I have done at least two dozen NVRAM installs. I recently installed a Pinitech 6116 module in a Bally Game Show using the provided socket. I had no issues removing the old SRAM and did not lift any traces. Reinstalled the MPU and everything worked great. Settings were saved between power cycles. Been using the game for weeks without issue. Then the game started giving me "adjust failure" warnings from time to time on boot. If I just waited a about minute the game would eventually boot and work and play as expected, saving changes/scores just fine as well The frequency of these warnings and the need to wait for the adjust failure to clear increased gradually becoming needed more and more. In the last week, I now receive the warning every time the game is turned on and it never boots regardless of how long I Wait. I've been unable to get the game to boot since. Also, the word adjust is garbled while the word failure is clear.
I do not have any regular 6116 SRAMs (disposed of the old one) around but I do have another Pinitech 6116. Swapping in the other NVRAM does not change the behavior. I tested the voltage at pin 25 and got 5.08v which is within the NVRAMs range of 3.3v-5.5v. I also tested D1 which measures as expected with about a 100mv drop, I also shorted it with do change. I tested D2 and it seems fine. I tested continuity from the NVRAM module to connected pins on ROMs U26 and U27 and all pins except 18 and 21 had continuity as expected. Do pins 18 and 21 go somewhere and if so where should I test them? I also confirmed there are no shorted solder joints. I removed the board, reflowed the U25 RAM socket solder joints, and tested continuity again getting the same results as before. Reinstalled the MPU and still get Adjust errors every time without the game booting. I programmed new ROMs for the U26 and U27 but that didn't change anything. I programmed an Xflash test ROM by Ed Cheung (it's like Leon Borre's) and used the rest button to test the RAM, the test comes back bad.
I do not really see evidence of alkaline damage to the board anywhere. I did remove the battery holder which had some corrosion on the battery terminals. Part of the solder mask did chip off (looks like a manufacturing defect) on a trace between U44 and SRC7 which seems like it would be unrelated, I did jumper that with no change in the results.
Does anyone have any suggestions you might be willing to share? I am really at a loss. Should 18 and 21 have conductivity to somewhere I can test? I have a logic probe but am a total noob to using it. Really could use the help.