(Topic ID: 254945)

Williams System 3 NVRAM does not save settings


By TheWiz

7 days ago



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  • 18 posts
  • 6 Pinsiders participating
  • Latest reply 4 days ago by TheWiz
  • Topic is favorited by 5 Pinsiders

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#1 7 days ago

I am working on a World Cup board set on the bench. I have got everything working except saving settings. I have replaced both male and female connectors for the 40 pin interconnect. Replaced all Scanbe sockets on the MPU and Driver board. Installed NVRAM. Installed MOSFT upgrade on the Driver board for the lamp matrix. No battery corrosion to speak of, fairly clean board. Ran through all Pincoder test ROMs and all okay. Ran through built in diagnostics and all okay. Only problem remaining is saving the settings. On reboot it comes up with 01 04. Turning off and on will get it to boot into attract mode. I can add credits and even play a simulated game. Turning off and back on and I get the 01 04 most of the time, every once in awhile it will come back up into attract mode with credits, etc. saved but mostly it comes back to 01 04.

Not sure what to check on the NVRAM to see what is wrong. Does anyone have experience with this problem?

Thanks for any insight anyone can give.

#2 7 days ago

Can you see the R/W line on the nvram toggling during memory tests?

#3 7 days ago

Do you have the interlock memory protect switch closed on the bench?

#4 7 days ago

zacaj Yes, R/W is toggling as well as all the other lines going to the NVRAM

xenon75 I don’t believe System 3 boards have memory protect, at least I can’t find it anywhere.

#5 7 days ago

Where did you get the NVRAM from?

#6 6 days ago

Check volts DC at p22 of the ram chip. If the blocking diode goes open the ram may still kind of work but be unreliable.

A problem in the reset section could not be write protection the ram at power up / down which can cause corruption. If you check the /ce pin of the nvram module it should be high while the cpu is in reset.

If you are easily able to, try the nvram in a different game to rule out a problem with the nvram module itself.

#7 6 days ago

Thanks barakandl I will check all those out. I know pin 22 voltage is good but I will monitor it as power is cycled on and off. May have to drag out the scope to see what is happening when. The NVRAM is from you, btw. I have several so i will try a different one to try to rule out the module itself.

#8 6 days ago

Did you have to install an IC socket for the NVRAM or was already on the board? just wondering if you had a solder short between adjacent pins or not.

#9 6 days ago

I installed a socket after removing the 5101. No shorts, all that has been checked out.

#10 6 days ago

Had 4.84 volts at pin 22, which is much lower than it should be from my bench supply. MPU/Driver is drawing a little over 1 amp, not sure if that is normal or not. Took the driver off and still had low voltage. Replaced the 100 ufd cap on the MPU and voltage came up to 4.94 so that should be okay but still boots up to 01 04 most of the time.

#11 6 days ago

I had a bad NVRAM on my end on a Disco Fever and after installing an 5101 and a battery, it all worked again.

#12 5 days ago

I swapped in another new NVRAM and still have the same problem but I am going to try the 5101 and battery and see what happens.

#13 5 days ago

If it goes into attract mode sometimes and passes the RAM test the NVRAM is probably working OK but corruption is happening, likely at power down or up, for some reason. When the RAM's check digit corrupts you get audit mode on the next boot up.

The power on reset circuit write protects the RAM when the voltage is coming up and down. A failure at Q6 or D19 could mess up the 5101 CE2 yet the rest of the power on reset circuit allowing writes to happen when the CPU is out of program.

Quoted from Brewchap:

I had a bad NVRAM on my end on a Disco Fever and after installing an 5101 and a battery, it all worked again.

Try that NVRAM in another game if you easily can. If it works in another system it might be worth checking the system 4 mpu's Q4 and D18. The NVRAM is powered from this circuit which bangs off of the reset. If Q4 or D18 is bad the RAM chip would only be powered when batteries are installed.
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#14 5 days ago

Thanks for the explanations. I am 99.99% sure the NVRAM is good. Problem must be in the reset side of things as a couple of you have suggested. I have checked a couple of the components in this section but not all of them. I will work on it this afternoon when I get home since it is such a rainy, dreary day in Ohio.

#15 5 days ago

Transistors and diodes in the reset section all checked good in circuit but I replaced them anyway, still same problem. All components checked good on my tester after removal, btw. Took NVRAM out and put in a good 5101 and batteries, still same problem. Replaced the 3.3 ufd cap in the reset section with a 4.7 ufd cap, still same problem. The 3.3 ufd cap measured 3.7 ufd out of circuit with a 3.9 ohm ESR.

Using a logic probe CE1 on power up, starts high then after about 1/2 second it goes low then toggles. CE2 starts low then goes high and toggles. Those look to be doing what they are supposed to do. Can’t really tell what happens on power off since logic probe loses power. So what protects the cmos contents when power is removed?

#16 4 days ago

Changed the .01 ufd cap below U19 (cmos ram) to a .1 ufd cap, still same problem. Changed the 22 ufd cap in the clock circuit to 33 ufd, same problem, maybe a little worse, idk. Anyway, that is all the changes I can find to do that has been suggested.

#17 4 days ago
Quoted from TheWiz:

Transistors and diodes in the reset section all checked good in circuit but I replaced them anyway, still same problem. All components checked good on my tester after removal, btw. Took NVRAM out and put in a good 5101 and batteries, still same problem. Replaced the 3.3 ufd cap in the reset section with a 4.7 ufd cap, still same problem. The 3.3 ufd cap measured 3.7 ufd out of circuit with a 3.9 ohm ESR.
Using a logic probe CE1 on power up, starts high then after about 1/2 second it goes low then toggles. CE2 starts low then goes high and toggles. Those look to be doing what they are supposed to do. Can’t really tell what happens on power off since logic probe loses power. So what protects the cmos contents when power is removed?

Sounds like CE1 and CE2 are working as they should. Not sure what is going on.

At power down as the voltage falls below the breakdown point of the zener diode, Q6 should turn on grounding CE2 which should write protect the RAM. Maybe check the voltage no each side of the zener diode?

I have never tried it in a WMS game but you likely are able to defeat the overly complex reset section and the NVRAM should still work fine as it does in a Bally MPU. If you lift Q6's collector off of the board and put the NVRAM right on the +5vdc power supply by removing Q4 and jumper on the PCB from Q4's emitter to collector you may avoid some an odd timing issue if that is making the RAM corrupt. You can try that if you are feeling dangerous. Shouldn't be hard to reverse if it does not work.

#18 4 days ago

Zener looks to be working okay. 6.8 volts across it, 5.69 from ground to anode. I may try the reset mod above just to see what it does.

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