Hi!
My first post in this forum.
I recently bought a Super PA 100w from 1970, model 1968.
It was in need for service.
I have done the following things to it:
- Tested tubes (all in good shape and bias adjusted to 38mA)
- Cleaned all sockets and inputs
- Cleaned all potentiometers
- Replaced all filter caps, both cans and those on turret board.
- Resoldered loose ground joints.
It went from really bad to 95% good! There are two things that bother me.
- Input II and IV is not working (there is a minimal sound coming through if i strum the guitar really hard. I replaced two jacks with no luck.
- There is some hum left, it gets worse if i turn volume up or adjust treble / mid up. The ground bus on the potentiometers look quiet thin. What should i do?
If i remove preamp tube 1 or PI it is gone.
Cheers!
My first post in this forum.
I recently bought a Super PA 100w from 1970, model 1968.
It was in need for service.
I have done the following things to it:
- Tested tubes (all in good shape and bias adjusted to 38mA)
- Cleaned all sockets and inputs
- Cleaned all potentiometers
- Replaced all filter caps, both cans and those on turret board.
- Resoldered loose ground joints.
It went from really bad to 95% good! There are two things that bother me.
- Input II and IV is not working (there is a minimal sound coming through if i strum the guitar really hard. I replaced two jacks with no luck.
- There is some hum left, it gets worse if i turn volume up or adjust treble / mid up. The ground bus on the potentiometers look quiet thin. What should i do?
If i remove preamp tube 1 or PI it is gone.
Cheers!