Randall RG80 112 SC

[bojac]

I picked up this amp recently at a garage sale. The foot switch came with it. The Hi side works fine but the Lo side don't work at all. Is this an easy fix? How to go about it? I would like to get it up to snuff for a partial trade on a pv classic 50.

[JHow]

I picked up this amp recently at a garage sale. The foot switch came with it. The Hi side works fine but the Lo side don't work at all. Is this an easy fix? How to go about it? I would like to get it up to snuff for a partial trade on a pv classic 50.

Are you saying that just the "Lo" jack doesn't work, but you can switch between channels? That should should be something fairly simple, there's only a jack a wire and a 68K resistor difference between the Hi and the Lo. I would suspect loose/broken wire/jack, something mechanical.

If one channel works and the other doesn't, then it may be more of an issue.

[oc disorder]

According to the schematic if (as JHow says) its just the lo jack that doesn't work the repair should be easy.
The Tip of the input jack on both sockets goes through a 68K resistor (ie Blue Grey Orange) which then join to go to the circuit.
The Hi jack also uses the switch section of the jack to connect its 68k resistor to ground when there is no plug inserted.
This is typical of lots of amps. If you follow the path from the tip of the lo jack you should see it goes through the 68K to the other 68k from the hi jack.

[bojac]

Are you saying that just the "Lo" jack doesn't work, but you can switch between channels? That should should be something fairly simple, there's only a jack a wire and a 68K resistor difference between the Hi and the Lo. I would suspect loose/broken wire/jack, something mechanical.

If one channel works and the other doesn't, then it may be more of an issue.

Yes JHow I can switch channels on the low side, but no sound. I'll check out that jack assembly. Thanks for taking the time to respond guys. I do appreciate it. Thanks for posting the schematic oc disorder. I'll post what I found.

[bojac]

Maybe I opened a can of worms. I see 3 screws on each end of the power head under the top of the box with a strip of wood blocking these screws. So what is the trick to remove the head? Or do the knobs and nuts come off to remove the panel strip to get at the lo jack? As you may have guessed, I'm not an amp tech, and I'm not wanting to tear things up.

[bojac]

I figured out how to get the head off. Just too easy. And the problem was the white jack wire is off of the 68k resister. Now to get some solder and a smaller soldering gun. Thanks so much JHow and oc disorder! Great forum by the way.