Ok, so this one has me stumped. Unfortunately, I've done some thread searches and similar issues haven't seemed to be overcome easily if at all by anyone. I'm determined to get to the bottom of it, but it's wearing me thin, so I'm reaching out for help.

This is not my game, but one I am working on for someone else. When I first looked at it the 128x16 display wasn't coming on, but did after awhile, so I figured it'd be usual voltage issues. Anyway, when I got it into my garage, the voltages are all perfect on the display. When it boots up the display ROM version shows, then it'd go to "Open the Door". Once the door was opened, the game would boot up but the display would be blank.

I put new batteries in and tested that they were good down to the RAM, even put a new CMOS RAM chip in. Now, the display boots the version and shuts off and then goes into attract mode. Everything else on the game works, you can play a game even and the display will come on occasionally but not be computing properly and one time showed "Command Overrun".

I've tried about everything I can think of. All voltages to display are good, display ROM has been replaced twice, game ROMs replaced, 6802 CPU 40 pin replaced, 6264 RAM replaced, new batteries all tested down to the RAM chip, swapped ribbon cable with known working, taken CPU board out and looked for any sign of corrosion - board looks great. Noticed on broken pin on CN21 on CPU, replaced, but that was to sound board and didn't do anything with this.

One thing I did notice that I've included a picture of is it looks like the caps at C131-138 before CN1 connector were burnt. However, there is no connector at CN1, so would this even be an issue? Could the 6821 segment/sound control PIA be a potential?

Any help greatly appreciated! The display is totally fine, not outgassed or anything, it's just like it's not getting proper data to operate correctly and I can't figure out where that issue lies.

IMG_3381.JPG

bumping, anyone?

Evening bump

Bumping, have Leon's test rom on the way in to test PIAs. Happy for any other guidance - thanks!

So, I used the test Eprom and on the display PIA I got a low signal only from pin 2. I replaced and double checked, and was getting proper high/low response on my logic probe.
Plugged everything back in thinking surely this was it, still no dice. Any suggestions? Thanks!

Took videos today, figured I'd post:

Video 1 - Boot up. As you can see the display brings up its ROM version and then blank. Game will go into attract mode, you can even play a game (kind of). There's a lot of switch adjustments and issues that need to be addressed, but I need to get this display issue fixed before I mess with that.

Video 2 - This shows that CPU completes normal boot sequence. There is a block resister on the power supply board that looks a bit hackish with a cap tied across it that I show at the end. However, with voltages in good measure, I didn't bother messing with this. Should I consider it a possible culprit?