Game is completely playable, but has some lighting display issues I'm trying to troubleshoot.

The problems:

- In attract mode, the lights don't sequence the way they should. First video, my machine (Half way through the video, I switch to lamp test mode to show that all the lights are working.) Second video, what a Baby Pac-Man in attract mode SHOULD do.

- One of the under-playfield fuses (see photo) blows immediately on start up, but game is playable anyhow (with wonky lights).

- Unrelated to the lighting (I think), but the tilt mechanism doesn't work. Plumb bob is there and is wired up, but doesn't do anything when shorted.

I'd appreciate any help in tracking down the problem. Thanks!

blown-fuse.jpg

Great info. Thanks!

I removed and replaced the 3rd row N diode -- no change. All lamps were flashing in lamp test even with the N diode pulled out.

Retested all lamp diodes with DMM and nothing looked bad. .0L one way, ~0.5 the other.

Did a quick DMM continuity test from all the lamp wires (where they attach to the lamp) to the ground. No apparent tones/problems.

All the wires/diodes appear to be firmly attached underneath.

Worth disconnecting connectors from the driver board to help isolate the problem?

How do you test if a lamp socket is bad/shorted? (or did my continuity test cover this already?)

Do you see what you should with the communication test?

You mean this test screen? Looks OK according to the manual.

comm_test.JPG Screen_Shot_2013-06-03_at_2.56.16_PM.png

I completely disconnected the lamp driver board to make sure it wasn't affecting things.

If I set my meter on continuity and clip a lead to each side of the blown fuse, I get a tone. That's not supposed to happen if the machine is off, right? If I remove the other fuse (the good one), the tone goes away.. so those two lines are definitely crossed somewhere.

Hm.. So what's the best way to isolate circuits and narrow my search?

Could I desolder each lamp wire one at a time until the DMM tone stops?

Remove all the lamps and retest the diodes?

Thanks for the help!

I've had the game for 8 years or so. The lights used to work fine. Can't recall exactly when things went bad, but it may have been the last time I moved (a couple years ago). The tilt never worked.

Just bought my first full-size machine which motivated me to learn more about pinball repair.. and fixing my Baby Pac-Man is turning out to be a great learning experience.

There were three lamps out that I was able to narrow down to a driver board issue. Fixed the problem yesterday by replacing the two related SCRs.

Now that all the lights come on, it's just a matter of finding the short.. and fixing the tilt. =)

Woohoo! Found the short!

I was just about to start unsoldering things when it occurred to me that maybe the problem is not that a wire/lamp is shorted to the ground.. but maybe the ground from one fuse/circuit is shorted to the other. I inspected every inch of the stapled ground line and finally found the problem hidden behind the drop target assembly.

There are two ground wires running across the playfield here.. I traced them back and realized that they lead to different fuses.. but they were touching. Separating the wires got rid of the short.

Weird because it didn't blatantly look like those wires were intended to be spaced apart. There was no staple holding the bottom wire away from other. I saw a little nub of what might have been a staple once, but there was no second hole in indicate that a staple used to be there. I'm guessing it was mis-stapled in manufacturing and eventually (30 years later) the half-staple gave way.

I really appreciate when people document their pinball repairs, so I posted a video in case anyone has the same problem in the future.

short1.JPG short2.JPG

I think the hard part is done, the attract sequence plays as it should, but I see some of the lights aren't activating.

The lamp diodes test OK. I know the lights are good because they lit up prior to fixing the short. I'm guessing that I need to replace more SCRs on the driver board. Thoughts?

Thanks Marc. Your A/B phase info was a big help.

Just got done swapping out 5 new SCRs on the driver board for those lights that aren't working. Didn't help. Diodes still test OK.

I tested continuity between each pins and it's related SCR. All tested OK. Didn't bother to resolder it.

Went back and checked the obvious.. which, in hindsight, I should have done to begin with. I must have loosened a bunch of things while hunting down the short.

- one lamp was blown (was working fine 24 hours ago *shrug*) — replaced
- the ground line solder had broken free from one lamp bracket — re-soldered
- one lamp fixture was not solidly connected to one of the terminals — reseated

.. and ALL the lights work! Even went back and replaced all the dim bulbs to even out the appearance. Thanks again for all the advice!

Now to give it a good cleaning then figure out the tilt issue. Does the tilt work on your Baby Pac, Marc?

baby_pac_FIXED.JPG