I've got a Xenon that I'm trying to get to boot. When I turn the game on, a few play field lights come on, there is speaker buzz, and the LED on the MPU goes solid dim.

I took the MPU out and fed it +5VDC, +12VDC and GND through a computer power supply and (after replacing the 5101) got the 6 flashes I'm looking for.

Per "the guide," I put the board back in the game, I disconnected all the connectors except J4, the power connector.

At this point I measured the +5VDC and + 12VDC test points and got an odd reading of +4.1VDC and +11.1VDC respectively.

Also per "the guide" as long as your power supply is good, with everything else disconnected, a known good MPU should boot.

Admittingly, I got a little lazy (the power supply boards are very servicable) and I found a good discount on a new Rottendog power supply.

Threw the new power supply in, same result. +4.1VDC on the +5VDC test point and +11.1VDC on the +12VDC test point.

Here is what I don't understand. Per "the guide," you only need the power supply hooked up and J4 on the MPU plugged in to test this board in the game. However, there is no +5VDC coming from the power supply, apparently +12VDC goes to "J3 pin 10 +5 regulator input" and J4 on the MPU is the power connector but it's expecting +5VDC.

Also, with all MPU connectors plugged in, same symptom, a few lights, speaker buzz and a solid dim MPU LED.

Just for good measure, I already have this coming:

https://www.greatplainselectronics.com/proddetail.asp?prod=BALLY-P22E-KIT

Any ideas? What's the simplest way to get +5VDC and +12VDC to the MPU so I can start working from there? Is just having J4 plugged in the MPU sufficient? Is my problem really on the solenoid driver board?

Thank you so much for your reply. The caps are in the mail anyway, and if that doesn't work I'll switch out the LM323k.

It sounds like the guide has some bad info in it. Here is what is says:

"The J4 MPU Board Connector.
If you don't want to make a work bench test fixture for repairing your Bally MPU board, there is an easy way around this. Assuming your Bally power supply is working correctly in your game, when testing a Bally MPU board, you only need to use connector J4 on the MPU board. The J4 connector is the power connector. With it only attached and a working power supply, you can quickly test your Bally MPU right in the game."

So, is this a bogus test? It sounds like the game needs the (solenoid) driver board to convert that 12v to 5v so I don't see how just having the power supply and the MPU plugged in could possibly get it to boot.

If that's wrong, it cost me about $70 but maybe I'm not understanding it correctly.

Got it. It's on me, but even if it wasn't the guide has helped me hundreds of times so I couldn't really bitch about it

Changed out the three caps from the GPE kit above and the game boots right up. Thanks.