(Topic ID: 245028)

NVRAM losing memory question?

By EdHess

2 years ago



Topic Stats

  • 10 posts
  • 5 Pinsiders participating
  • Latest reply 2 years ago by PinballManiac40
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#5 2 years ago

The FM16W08 chip used on typical NVRAM modules isnt quite identical to the normal SRAM chips but usually they work as a drop in replacement for most systems. If the replacement board is wired up the same way as the original Bally 6803 CPU it should work fine. Page five of the FM16W08 datasheet describes differences. https://www.cypress.com/file/41731/download

What NVRAM module do you have? On the NVRW ones there is a place to put a 10K pullup resistor on the /CE. It is needed for Midway arcade games to keep the NVRAM write protected at power up and power down or else sometimes the NVRAM gets scrambled or the board fails to boot. If the replacement MPU is wired up differently than the original you may want to try adding the 10K pull up to the NVRAM module if you can do a SMT resistor.

#8 2 years ago

Along with the 6264 NVRAM module I am going to also send you a 6116 NVRAM with the added 10k pullup on /CE. Try that one too and see if it fixes the issue.

If the game boot and plays the RAM chip and IC socket is probably OK. The system checks that it can access the RAM in the power on self test. Corruption of RAM is likely happening in the power down/up sequence.

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