can move it and post a photo I can do it.
If you want to lift the power board and post a photo of the foil side I can do that too.

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Thanks Dmeek, incredible job, as usual.

What I find *weird* is that the exact same amp (differences are just "modernization" but design/ideas are the same) was made "on both sides of "the Curtain/Wall"" because Regent maker was an East German/DDR State run Factory.
So much so that components used are "Soviet Block" type.
Transistors are Tesla, made in Czekoslovakia, guess other components too.

Not sure where did "the Reds" get Reverb tanks, for example.

Also curious about what speakers were fit in those amps.

My point is that *maybe* East Germans copied a British amp (although an earlier discrete transistor version), the opposite sounds unlikely.
But the Londoner uses American transistors (RCA) and ICs (Texas Instruments) but Britiish Cliff jacks and capacitors.
No brand visible but those large Blue ones look same (or very similar) to those used by Marshall.

Mysteries of International trade.

Sounds like state of the art troubleshooting to me 

Quote from: blackcorvo on July 02, 2025, 03:47:59 AM

Quote from: Loudthud on July 01, 2025, 09:31:23 PMWell first thing you gotta know is what power supplies are available to run the preamp ?

Initially, I'm thinking just 12v, both for the power amp and preamp, as I already have a 12v PSU that works well with the amp, and I could easily add a 3x 18650 battery holder to it in the future.
I also have some XL6009 boost converters, so I could use one for higher voltages on the preamp if needed.
The TDA8932B board I have can work with up to 30v, but I'd probably limit it to 20v max just for the sake of not going over the speaker's max 30w rating.

Marshall Lead 12 is a KILLER little SS amp.
You can build just the preamp to drive your power amp.

Full schematic

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Preamp only:

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2 "problems" to solve:

1) you will have to draw your own PCB
There are a couple ones on the Net, also Veroboard versions, but I do not trust them.
Also designers get "creative" and add unnecessary features as diode clipping, switchable gain stages, different EQ, etc. which actually degrade it.
Best is original one which is also the simplest.

2) it needs symmetrical supplies.
Originally +/-16V but works fine with +/-12V
You already have +12V and it is easy to get -12V out of it, using a charge pump IC.
I´ve done that many times for my 12V Lead Acid battery powered "Callejero" (Street Musician) busking amps.
Didn´t even use a charge pump IC (not available way back then in Argentina) but a humble 555 oscillator, go figure.

3) Plan B: most any Distortion pedal can work as a preamp for your Chipamp, even a humble MXR Distortion + , a Tube Screamer, etc. and all those work straight from single +9V supplies, and are happy with +12V.
Or you can pad +12V down to +9V by using an LM7809.

To broaden the scope: there are a few "Amp in a Box" pedals, sporting full tone controls, search the usual "PCB Pedal" sites.
But read all comments and build only those which are "checked".
Marshall Guv´nor is a Marshall preamp channel in a pedal format, works out of single +9V and there is a tested iron-on PCB layout available. search for it.

Don´t you have a pedalboard? Or a Zoom (or similar) pedal?

Those can straight drive your chipamp.

What a complex power supply 

It scratches my minimalist brain quite the wrong way.

Oh well.

Start by measuring reverb rank coils DC resistance at both ends.
I would expect in the order of 50-100 ohms at the output and 5-20 ohms at the inputy.
That would be DC resistance, impedance is some 10X higher. 

IF one is open, look inside, often thin connecting wires break , the spring cradle itself is spring mounted and shakes a lot.

I also went through the methods above.
I guess we old timers went through the methods popular at each "era".

 

Looking at Tassieviking´s schematic, I was impressed by finding a "modern" amp.

I half expected that an amp made by a State run East German Kombinat (Socialist style Factory) would be very boring old school but no, the design holds its own.

The pot adjustable "Parametric EQ" is actually a Wien Bridge based deep notch filter, where you can continuously select Frequency between 200 and 2000 Hz, a very useful range for Guitar, and a pot adjustable Depth, from flat to -20dB

The 4 position rotary switch version probably selects 4 from the many possible sounds.
Not bad at all.

You can mimic the EQ of various "famous" amps, say Fender Tweed/blackface/silverface or Marshall or VOX 
Very clever.

Exact same here 

Thanks Tassie 

Quote from: Dwknjh6 on June 21, 2025, 05:58:52 PMI probably should've been a little more clear on the amp, yes it powers up and produces sound. Input 1 doesn't work at all and is actually loose on the board, hoping it's just broken solder joints. I put 2 barely works, but is scratchy, hisses and pops, looses contact pretty easy. Every pots dial was horrible and did the same thing, and the overdrive button was the same. Honestly it's impossible  I did wonder if maybe at first I just replace the filter caps. As they are 26 years old.
 I really didn't want to have to pull the board multiple times I guess is the main reason I had for going ahead and replacing all the caps. When I'm finished I'll be selling the amp.

Nothing to replace unless it spewed its guts out or is smoking, those caps are fine.

Repair it for your own use, or donate it (working) to a School or Church, it is NOT a "business".

That is a killer amp, Celestion 100 speaker is a beast, but if you want to keep cost down any "good family" Guitar speaker, meaning a Craigslist/garage sale $15/20 (tops) speaker will work fine.

I mean a house brand "pull" from Fender/Crate/Peavey/etc. which 90% of the time is an OEM Eminence, only with a fresh "brand" sticker, such as blue Fender Special design, Randall Jaguar, whatever Carvin Acoustic Laney Ampeg etc. use.
Lots of preople replace Factory speaker by an "improved" Celestion or Eminence, and have no use for the old one, so sell it for peanuts.

You can use an 8 ohm speaker there, only reducing power from 90W to still very loud 50W or so.

With my half cooked workaround, you can do that (literally "rip and reroute") with tape, which is the most complex partb of thejob.

You would be stuck with drawn or permanently glued pads though.

There is a so called Tolex Glue which is water based.

It remains tacky when dry, for a long time (many days at least), it works as a permanent contact cement only if you apply it to both surfaces, even so not *that* permanent, British amps are cabinets (Marshall, Laney) are (in)famous because cabinet wrapped in back edges often get loose, and have to be reglued.

IF used on a single surface you can stick and pull it from a non porous surface, such as drawing Mylar, then reattach elsewhere.

I have used it to attach acrylic or thin aluminum front panels (think Marshall Plexi or golden aluminum sheet) to punched amp chassis.

Not saying you buy a bottle for testing but IF you re Tolex a cabinet using it, you might try some leftover to check it.