iHatePop wrote:
To test the loop, couldn't I just run a cable from the Send to Return and see if they work?
That might work...I say might because it's a parallel loop. The level or blend pot controls how much of the loop signal is mixed with the dry signal to the output stage. With an effect, you can hear if the loop is working by whether or not you can hear the effect. With a jumper, you might not be able to tell if the loop is working because the "wet" or loop signal is identical to the dry signal. I suppose there might be a slight change in tone or volume, but I couldn't say for sure. I doubt it would hurt to try.
The jumper test would work on a serial loop, because if there were no continuity through the loop, you'd get no output. There's only one signal that goes from the send to the effects and back (vs. two in a parallel loop).
It might just be dirty/corroded contacts in the send/return jacks. DeOxId works great to clean contacts and pots. Spray it on the tip of the plug and work it in and out of the send and return jacks. I suppose rubbing alcohol might be a convenient substitute, but don't take my word for it.