Am trying to repair a Black Pyramid. The owner said it would reset, machine gun right slingshot and scoring would run up.

I have it at my place, adjusted leaf switch on sling and that seems to have sorted it out, however occaisionally scoring still runs up - it appears to be related to the pop bumpers and leaf switches either side of the pops, but i cant confirm that with testing i've done to date. In switch test, there are no stuck switches, and when i thump the playfield in switch test nothing actuates (however i think on these machines, switches in switch test need to be pressed for a second or so?).

The other issue is seemingly random resets, and adding of players. I would start a 1 player game, then part way through it would change to 4 player - i couldn't pick up when this happened - and the start button leaf switch is gapped properly, and doesn't get physically stuck. Also, on some games when it stayed in single player, it would completely reset, or sometimes get stuck on a score and light sequence - everything was frozen (scores and insert lights), until i hit start button again.

This happened with the original mpu, which looks a bit nasty with some corrosion, so i put a brand new NVRAM Weebly board in there, and it is still resetting and displaying all of the above behaviour. I tested the 5V on the MPU, and managed to get it on a reset when the ball drained as player 1 - the votlage appeared to stay a solid 5.2V the whole time.

I've reseated plugs on the solenoid driver board and power supply board, really have no idea where to go here. Could be a wiring issue?

Good idea - did this and still showed the same behaviour. Although with the coin harness unplugged, twice when i dropped the middle in line target, it added players to the game. Then i plugged the door back in, started a new game, adn dropped all targets and it played normally!

Then next game, i dropped the first target, and the game reset....

Inspected diodes on drops, all seemed to test ok in circuit. I unplugged the centre moving target in case that was mucking something up.

Now am consistently getting the game to end after 2 balls!!!! It counts down bonus after ball 2 drain, then goes back to attract mode!

Just about all caps have ben cut off switches from what i see

Wow, didn't realise you could set these to 2 ball! Thought either 3 or 5 ball with switch 16. Set to 3 ball now, and that at least works, however it still doesn't explain why i was getting resets randomly, or with a drop target hit - although this is not consistent. Have to go to work now, so will check other ideas later.

OK, did as instructed, and all tests report correctly ie: correct switch numbers every time - both with drops dropped, and left standing up.

I got the machine to fairly consistently add players, reset or add credits during gameplay when any one of the drops was down, but only when either pop bumper was actuated a few times, typically one or two pop bumper hits did not create the issue. Dropping the targets and firing all other switches would not result in credits added, players added or a reset.

A couple of pics

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Also worth noting the tilt actuated by the rolling ball doesn't work (no blade on switch), nor does the normal plumbob tilt. The tilt beside the plumbob does, as does the one under the playfield.

Also, i retried starting a game, unplugged coin door and when the in line drops are dropped, it still adds credits and players when you actuate the pop bumpers a number of times.

Really appreciate your help on this so far.

I've tried narrowing it down, and it is seemingly random.

I can't get it to exhibit the issue when drops are all up, however when any of them are down (one or all), i get any of the following, but not repeatable...

1. Either pop bumper adds credits or players (not together)
2. Either pop bumper and a couple of times the kickout hole at the top either slam tilted (game reset), or normal tilt (game freezes essentially until ball drains)

Its hard to identify if it adds the coin sound effect when it adds credits, since the soudn of the coil firing and other game sounds are all playing.

However... i decided to remove the under playfield fuse, so no coils fire - and when i did this, i could not get the problems to happen - it just scored as normal, no tilts or credits, extra players when i hit the pop bumper switches repeatedly. So this leads me to think there is a vibration issue when a coil fires - or some weird thing where coils are feeding a signal back to mpu or something? Not sure what i should be looking for though?

I jsut tested the vibration theory - and thumped the playfield in mulitple places (with the fuse in and out), and could not get a reset, tilt or add player/credit. I did get very occasional scoring (3k or 5k), but nothing else. Also noticed that sometimes the pop bumper firing would cause the hole at the top to kickout as well - again, not pattern or consistency.