Reverb problem w/65 reverb head

Hi all,
I just discovered this site and it's awesome! I have two MM amps and I love them both, but I'm having to part with one. I just posted it on e-bay. The reverb has never worked since I've owned this amp (bought it used).
If you bang on the head, you can hear the springs rattle as long as the reverb knob is turned up enough. The footswitch will turn this sound on and off, but while playing through the amp, no effect can be heard.
This amp does NOT have a 12ax7 tube, if that matters.
Any ideas what could be wrong or where one could turn to get it fixed? I've put it up for auction, but I'd at least like to point the winner in the right direction to get it repaired if I could.
I bought both of my MM amps second-hand in the Chicagoland area. They both have a lot of corrosion on the metal parts (but not much on the transformers, thankfully). Are MM amps more suseptable to corrosion/rust than other amps or is that normal for amplifier of this vintage?
Thanks in advance!
Ryan D.

Sounds like the reverb output side is OK, but
the input side isn't.
Try clean/tighten the I/O chassis/tank RCA jacks.
If that's not it, here are some other Fault possibilities, (from easy to hard):
.Cable from chassis to tank;
.Tank input jack to local transducer wires;
.Tank input transducer;
.Chassis reverb send circuitry.

Langley,
Thanks for the response...
Some of this is a bit over my head, but I've already checked the cable and it's known good (reversed it and swapped it for a known good one).
The other suggestions are new territory for me. I'm not affraid to take the chassis out of the cabinet, but I'm a bit intimidated to start poking around itside. I don't have much experience with electronics beyond things that are modular.
Having admitted that, I do think you're suggestions seem logical. I do have a friend who is an experience amp tech. I never thought to ask him to look at this for me, but now I've made the mental connection, I'll ask him to check the things you suggest and let you know what I find out.
I really appreciate the info.
Thanks,
Ryan D.

If you have a pal that has a Fender amp with reverb, borrow the tank out of it and try it. The tanks on MM's do seem a little fragile for some reason. I've put two in my work amp in 4 yrs. Just something that happens sometimes. Mike.

Thanks for the suggestion, Michael. I have a Fender and another Musicman. I'll give it try if I can. My ebay auction ended and I'll be shipping it off to it's new owner -- but if I get a chance to try this before I have to ship it, I will.
Ryan D.