Fender Ultimate Chorus reverb diagnostic help please :)

DartmoorHedgehog

The reverb has stopped working on my bandmate's amp.  It's a Fender Ultimate Chorus 2x12 SS combo.  Turning the reverb knob up all the way does nothing, but the dry sound still comes through.  Wiggling the RCA connectors on the tank apparently makes a crackle, so presumably the return part of reverb circuit must be working.

Any suggestions for what he should check next?  I thought if the tank was dead there would be no sound when the reverb was turned right up (isn't it just a mixer from 100% dry to 100% wet?) but that may be utterly wrong.

DartmoorHedgehog

It's fixed - turned out to be a broken wire inside the tank.