Robotron High Score Save Issues

Waterborn

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I have a high-score battery back-up on my Robotron cab. Recently, once about every three or four times I power down the cab, when I turn it back on I get a "factory defaults reset" message and my high scores are no longer there (and of course any setting changes, such as free play, have also been reset). I checked to make sure the auto-reset toggle was not "on". I also put new batteries in the back unit, but it still resets every 4th or 5th time I power down the cab. Any ideas on how to fix this? I lost my 1.7 million point high score :?(
 
Are you using an original power supply or have you swapped it out for a switcher?

ken

That's the first question I would've asked...

Sounds like you just might be losing voltage to the CMOS when it's powered down. This happens even with new batteries if the battery holder itself has started to corrode or weaken the spring tension on the battery holder.

Try replacing the battery holder (you can buy replacement battery holders; some pinball parts websites have them for sale, or try Arcadeshop) or get a more modern high score battery kit.

If you already have a more modern high-score battery kit installed, forget everything I just said :)
 
Double checked the ps and it appears to be a computer type 350 W model (not an arcade switching ps). The battery backup unit looks to be in good condition. No evidence of corosion or other issues. I may check into a new battery back up first and then look at replacing the ps if issues persist. I am not experiencing any other issues with the cab, so I would figure that the ps is ok. Is this a safe assumption?
 
That is a switching power supply. What happens is that with the original Williams power supply, the large capacitor on it will continue to supply power to the CPU for several hundred milliseconds. In the meantime, the unregulated power will drop to zero, which invokes the CMOS memory protection circuit. The power supplies do this because the old Motorola CPUs (6800 & 6809) had a tendency to write randomly through out the memory space when the voltage dropped below a certain threshold. This includes the CMOS memory space.

Switching power supplies (including yours) do not have that reservoir of power to keep the CPU alive until the CMOS protection kicks in (both +5V and +12V go down at the same time) so as it is being shut off the CPU can randomly write garbage to the CMOS.

It usually doesn't overwrite the settings unless the memory protect switch on the coin door has been defeated or is missing. There is a seperate protection circuit for the factory settings part of the CMOS address space, but I have heard that some boards have a hardware bug that cause the factory settings protection not to work.

The easiest way to fix this is to go back to an original power supply. If you have the original board and it is not working, I rebuild PS boards for $20 + shipping. If you need a rebuilt PS board, I sell them for $30 + shipping.

The other way to fix it would be to build a board that sits on the PS cable and provides enough capacity to keep the CPU running until the memory protection kicks in.

Or just live with high scores and setting being reset.

ken
 
The other way to fix it would be to build a board that sits on the PS cable and provides enough capacity to keep the CPU running until the memory protection kicks in.

Sorry to half hijack, but how long do those caps have to last? Just a few milliseconds? My Robotron boards loose settings and scores pretty regularly it seems, at least once a week. And that has to be on the 12V AND 5V lines?
 
The +5V only has to last a few milliseconds. Just long enough for the +12V unregulated to drop off. This is what triggers the CMOS memory protection circuit. Basically this circuit turns off the write enable to the CMOS chip, so that if the CPU decides to write across the CMOS memory space, the CMOS memory chip ignores it.

The 12V lines should not have any additional capacitors on them. You want them to discharge as rapidly as possible.

The trick is to make sure the additional capacitors added to the +5V line do not draw too much surge on powerup or you run the risk of blowing fuses. Or the simpler appraoch would be to just use an original power supply. Once I figured out what was causing the problems, I pulled all of the switchers out of my Williams games and haven't had any problems with CMOS overwrites. As far as I know this only applies to Williams games.

ken
 
Double checked the ps and it appears to be a computer type 350 W model (not an arcade switching ps). The battery backup unit looks to be in good condition. No evidence of corosion or other issues. I may check into a new battery back up first and then look at replacing the ps if issues persist. I am not experiencing any other issues with the cab, so I would figure that the ps is ok. Is this a safe assumption?

You are not understanding what is being said. The PS is your problem. Swapping in another switching PS will NOT fix the problem. If you want to FIX the problem, you will need to install an original linear ps.
 
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