I'm still trying to find my MXR delay's hum problem.

[Chris Goodson]

I know it has to be something with the power supply.  When I hook up another one to it it works perfectly(I wasn't giving it enough volts before).  I've tried replacing the diodes and filter cap and it didn't fix it.  Is it possible for a bad transformer to cause this?

[smoguzbenjamin]

No, I think it's bad rectification... Have you tried adding another big cap across the signal wires?

[Chris Goodson]

Check the diodes again?  I tried an extra cap an all I got is what I think is refered to as motorboating.