This is my first System 3 project. When I turn the game on I get a bunch of garbage on the display. The game goes no further. My boards are all blinking except A8, the display controller. (The MPU board is blinking quickly and not on a constant tempo. Is that normal?) A8 is just a solid light.

I've read the repair guides and I have tested all the HV portion (and replaced parts)of A8 and I've also installed a new U8GAL chip. Still no change.

I have no clue where to begin. I'd order a new display control board but I don't want to just throw money at something unless I know thats the problem. Thanks for any advice.

MpB85cHaQBe9WQInpYD1Ng (resized).jpg

Another update: When I unplug all the ribbons from the display controller board and the ribbon cable off of the cpu, the cpu still has the same "flickering" instead of a constant flash.

A bit more info. I read a post that discussed checking the watch dog circuit by probing pin 40 of U1. While in that process when I touched pin 40 or maybe shorted pin 40 and 39 the game beeped and went into attract mode. The CPU now has a steady flash rather than a flicker. The light on the display control board is still solid.

Thoughts? Does this indicate the watch dog circuit is bad or U1 is bad? I assume I'm having problems with both my CPU and my control board with this happening?

Good info. Thanks. Dumb question(s), is this power supply fixable? Where does it originate? I’m assuming this will still have no impact on the display control board?

It is. I measured the voltage and I’m getting a steady 5.1v. I also adjusted it sound to see if it would make a difference. I got no change

trying to get a new rom. I've also ordered new capacitors for C20 and C21. Not sure how to proceed with the display control board. Since they need each other to boot the game I'm not sure what to do. How will I know if my mpu is working correctly if my display controller isn't and vice versa?

Board was sent to Chris Hibler for repair.......like new now!