Hey everybody. Not sure if you remember a couple of previous posts about my recent 1980 Black Knight project. For starters, it was in a barn for the last 20 years and completely covered in filth. No problem. It actually cleaned up really nicely. It's a decent player machine IF I ever get it working. Rebuilt all 4 flippers. Did some basic stuff that I know how to do.

The game has the typical GI and backbox lighting but never boots. The very first time I plugged it in, I heard a loud humming (assuming speaker) and then it stopped. I noticed after I lifted up the playfield that there were several metal pieces stuck to the speaker magnet in the bottom of the cabinet. I can't imagine that was good for it when I plugged it in with all that metal stuck to the speaker magnet. Not sure what damage that could do. This is my first question...

Regardless.. No display, no sound, no audit/test, solenoids trying to fire or anything. My current MPU LED is stuck on 1 (pictures to follow). I purchased a refurb MPU and Driver Board from someone. Once I installed those, I had playfield lights for a few minutes and then never again. That replacement MPU/driver had new everything including 40pin connection. I tested the voltage to the MPU and it tested 4.96v in the test post by the battery holder and 13.86v in the top left test post.

The seller of the refurb MPU and Driver was kind enough to let me return the boards. He told me the driver was fine but that one of the MPU ROMs was "completely fried" and the other three had "scrambled data". So I bought a new Rottendog replacement power supply. Not sure if I needed it but bought it anyway. This is now installed and everything remains the same.

The question is... is it possible that my original power supply fried both my original MPU and the refurb MPU? Could it be problems with the wiring/harnesses? If my original power supply had problems, is it possible that this new Rottendog power supply may not cause the same MPU damage (assuming my old power supply was the culprit).

I'm kind of losing my mind here. Not sure where to go next. What to test, etc. I have a basic DMM to test but not even sure what to test. I don't want to destroy yet another MPU when I get one.

Thank you for any help. I will post pictures below and please let me know if you want any other photos.

Below are photos of the original MPU locked with error code 1 and the new Rottendog Power Supply connections in case anything jumps out as an obvious problem.

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Thanks for the replies. Yes, I have confirmed that the cables in the cabinet/neck all match up. That doesn't seem to be the problem, @gnatty.

zacaj
You could be right about the loud hum coming from the sound board but it was VERY loud like something bad was happening and then it just stopped and I've never heard another peep out of it.

zacaj Nothing happens at all when I play with the volume or test button. I haven't checked to see if the sound board is getting power. I will try that tonight. At this point, the sound/display is the least of my problems. I just want to figure out why my MPUs keep locking up or being damaged.

zacaj Thanks for the check list. I will go through these steps tonight. I just printed out the schematics. I think I should be able to test those voltages even with my low skill level.

Stupid question but how do I actually check voltage from the PS to the MPU at the 1J2 connector? The holes are so thin in the female connector that I can't figure out how to get the leads on my DMM in there. Thanks

Hi again, folks. For anyone that may still be playing along, I had my original boards repaired this weekend. Previously, the MPU was locked up with error code 1 (indicates possibly IC13 fault). Turns out IC13 was definitely faulty along with several other smaller problems. The Driver Board was in pretty good shape and I've had the lamp resistors replaced. Power Supply needed several caps replaced. The sound driver board had a bad rectifier. Display board was OK.

All this to say... I have a working Black Knight now. I'm very excited because I thought this would take a lot longer (and more money) to get going. It plays OK. Lots of smaller issues were discovered now that I can actually boot a game and see how all of the playfield electronics function. The largest issue at this point is that pretty much ALL of the drop targets need cleaning. They are not dropping correctly when the ball hits them.

I'm wondering if anyone has any advice on where to start? I assume I need to desolder the coil, remove the switches and take out the entire component to clean it. The targets are functioning in that, once they drop, they do pop back up when they are supposed to. They are just either very hard to drop or sluggish.

One other strange occurrence is that every once in awhile the ball trough kicks out 2 balls instead of 1. I doubt that is part of the actual gameplay.

Also, Travish I totally understand why I needed that metal plate on the 2nd level now. I'm surprised the plastics weren't destroyed already from that kicker popping balls smashing into that top plastic. Thanks again for that!

Thanks for the info guys! I'll try this out this week. Travish - I'll get some more pics uploaded. It cleaned up better than I expected. I almost think the filth on it may have protected it for the 20+ years it sat in a barn. At least it stayed dry.

The only thing that will drive me nuts is the Backglass is in terrible shape. Some genius taped every inch of the inside to prevent it from further flaking but that tape is so old it's yellow now. I just can't bring myself to spend $300+ on a new one at this time so I'll just have to live with it for awhile.

Travish Please excuse the mess in my garage! My pinball machines aren't allowed in the house unless they are working!

I plan on waxing it a couple more times, swapping out with LEDs and fixing the mechanical issues and then hopefully being done with it for awhile.

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