Baby Pac Troubleshooting

Reddogg

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I've got an issue with my Baby Pac which started a couple of months ago
when I turned it on for the first time in a about 2 months. During a 2
player game, things started behaving weird and, upon a few resets, I began
blowing fuses (the 6 amp on the power pcb, and one of the 10 amp fuses under the playfield).

Here's a link to my previous post which describes what happened in more detail:
http://forums.arcade-museum.com/showthread.php?p=2081335#post2081335

So I began troubleshooting, and found that if I unplugged the J4 connector on my MPU, then consistently my vidiot blinked the correct number of flashes (10), and I always heard the start up tune, and I never blew a fuse. But, the LED on my MPU did NOT light up or flash. When I did the video test and sound test on the vidiot, both worked fine (all colors showed on screen, and the little tune played for the sound test). The lights on my
playfield also lit up, but the solenoids did not reset. I ran the force communications test, and got no results.

Then, I plugged MPU connector J4 back in, and unplugged J8 from the solenoid pcb. Then, I also did not blow any fuses, I still got the correct 10 flashes from the vidiot, the start up tune, the playfield lights, still the LED on my MPU did NOT light up or flash, and on the screen during the video test I got the color bar image, but this time it was scrolling left to right really fast. And still, the solenoids did not reset.

The next thing I did was remove the MPU pcb and examine it. From what I can tell from the schematics, the +5v is carried to the MPU (connector J4) from the solenoid pcb (connector J8)? After examining the entire board, I did happen to find only one thing visually wrong, a burned up CR52 (next to pin 19 of J4), which routes to pin 15 of MPU connector J4.

So, I began to put the MPU back in, hooked everything back up, and then accidently bumped the interlock, which turned the machine on, and this time with everything hooked up, I did NOT blow ANY fuses, got the correct 10 flashes from the vidiot,the start up tune, and this time got the LED on my MPU to light up, but it did NOT flash. And still the lights on playfield lit up, but the solenoids did not reset. Now, when I do the forced communications test, I just get a black screen.

And that's where I'm at now.

Does anyone have any idea if a bad CR52 can cause things to go haywire like this?

My MPU was working flawleesly for a long while, and is very clean, with no corrosion, so I don't believe that's an issue.

Any help or suggestions on what to try/test next would be greatly appreciated! I know there are several test points on the MPU pcb, but I'm not entirely sure what voltages to look for and where.

Thanks.
 
Last edited:
So, I scoured the manual and did the best I could at taking readings on all of my Baby Pac pcbs (I'm new with schematics). Here's what I am consistently getting with all connectors in the cabinet hooked up:

MPU:
TP3=4.7 should be 21.5
TP5=5.30 ok
When checking connector J4 (unplugged):
PIN12=15.59 should be 11.9
PINS16,17=5.32 ok

Vidiot:
TP1=4.93 ok
TP2=5.18 ok
TP5=7.2 should be 8.2
TP6=11.57 ok
TP7=2.52 should be 5.0
When checking connector J3 (unplugged):
PIN1=0

Solenoid:
TP1=15.25 ok
TP2=5.31 ok
TP7=5.28 ok

Power Supply:
TP1=0 should be 6.5
TP2=0 should be 230
TP3=15.78 should be 11.9
TP4=0 should be 6.5
TP5=0 should be 43

***I have no idea why my power supply only gives a reading at TP3. I tried all test points several times, and these results are consistent.***

I still get a solid LED on MPU.
Still get power up tune to play.
But, now the Vidiot is only flashing 8 times, and stays solid on the 8th flash.
I still get nothing on the monitor, just a blank screen.
No longer blowing fuses with everything connected.
All fuses are correct and brand new.

I'm not sure where to go from here, and what these readings are indicating as far as failed parts go.

Anyone have any ideas?

Thanks a bunch!
 
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