Got it today, took it apart. Battery leak juice got in there pretty good, there's green moss in many places. Oh well.
OOoohhkay, here's some pics. The 4 AA cells are in a plastic holder. Once the holder removed, the dried remains of battery juice under the holder are evident, clearly it also osmosed through the PCB vias to end up on some circuitry, where over the years it patiently chewed away at stuff.
Great.
Also, one single pin on a SRAM all the way on the other end of the PCB has green fuzzies on it. Weird. I'm thinking it needs replacing because how can I be sure there isn't more green moss waiting to chew its way into the package?
I guess vinegar and the old 0000 steel wool will clean up the PCB nicely exposing which traces will need jumpering. I suppose the bunch of chips will need to be replaced. I've never seen packages like this except in old stuff, sort of very rectangular SOIC packages. Interesting.