Quoted from barakandl:
90% of battery damaged boards come to life and work 100% after replacing all IC sockets, replacing corroded parts, replacing headers, and cleaning up the copper tracks. When I would do there boards I wouldnt even attempt to diag beyond visual inspection before all that is done. It is kind of like redoing connectors. It sucks ass to do but if you want a reliability over long term and not possible continuous stream of new issues popping up it needs done.
Those AUGAT sockets are not the worst ones but they are still crap. Add battery damage and they are totally unreliable. Battery damage will fester and hide under those closed from IC sockets.
The order I would tackle MPUs....
Desolder / cut everything out. Sometimes if the battery damage is bad enough you cannot desolder things first.
Clean up the corrosion by stripping with an acid or sanding it off. Get any exposed copper shiny and nice so it will take new solder.
Coat any exposed copper with solder. Using the vacuum of the desoldering gun you can apply a nice thin layer of solder on top of copper to protect if from tarnishing.
Install the new parts and sockets.
Clean the flux off
test and diag the board (with less headache because the board is prepared).
I have seen people using clear wood finish over the copper and have tried that with wipe on poly. It seems to work fine, I did that to one a year and a half ago and still looks like I did it yesterday. I have done that to a few since then and all appear ok. I always wonder if there is a drawback when reworking something at a later date though? Also, what kind of acid would be best? After sanding I usually go over the area with Goof Off, that removes more hidden crud, then just Windex to clean away Goof Off so the poly won't have problems adhering.
OT: (just so I have the history fixed correctly) When you first put out the NVRAM Bally/Stern replacement MPU it needed game roms (didn't it)? But now the new version is dipswitch selectable like the Altek, only around $50 bucks less, is that correct?