Quoted from pinlink:
ok guys, I think I may be on to something here (at least I hope so).
If you look at where the U25 socket is installed there are 7 solder points underneath where the RAM sits. It appears that one of these solder points (indicated by the red arrow in pic below), may have a broken trace.
I have tested continuity on all 7 of these solder points to legs of the U26 Ram, and the only one I can not find continuity for is the one pictured above.
Can someone please tell me if there should be continuity between these two points in the picture? If so, Could I just add a jumper to these points (indicated in blue)?
That board looks like the trace was damaged by a screwdriver prying a chip out of the socket. I've seen that happen on many boards where the screwriver has sharp edges and ends up resting on the board when prying up instead of the plastic socket housing.
If a trace is severed that would explain why neither the NVRAM or old SRAM work. I don't have a similar board out to look at the traces but you should be able to pull down the schematics from IPDB for your game and reference those. From the pictures it sure appears that one trace is severed.
A while back I bought a spare MPU for one of my other games. I bought it as non working and found bad traces from a prior repair. Attached are some photos of how I fix traces like that. I'll remove the sockets, clean that area, and make new traces on the top of the board. When done it is like it never happened.
Putting a jumper on the back will also get the job done.
I hate batteries on MPU boards. Seen WAY too many boards messed up by battery damage. The only exception I make is for the coin cells which don't seem to leak like that. I put NVRAM in my own games and most are already done. Going to do a Volcano and my Pinbot next. NVRAM works really well and that usually isn't the issue. If there are problems it is with the work getting to that point. In some cases a bad DIP socket, and in others messed up traces and pads. Things happen but they can all be fixed.
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