Hum with Reverb Channel?

[mattnorthrop]

Hello! I have a question for all you techs that are way smarter than me:

I have a 70s Fender Super Reverb(with master volume) that has a peculiar habit. Whenever the reverb knob is turned past 2 or 3, this horribly loud hum/buzz occurs at a constantly loud volume regardless of the volume controls and regardless of whether a guitar is plugged in or not. Additionally, the reverb does not seem to be working at all. Anyhoo, I'm trying to figure out what's going on and whether this is something I can fix myself (i consider myself a beginner, although I have done some basic work with amps).

Anyways, thanks for any help you guys could provide.

Matt

[Mars Amp Repair]

Matt,.
I'd verify that the reverb unit has resistance on both coils. Measure from each jack on the reverb unit...input & output & look for resistances for input = a least 4-8ohms (some newer are higher...ok cause at this point you're just looking for some continuity).
On the output side, you will probably see about 220ohms...like I said the value is not as important at this point as the fact that there is conductance.
you could also have the plugs reversed...not usually a hum issue, tho. glen

[Enzo]

And unplug the foot switch if it is in.

Look at the cables from the pan where they plug in. The braided metal shield can fray. Is it intact and soldered to the plug shell?

[mattnorthrop]

Thanks you all so much for your help!

I have not measured the reverb input and output jacks (seeing as how my DMM has been misplaced), but I did completely disconnect the reverb unit from the amp to see if it there was any change. Unfortunately, there wasn't. With the reverb disconnected, the amp still hums horribly after turning the reverb knob to 7 or 8 (this is what it was doing with the reverb connected).

Would I be safe to say that I can rule the reverb unit out as the culprit? Does this thing just need a cap job?

Thanks again for ya'lls help!