(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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#1 2 years ago

I understand that Nvram is supposed to keep settings in its memory.
But how could it lose those settings?
Have a 6803 mpu made by fred swemmer. Never had a battery on it.
But three times I had it revert back to the factory settings. This over the course of about 2 weeks.
Nvram had been in there about 2 months. Same amount of time as the new mpu had been there.
Happened again last night so since I had an extra nvram I swapped the other into position.
Now I wait to see if it fails.
I guess all chips can fail. But could this be caused by anything else?
Odd thing was when I swapped the other nvram into place it did not have the same settings on it as when I had removed it prior. Should it have?
The extra nvram was removed prior when chasing an issue that turned out to not be related to the nvram. The switch on the left flipper button has an extra tab on it to be able to go backwards when in programming mode on a Truck Stop. The tab was not in place from when I had installed lighted flipper buttons.
So how does an Nvram lose memory?

#2 2 years ago

The 2nd NVRAM did the same thing tonight. Two days and six games later. Since they were both from the same source probably from the same lot number. Guess I can try buying one from another source? Any ideas what else it could be?

#3 2 years ago

Did you check the socket connections? Make sure all the traces ping out etc? Seems fishy that 2 would have the same issue. Did you get the correct chip for your board?

#4 2 years ago

The board is 2 months old from Fred swemmer. NVRAM is correct number.

I am new to this and read all I can here but have never seen HOW TO PING out traces. Problem just started a week or so ago. Haven’t emailed Fred yet. I will now.

#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.

#6 2 years ago
Quoted from EdHess:

The board is 2 months old from Fred swemmer. NVRAM is correct number.
I am new to this and read all I can here but have never seen HOW TO PING out traces. Problem just started a week or so ago. Haven’t emailed Fred yet. I will now.

PING OUT just means using a digital multi meter on the continuity setting and ensuring the traces from pin to pin have continuity.
Don't confuse new for good. Man made bound to fail.

#7 2 years ago
Quoted from barakandl:

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.

Honestly not sure if either of these nvram was this same setup or not. At work since I cant see it. Grapevine told me others had some issues with their nvram from fred. (chip is mounted on a board the has swemmer printed on it). The board has the sockets for either 6116 or 6264. Prior to your answer I went and ordered 6264 instead this time. This may help also if there is a bad trace on the board for the 24 pin socket by using the 28pin socket also on the board. Fortunately what I ordered was the same chip referenced in the link you posted for me, from Pinitech.com. Looks like i am on the right track... fingers crossed!

#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.

#9 2 years ago
Quoted from barakandl:

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.

Hey Wayne, I did not realize at first you were one I ordered the new Nvram from this morning. Thanks for jumping in here!

#10 2 years ago
Quoted from EdHess:

Hey Wayne, I did not realize at first you were one I ordered the new Nvram from this morning. Thanks for jumping in here!

Wayne (acebathound) is with Pinitech.

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