Reverb squealing in Fender Super Reverb

[mageerc]

I've been working on a 1966 Fender Super Reverb. I have changed all the electrolytic capacitors. When I brought up the amp, it sounded great until I turned on the reverb. There is no reverb signal and the amp starts to have more hum and about halfway up on the reverb knob it starts a very annoying squeal. I cleaned all the tube sockets and changed both the driver and recovery tubes out with known good tubes. I'm getting resistance out of both the input and output sides of the reverb tank. I'm a bit stymied as to where to go from here.

[pdf64]

A bad cathode bypass cap on V4 can cause squeal.
But not loss of signal.
But there may be different, coincidental issues.

[eggbert]

You check the wires to and from the pot, and shielding on them, had this happen before to me. Also the tank connection where rca;s plug in?  Are they plugged in right spot, and had a bad tank that measured ok, yet it squealed, resistance thru the wires from amp to tank.  Just a few of my issues. Maybe you already did these things.

Good luck

[tubeswell]

I've been working on a 1966 Fender Super Reverb. I have changed all the electrolytic capacitors. When I brought up the amp, it sounded great until I turned on the reverb. There is no reverb signal and the amp starts to have more hum and about halfway up on the reverb knob it starts a very annoying squeal. I cleaned all the tube sockets and changed both the driver and recovery tubes out with known good tubes. I'm getting resistance out of both the input and output sides of the reverb tank. I'm a bit stymied as to where to go from here.

It could be your 12AT7 driver tube is bad or no cathode connection, or the RT ist kaputt, or the 'to-pan' cable is bad or the pan's input transducer is bad.

Or the 'no reverb' could be a bad 'from pan' cable and the squealing could be a microphonic recovery tube (hold the recovery tube and see it it dampens the squealing)

or the squealing could mean that the tube is okay and the pan's output transducer and send cable might be functioning okay  - and the squealing could just be reverb pan feedback (one way to find out is put your thumb on the back of the pan and see if the squealing stops.)

[mageerc]

Turns out it was a bad cable that the shielding failed... thanks for the suggestions guys!

[DummyLoad]

Turns out it was a bad cable that the shielding failed... thanks for the suggestions guys!

late to the party...

with regard to repair of a once working reverb ckt, cables, connectors, and tanks, in that order are always first suspects. of course, testing tubes is ruled out beforehand.


--pete

[eggbert]

Glad you got it.  I am still working on a ghost note in my super reverb, damn thing has me stumped?????