Okay, it sounds like we are fixed up! Received the new B-Band 29R UST (about $43 via Amazon.com).
Removed the battery, strings, disconnected the old transducer, removed it and the saddle and cleaned up the saddle area. There was a small shim under the saddle, kept that.
Opened up the A15 preamp to check all other connectors. I had to enlarge the pass-through hole in the preamp casing for the new 29R plug, otherwise the connector is the same - 2 pins.
The transducer just fit through the bridge hole and sat snug into the saddle groove. Careful not to pinch the UST or let it slip out of place, I replaced the saddle and one string to hold the transducer in place while I plugged the pickup into the preamp and reassembled the preamp. (note: if you plug the pickup connections backwards it will hum). Re-inserted battery and plugged the guitar into an amp to test the UST by scratching the saddle. Good-no hum!
Used double-sided foam tape to mount the preamp inside. Replaced all strings, tuned up and viola! - no hum, no crackling, eq and vol controls work - it sounds good.
Other than the time and effort, I'm glad this was basically a $50 fix. The guitar plays great but I'm not that enthused about the B-Band pickup system - it's clear and operable but the tone controls are not very effective. Still, it's a beauty and it'll get some stage time for sure.
Hope this helps the community in some way.