Fender 65 Twin Reverb Deluxe - Vibrato Input DEAD.... :\

[Fenderman]

Hi all!
The Vibrato input (both 1&2) of my amp is dead.
I purchased a new footswitch, new reverb tank, replaced in all combinations, changed the cable from the amp plugs to the reverb tank but nothing helps...
There is no sound at all. Also, there are no "crashing" sounds when moving the reverb tank.
The only thing that can be heard, is when the reverb is ON (through the footswitch) - when I turn the reverb nob there is some very slight hashing. That's it...

Any idea will be much appreciated !

Plating flat, dry sounds for now!

Thanks guys

[pdf64]

Have you tried swapping in your 'known good' tubes?
If not give it a go, but if you don't have any spares then try swapping the tubes that are in V1 and V4 slots around.

[Fenderman]

Thanks!!
Could you please direct me which ones are the V1 and V4?

[52 Bill]

Could you please direct me which ones are the V1 and V4?

Looking from the back of the amp the rightmost tube is V1 and V4 is the fourth one from the right.

[Fenderman]

Looking from the back of the amp the rightmost tube is V1 and V4 is the fourth one from the right.

Thanks man! Tried this but it didnt work..... any new ideas will be more than welcome. My wife is begging for some vibrato..... 😃😃😃i'm talking about music of course.

[52 Bill]

Thanks man! Tried this but it didnt work.....

Try swapping V1 and V2.

[gnappi]

I have to ask, do you have a schematic, a rudimentary base level understanding on reading them and a DMM? If not beyond the next line there's little you can do.

Beside V1 and V2 and V4 the volume pot can cause it, my Super Reverb Vibrato channel volume pot went to 10 everywhere on the dial and after flushing it's fine.

[gnappi]

I've looked at the schematic, and if V4 is OK then you may have a separate issue with the reverb. If so I'd start looking at the coupling caps before V4.

[Richard]

If there is no sound on the vibrato channel and there is no handling noise from the tank then V4 seems to be the likely culprit. It's not common for two problems to happen at the same time so I would focus on the area around V4B as that is where dry signal from vibrato channel and . The reverb should be on when the footswitch is unplugged so I would leave that out for now. The wet and dry signal goes through V4B. Are you comfortable poking around inside tube amps? There are very high voltages (+442 according to the schematic) present, and they may remain even after the amp is unplugged!

I would suggest unplugging the amp, removing the chassis, place the cabinet face down and rest the chassis on the cleats that run up the back of the cabinet. (make sure your tubes are not hitting the backs of the speakers) Plug in the speakers and turn the amp on, take off standby when ready. If you touch a probe to pin 7 of V4 you should hear something through the speakers. Based on what you describe I don't think that will happen. Since the clean channel works we can be confident that the phase inverter and power amp are in good shape. To oversimplify: a tube needs signal (pins 2 and 7), grounded cathode (pins 3 and 8), plate voltage (pins 1 and 6), and output (a coupling capacitor connected to the plate (pin 1 and 6). If you have replaced V4 with a known good tube and your problem still exists then examining this area is our best bet.

[g1]

To oversimplify: a tube needs signal (pins 2 and 7), grounded cathode (pins 3 and 8), plate voltage (pins 1 and 6), and output (a coupling capacitor connected to the plate (pin 1 and 6). If you have replaced V4 with a known good tube and your problem still exists then examining this area is our best bet.

And it must have heaters. Lack of heater voltage is something that could stop both A and B sides of V4 from working.