Bass Potentiometer ?

[gtrplayr1976]

Is the footswitch plugged in?
If so, try unplugging it.
Pete

Yes Pete the footswitch was plugged in. Seems that's the only way I could get the reverb ,and tremolo to come on. FYI: someone had changed the wire on the footswitch to some 4 conductor flat cable. Don't know if this would cause an issue with noise ,or otherwise.

[gtrplayr1976]

Is the footswitch plugged in?
If so, try unplugging it.
Pete

Pete I unplugged the footswitch ,and there is no hum. Would that mean the footswitch is the issue ,or something at the input of the switch?

[pdf64]

The cable to the reverb footswitch must be screened, otherwise hummmmm.
Same as an instrument cable.
But do you really need to switch the reverb on/off?
If not just don't plug anything into the footswitch RCA on the back panel.
Pete

[gtrplayr1976]

The cable to the reverb footswitch must be screened, otherwise hummmmm.
Same as an instrument cable.

By screened I assume you mean shielded ? If it were my amp I wouldn't worry about it. It would probably be as cheap to buy a new switch than to replace the cables. The flat cable they used has one hot ,and one ground for each plug ,but it's more like speaker cable.

[Jazz P Bass]

The Fender stock cable was 2 conductor with a braid on the outside.
The braid was used as a common.

[gtrplayr1976]

The Fender stock cable was 2 conductor with a braid on the outside.
The braid was used as a common.

The braid was only used on one of the conductors ?

[Jazz P Bass]

Sorry, the braid was the common conductor to ground.

[Enzo]

The Fender cable was one wire with braid shield around it plus a second plain insulated wire outside the shield. The shield served as the common ground for both switches.

The reverb cable must be grounded because it is in the signal path. The output of the reverb pan plugs into a jack on the amp, and the reverb FS jack is wired to it. The signal wire runs out to the FS. To turn off the reverb, all we do is short the reverb output to ground through teh switch. If the wire is not shielded, then it acts like a big hum antenna.

[52 Bill]

The original cable was a single center conductor shielded cable and a separate white wire that were covered in a heat shrink tube.

The reverb line carries audio, so it must be shielded.

The trem is just the oscillator ground connection so it does not need to be shielded, but it does need to be grounded to turn on the trem oscillator.

[gtrplayr1976]

Sorry. We had a death in the family last week ,and I was unable to get back to this.
OK...so it seems whomever rewired this footswitch wired it wrong. They used four conductor flat cable with both sides grounded. Maybe it would work if I disconnected the ground from the tremolo side ?

[52 Bill]

Sorry. We had a death in the family last week ,and I was unable to get back to this.
OK...so it seems whomever rewired this footswitch wired it wrong. They used four conductor flat cable with both sides grounded. Maybe it would work if I disconnected the ground from the tremolo side ?

Sorry to hear about your loss.

Is the cable shielded in any way or not? If you pull out the reverb rca plug does the trem still turn on and off?

The wire that goes out to the reverb switch is carrying audio signal. If the wire is not shielded, it will pick up noise and hum which will be added to the audio signal. If the 4 conductor flat cable is not shielded, it needs to be replaced to kill the hum in the reverb signal.

[gtrplayr1976]

Sorry to hear about your loss.

Is the cable shielded in any way or not? If you pull out the reverb rca plug does the trem still turn on and off?

The wire that goes out to the reverb switch is carrying audio signal. If the wire is not shielded, it will pick up noise and hum which will be added to the audio signal. If the 4 conductor flat cable is not shielded, it needs to be replaced to kill the hum in the reverb signal.

They used one wire for conductor ,and the other for ground on both plugs. With the switch unplugged there is no noise,and the reverb sounds fine. The tremolo doesn't work without the switch correct ? I haven't tried disconnecting the reverb plug only.

[gtrplayr1976]

Is the cable shielded in any way or not? If you pull out the reverb rca plug does the trem still turn on and off?

The wire that goes out to the reverb switch is carrying audio signal. If the wire is not shielded, it will pick up noise and hum which will be added to the audio signal. If the 4 conductor flat cable is not shielded, it needs to be replaced to kill the hum in the reverb signal.

This is a shot of the cable ends. You can see the type cable that was used.

[52 Bill]

This is a shot of the cable ends. You can see the type cable that was used.

That appears to be double speaker wire, definitely not shielded.

The reverb wire must be just like a guitar cable or just like the cables that go to the reverb tank itself, a single wire surrounded by a braided (or otherwise shielded) outer covering.

[gtrplayr1976]

That appears to be double speaker wire, definitely not shielded.

The reverb wire must be just like a guitar cable or just like the cables that go to the reverb tank itself, a single wire surrounded by a braided (or otherwise shielded) outer covering.

It IS basically speaker wire. I've seen pictures of the original ones. I bet that's what's causing the hum as you ,Jazz ,and Enzo have said.