Friend was playing my game. All of a sudden color DMD drops off and game starts randomly shooting balls from the launcher. Balls are then stuck in the subway and it will not put them back in the trough. 2 coils are randomly firing and I cannot use flippers or anything but can start a game.

I have a shady high power board so i'm sure that's the culprit, its had some "work" done to it prior to my ownership. Test point 1 reads 0... since it is unregulated 12V it should read .... 12V right? Yes I just want to be sure if this is the main culprit.

18V is jumping up and down from 15v-19v (assuming that's normal since it's unregulated).

I have put in the old screen, that screen will turn on, game remains the same.

I've troubleshooted with the WPC guide before but one thing is confusing to me when testing BR's and Caps

It tells me to turn on the game testing BR2, okay easy enough. However then it just says this below... Am supposed to stay connected to a bridge rectifier to test a cap? Am I confused?

For the capacitor, turn your meter to AC volts. Note that inexpensive meters may give false readings here. Ideally, your meter should be a true RMS meter. Good capacitors will read about 300mV AC. Bad capacitors will read up to 2VAC. Anything over 1VAC indicates a failed/failing filter capacitor at C5 which should be replaced.

Anyways just not sure what I should be looking at next, just looking for some advice prior to digging into anything.

Thanks

Hmmm I looked at all the fuses and they seem fine. Some are a little darker from use but seem fine, none cracked

I don't have a 3/4 SB right now so I will pick more up tomorrow.

Is it normal I replaced the 3V(F116) fuse and immediately it has some liquid substance on the inside after I turned the game on? It look like little oil spots on the glass.

P.S. Replacing F116 did nothing.

I swapped in a fuse and it darkened almost immediately, pulled it out and tested, 1 resistance(so obviously failed). I will unplug J116, J117, J118 when I get home and see which one is the issue.

Anything else obvious I should be looking for?

Thanks for all the help Randy and others!

Just to update(and if anyone wants to help out, feel free).

Bought myself a breaker and made a 3V breaker for the fuse. Unplugged everything and went about testing. Turns out J112 is blowing the breaker. J112 comes straight from the transformer.

So J112 provides all the 12V power... and this power goes through C30 and BR5? I'm still trying to make sense of the wiring diagrams and everything.... so bear with me.

I am just going to go down and test BR5. How do I test the capacitors? According to the wiki it leads me to believe I am to stay connected to the BR and test from there... is this correct?

Anyways thanks for all the help.

P.S. I have a full set of BR's and Caps to replace on this board so that is not an issue for me. I have no problem with that.

Yeah the bridge rectifier was hooped. I replaced BR5 and C30 and the machine is up and running again with no fuses blowing.

Whew, thanks for the help everyone.