I've been working on this Stern Lightning MPU for a while now. I have 3 boards for it, one crappier than the other. I did however have it working fine at one point, I was just working on some switch issues when the MPU died on me, and the LED just stays on solid. I had already replaced the game ROM's U1-U6, which seemed to help it get going initially. The sound cables were another issue but I made new cables which did the trick there.

So after it died I went to the flipperwinkel site and went through all the procedures, I even made a test fixture so I could work with it easier on the bench. I replaced sockets for U9, U11, tested the reset circuit and it seemed to be fine, bought new 6800, 6820's for U9-U10,U11, voltages seem ok, and all sockets seem to have continuity down the line. I spent all day going through every website and procedure I could find, but nothing really makes sense, I still have a solid on LED when I start it up. There is no battery damage, so the only thing I can think is that my U9 6800 or U11 6820 was bad and the new ones I got are bad as well? I bought 2 of each just in case, and neither has solved my issue.

I did the short R1 and R3 to ground test and the MPU dropped to .4v or whatever it was supposed to do, shorted pins 39 and 40 on the MPU and it didn't reset, etc, I think I covered everything I can with a DMM and no logic probe but still no joy. I hope I've explained myself well enough, and I hope someone can shed some light on this problem, I know it can be hard to find. Thanks.

Thanks Bob, it was only after I got tired of installing-reinstalling the board every time I tried something that I made the test fixture, just much less work than hooking it all up again. I'll give it a shot though just for kicks.

FWIW I have fully replaced the J4 connector and pins as well before trying it on a test fixture.

I know that is probably the best solution, I just hate giving up, especially knowing that it was working fine. I'll keep trying before caving in and buying a new board. Anyone have any suggestions?

Thanks for the advice Spybryon, I did all that and shorted 39/40 and LED did not turn off. I must be interpreting the info on that page wrong, I thought if the light didn't turn off the reset was ok. I've ordered all new parts for reset circuit from GPE. I'll post my results, wish me luck lol.

Good luck with your MCP100, will it replace the entire reset circuit or something?

I used my dmm lead to jump 39,40 so I'm pretty sure it made contact. I have buzzed out the chips for continuity and they're good. I don't think its traces since it was working fine in the game before it quit but I could be wrong. If the new parts for reset don't fix it I'll probably have to go the route of a new mpu I guess. I will spend some more time checking traces in the meantime but so far they've all tested good. Thanks again, I'll update after repairs.

Just finished rebuilding the reset circuit with all the recommended diodes, resistors, capacitors etc... still no joy, just a solid light. I kind of expected that, this is a weird problem. Still I'm not ready to give up just yet, and I'm always thankful for any advise anyone can throw at me.

Yes, I tried it in the game after using the test fixture, same results. It's strange to me that it was working and powered up when it quit on me, so it would seem like a component is fried? I had two of the MPU 200 boards working at one time, now they're both doing the same thing... I've just gone over all the pins on the chips to check for connectivity and they're good it seems.

I've handed it over to a friend of a friend who's an electronics technician, we'll see if he can get some results. I'll post whatever I find out from him.