Spring reverb?

It may be a reverb driver problem.

The way the reverb functions is that there is a small power amp that drives the signal into the tank. The tank then delays the signal and sends it into the output section of the amp.

A simple test of the send section is to disconnect the tank input wire and connect it to a speaker. Turn the reverb up and see if you get some sound from the speaker. You already tested the return section effectively by listening to the sprong.

If both the driver and return work, it must be the tank. They're cheep and available at tubesandmore.com

 

A broken wire right at the input or output jack on the tank is pretty common, and only a moderately difficult DIY fix. If the break's at the transducer end just replacing the tank is the call unless you're a real masochist. A fried opamp on either the send or receive side is quite possible too; that is a fairly technical repair unless it happens to be socketed. None of these takes all that much bench time for a decent tech. Occasionally the reverb switching circuit is at fault, have to know more details to comment on that possibility though.

Are you sure you care enough about using the 'verb for a bass application to bother fixing it in the first place?

 

I use my Flint quite a lot with my basses. Of course, it sounds way better than any sprinnnnnnnnnng reverb.

 

I use digital 'verb quite a lot in my own band, but the typical Peavey sproinger in many of their SS amps wouldn't be worth throwing much money at to me for a bass application. I could almost always fix 'em without having to do that though.

 

Can't be the reverb driver if there's no return signal. It's probably going to be either the receive transducer, receive wiring, or return amp.