(Topic ID: 196740)

Stern mpu 200


By gregh

2 years ago



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  • 6 posts
  • 4 Pinsiders participating
  • Latest reply 2 years ago by gregh
  • Topic is favorited by 1 Pinsider

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#1 2 years ago

I'm trying to get a stern mpu 200 going in a big game for my buday. I'm a little confused about the rom configuration that came with the game though. It looks like u1 u2 and u5 are 8k chips with u6 being a 2716 eprom. Would this be factory, or has someone at some point swapped a 2716 in place of an 8k? The reason I ask is the mpu will flash 7 times but then lock up. No displays or anything. The scematic doesn't show this combo that I can see, and the jumpers are totally different for the 2716 according to the manual. I hope this makes sense. Before I start changing stuff around I wanted to see if anyone knows if this is correct.

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#2 2 years ago

Have you checked against http://www.twobits.com/stern_jumpers.html? I don't have my big game anymore but I definitely had the same 2716 in u6...

Maybe your 5101s are too slow, are they original? Is this in the game or on the bench?

#3 2 years ago

Immediate crash after 7-flashes is, in my experience, possibly due to bad NMI (Non-Maskable Interrupt) from the 555 timer IC (little 8-pin DIP). The NMI is supposed to tell the MPU to scan the switch-matrix, and strobe the displays, lights, etc., but if it's coming too fast it will crash the 6800. Could be the 555 itself, or associated capacitors/resistors. Alas, short of shotgunning parts (replace and see if it helps), you'd need a scope to diagnose this failure.

#4 2 years ago

Unless you're really anal about getting it back to 100% 'as factory', as long as the jumpers match the chip, you should be good.
Look on the schematic straight above the part you took a picture of your monitor of, and you'll see the different chip pinouts. (i.e. For a 2716, pin 21 is +5, and pin 18 is /CS) All the jumpers are in the schematic above each of the chips with dotted lines and all the E-points.

I doubt, though, as others have said, that that is your issue.

#5 2 years ago

Yah I checked the mpu against the two bits list and the jumpers are correct for this configuration. I don't have a scope so it's either an alltek or shotgunning parts.

Thanks for the help guys. Gotta make a decision on what to do now.

Cheers

#6 2 years ago

Oh I'm testing in game. The other step I was possibly going to try is getting one of the dual 5101 nvram chips. Think it would be worth a shot? I've read that can be another cause of crash as stated above.

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