Please read this analogy as an educational comparison:
If you took your car to a mechanic, and you found out he never tested anything , but rather randomly replaced parts, you'd be very mad, right?
So what we're gonna do is use a simple trick for testing the reverb signal path.
If you were really on top of things, you'd have a little audio signal generator that put out a low sine wave and was isolated by a cap from a probe. You could then take that probe, touch it to a signal point in the amp (with no guitar plugged in) and listen to the speaker for an output. If you heard the tone from the speaker, everything after the point you're touching the probe to is functioning.
What we'd like to do is test the reverb chain for function, starting at its output and working back to its input. So you probably don't have the handy tone generator (I don't either; I have oscillators, but need to fashion up a probe). Take a small screwdriver with an insulated handle, like an Xcelite or plastic-handled jewler's screwdriver. If you touch a plate or grid pin on a tube socket with this screwdriver, you will hear a thunk through the speaker. You want a small screwdriver so you don't acidentally short a pin to another or to ground, and you need an insulated handle to avoid a hair-raising experience.
Start at the end of the reverb chain, where the signal gets mixed back into the dry signal. Touch a signal point, then repeat at an earlier point. I habitually start with the plate of the last tube stage involved, then if I hear a thunk, I move to the grid of that tube and expect to hear a louder thunk (amplification, right). I keep working backwards like that from the output, plate, grid, earlier plate, earlier grid, until I find the point where signal is not being passed. Then I stop and figure out if it is a tube issue (are power supply voltages good? Is the tube making good contact in the socket? is the tube working at all?) or if it is a component or wiring issue. You fix things in that area, then continue to work backwards to the input of that chain; when you get there, everything is working properly.
So you might have ruled out the reverb pan and reverb transformer. It's not ideal, but if you can bang the cabinet and hear the reverb crashing, then everything is good from the output of the pan back to the rest of the amp circuit. But you should be able to touch the scredriver to the pan input (maybe at the send jack) and hear some noise. The point at this jack is safe for you to touch your finger to the screwdriver and try to cause it to buzz. If it doesn't, then you have to wonder about the cable or jack wiring. If it does work, then continue with testing at the reverb driver tube (feeding the reverb transformer).
If you work backwards, you will certainly find the spot where you go from signal to no signal, and then you just have to figure out why no signal at that spot.
Topic: Bandmaster Reverb...AAAaaarrrrrrgggghhhhh!!!!!! (Read 4703 times)