Vernon, thanks for that coupler chip info, and to GGG originally. I pulled the number and found the data sheet and ordered a few on ebay for stock, since it does appear to be a serviceable part. (Digikey have no stock) Its called a dual n-channel mosfet and can handle a continuous current drain of 3 amps. Wow!
After all that excitement I went downstairs and just for fun powered up the offending AA set. Guess what? It sounds just fine today; working perfectly. it ran for perhaps 40 minutes and never missed a beat; though I was expecting dead silence at any moment. Strange or what? But the jury is still out; it could croak for good any time.
Next I took a closeup pic of a 5V board stack, below.
In the upper left area you can see the pins where the two boards join electrically. Those pins look similar to the same kind of thing used extensively in TMCC days for plugging board together. I have not tried to pry them apart since this board set is running fine. But are these the pins that cause all the trouble separating the boards?
Anyway, thanks to all for the help! 
