Williams Stargate

jimk

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I'm trying to determine if I've resolved a resetting issue with my Stargate. The power supply has been rebuilt and appears to be within specs. Before the latest round of repairs, the game would randomly reboot during play. After, I've haven't witnessed it rebooting, but I've noticed the score from the last game will not carry over through the attraction cycle indefinitely. At some point in between my checks, it clears back to 00. Is this normal behavior or should the score of the last game stay until powered off?
 
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are you getting the factory settings restored message?

did the batteries on the MPU leak at any point? the alkaline spreads into the power circuit for the CMOS first -- it will eat many more things up if left unattended for about 20 years.

it should retain scores however. I recall this being a thing though, where like either the scores crap out, but the CMOS settings stay. it's weird. I'm fried right now and can't process this anymore.
 
There is no acid damage, but I've removed the batteries in favor of nVram. Also, there is no evidence of any errors or resetting to factory other than the last game score setting back to 00. The actual high scores are being retained it's just the score of the last game played isn't held until a power down or a new game is played.
 
If the game crashes / reboots the CMOS ram contents could likely be scrambled, even with NVRAM. The CPU stops executing code properly and may dump on the RAM chip.
 
I think I'll try putting it test and running it for 48 hours or so to see if it resets out of test.
 
it is possible for the CMOS to get corrupted and the game can't detect that the data is bad and force a factory reset.

everyone swears by NVRAMs but I still use AAs with pinball remote holders.

I don't know if your NVRAM is socketed and can just unplug. I would try removing it first.
 
I use nvram in all my Williams games, Robotron, Joust, Defender, and soon a Stargate I'm restoring. They work great but i find it's important to have your 5v set right especially if you have a switching power supply. If your 5v is too high then it's possible it's write protect won't trigger in time to prevent corruption of the CMOS data during shutdown. If it's too low then you could have weirdness even during gameplay.

From what I recall, on Defender if a high score got corrupted you would still see it in the high score table but with weird characters, like a ? symbol as part of the score for example. I noticed they fixed that with later games like Robotron (and presumably Stargate) where the game will do a verify on the high scores and remove corrupt entries. So if you suddenly see a high score entry dissapear it's because it got corrupted somehow and the game caught it and removed it.

I mention voltage because I find Williams games are weird because it seems like they can work fine even as low as 4.6v but that may cause weirdness with the nvram. If you measure your 5v at one of the RAM chips, what reading do you get? It's just a guess but maybe your 5v is off a little. This type of error won't get caught in any of the tests because the machine works fine at low voltage , but it makes the nvram get finicky.
 
the 6809 CPU writes garbage data when you turn it off. the unregulated +12 circuit holds it long enough for the CMOS protection circuit to activate. I don't know how that +12 and the CPU go together, seeing as how the CPU doesn't use 12 volts, but whatever. +12 goes out first on a switcher, that's why it's usually a problem with those.

I'm curious to know how the NVRAM ties into +5 though. it plugs into the same spot as the old CMOS, but that gets its power off the battery circuit.

you'll see in a number of Food Fight NVRAM related threads that the +5 is very important to the integrity of the NVRAM. the problem with the Williams hardware is that there's a number of factors that result in losing power. I would think at a certain point if you run your switcher very high instead of correcting what's causing the drops in the first place that it could eventually burn the plug up. you have a single +5 wire going to the board and pretty anemic ground.
 
Check out how the CMOS ram is wired up in Robotron.

http://www.robotron-2084.co.uk/manuals/robotron/robotron_upright_drawing_set_mar_82.pdf



The NVRAM is not directly on the 5v rail. It is powered by reset delay circuit. Reset delay uses 12v. The IC1 7410 decoder is powered the same way. This is why the 12v circuit is critical to NVRAM contents and why switch mode supplies act differently than linear supplies.

The FM16W08 based NVRAM device used would probably work just fine directly on the 5v rail, but would require pcb modifications.

There is a pinball system (Bally -35) that uses a similar idea for the power on reset delay circuit to power the battery backed RAM. In that system the FM16W08 based NVRAMs work fine directly on the 5v rail.
 

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yeah I remembered it has its own Dallas battery built in. LOL I work late, so you get me in rare form at about 6 am when my brain is mush from all the stuff I worked on all day.
 
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