Thanks for your help. The (tiny) reverb tank is mounted to the right side of the cabinet (facing from rear). I will check the wires tonight. I had been hoping to avoid disassembling the chassis, since I broke one of the nylon clips that holds the tube cover plate the first time I removed it to look at the tubes. That little Nylon piece has been there since 1985-7 and I broke it day 1. Anyway, I tried changing out tubes and the sound only got worse and still no reverb. I hope it is the wire, but I also have a well respected tech living near me who can give her a thorough service and I had planned to send the chassis to Mesa to have the Lead Drive/Master mod done.
Which brings up another question. Does anyone have that mod and do you think it is worth it? The gain difference between clean and Lead is so drastic that I'm thinking I need to just push the clean channel with my Bogner red pedal for the "mid-gain" and keep the amp in original condition.