Modding a small practice amp - pots, switches etc.

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First time poster and rookie tinkerer here, so apologies for any noob questions, breaches of etiquette, general stupidity etc.

I have a cheap early 90s solid state practice amp (made in Korea by Acrobat, apparently) which I'd like to try and upgrade, really just for the hell of it. I'm curious to see if a decent sound can be got out of it and even whether it could be made giggable in a small bar type environment.

The main things I'm doing are to replace all the pots (some of which are broken and probably not great quality to start with) and upgrade the massive 5" speaker to something more substantial. I'd also like to add some switches for overdrive and reverb.

Common to amps of this size, it's single channel but has an overdrive pot. What would be cool would be if I could set the overdrive to the desired level, then switch it in or out at will. I understand that if I just put a switch over the pot, it would let me switch between full distortion and a level set by the pot, which isn't what I'm after - I want to switch from a level set by the pot to clean.

The pot is labelled as 1 meg. Is there such a thing as a push-pull pot that would switch to maximum resistance (ie clean signal, presumably) when pulled out, then function as normal when pushed in? Or if not, is there some way I could put a 1meg resistor either on a push-pull pot, or a separate switch, to perform the same function?

Any advice would be greatly appreciated. In the fullness of time I'd also like to add a footswitch, but first things first eh...
 
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Here's the present overdrive pot itself (on the left).
 
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....Could use some guidance on the pot/switch issue!
Without a schematic circuit diagram, you would need to carefully re-draft the relevant circuitry from the PCB before it can be certain what you have there and what advice to give.

These are usually anonymously branded products that have always been difficult to get service details and schematics for. Some members here have no problem with tracing the circuit from the PCB but it requires high res. images, top and bottom side of the board to do this via the 'net. It's not a simple 5 minute task unless you know what to expect in the first place. I would think that the guys in the Instruments and Amps forum would be more helpful sourcing a schematic and offering specific advice for guitar amps generally.
Instruments and Amps - diyAudio
 
Haha, I'm afraid there's not much chance of a schematic - way beyond my capabilities, and the internet won't even admit the brand exists let alone its innards!

Will give Instruments and Amps a try. In very general terms, does switch + resistor sound like a plausible way to bypass the pot when required?
 
Probably not. The gain controls in these things is usually part of the op amp feedback loop in the stage.

perhaps you could replace the overdrive pot with one of the same value with a pull switch, then have the switch put a resistor in place of the pot. The resistor value chosen to be the same as the OD pot in the clean position.

But then you'd have to have room for such a pot on the panel.
 
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