St George Massie 1263 Scratchy Sound

[oogabooga23]

Whenever I turn the volume knob on my guitar, there is a scratchy sound coming out of the amp. This only happens in 1 of the 4 inputs. I haven’t tested any leakage, but I am assuming it could be a bad capacitor?

[shooter]

I'd look for a bad connection, either at jack, sketchy solder on the jack, or parts connected to the jack

[sluckey]

schematic...

[shooter]

^^ thanks


I'll add C2 to the mix then

[sluckey]

Would be helpful to know which input.

[oogabooga23]

It was on input 2 above the tremolo, should of specified

[oogabooga23]

There also seems to be a problem with the tremolo circuit not working at all. I saw somewhere that they fixed the problem by replacing the 6CA4 rectifier tube, but I don't see how that would necessarily help. Changing the tremolo tube with a known good one did not help either.

[sluckey]

It was on input 2 above the tremolo, should of specified

What does that mean?

Look at the schematic I posted. There are 4 inputs labeled TREMOLO, GUITAR, BASS, and ACC. Which one is scratchy?

[oogabooga23]

It's the one labeled GUITAR, sorry about that

[shooter]

happens in 1 of the 4 inputs.

took that to mean the 1st of 4, then the schematic inferred Trem as the 1st of 4


I miss the days of reading error logs and diagnostic results 

[sluckey]

I miss the days of reading error logs and diagnostic results 

Yeah. We had better communications skills back then and the brain was not cloudy all day!   

[sluckey]

It's the one labeled GUITAR, sorry about that

Are you a tech and have a dmm? If so, plug a guitar cable into the guitar input but don't connect the other end to anything. Now measure dc volts between tip and sleeve of the dangling plug. What have you?

[oogabooga23]

I am no tech at all, but I do have a multimeter. I measured 0.9 volts DC in the GUITAR input, 0.5 volts DC in the BASS input, and 0.4 volts DC in the GUITAR/ACC input. For the TREMELO input, I kept getting a reading of 0 volts.

[oogabooga23]

It seems that the problem resolved itself after I removed the death capacitor when I was making a negative feedback switch. I don't know why I didn't remove it to begin with, even though I installed a 3-prong, and the ground switch was useless. With that resolved, I can start to figure out how to get the tremolo working, as the tube lights up but it does not make any sound.