Help with Baby Pac


By fattdirk

6 months ago


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#1 6 months ago

I stumbled upon a baby pac and lo and behold it doesn't work!

I ended up putting an Alltek MPU in it so I could at least get the vidiot working before repairing the MPU. I'm getting good voltages on at the test points on the power supply as well as the test points on the vidiot. The first power up only gave me 4 flashes on the Vidiot. I removed all the roms and verified them in the burner and found U11 was bad. I burned a new one and replaced it. The vidiot would then flash 8 total times.

Looking at the pinrepair guide, it sounded like the TMS9928 was bad. I ordered a new one and replaced it and ended up with 9 flashes. I ended up ordering new video ram which should come in this week. I swapped the video ram around and tested the connections on the sockets and they all appear ok so far.

I'm just curious if I'm counting the number of flashes correctly on the MPU. This is my first attempt at repairing a baby pac so I'm not sure. I just get a bunch of garbage patterns on the screen after it boots. If I press the video test button once it has no effect, but if I press it twice I get a nice color bar test screen.

Pressing the test button inside the coin door cycles thru the light test and solenoid test but nothing happens on the screen.

Can someone that is more experienced with these boards take a look of my video and tell me if I'm missing the 10th flash?

The 2 second pause between the 8th and 9th flash is what seems odd to me.

» YouTube video

I'm planning on replacing the connectors this week when I get a chance. I was hoping to get the vidiot to flash 10 times first though so I could see the communications test.

#2 6 months ago

You will want some other replies. I'm using the older Rev. A Vidiot (plays the startup tune without stuttering, seems to have less video noise than Rev B.). You are getting a long pause before the ninth flash. Mine does that long pause before the tenth and final flash (the Vram test).

#3 6 months ago

I have a rev B vidiot board in mine, and while mine does play the stuttered sound on boot it actually plays more of the pacman sound than yours does. This isn't my video, but this is how mine sounds:

» YouTube video

He also gets ten visible flashes on his as well.

#4 6 months ago
Quoted from Biffbar:

You are getting a long pause before the ninth flash. Mine does that long pause before the tenth and final flash (the Vram test).

This is where I'm confused, from other videos I've seen it looks like the 10th flash has the long pause not the 9th.

#5 6 months ago

Welp - she's alive! I just want to document this in case someone has a similar issue in the future.

It ended up being a bad socket on U10. I figured this out because I was missing the 5th flash on the vidiot. Now how I figured that out is the interesting part. I found a video of the vidiot booting up properly:
» YouTube video

I slowed it down to .25 speed and took my video and queued it up right at the start of the first blink also at .25 speed. I then started the video with the good sequence and then started my video right at the first blink and watched them basically overlaid. I saw it was missing the 5th blink.

What's confusing is you would think it wouldn't miss a mid stream blink. It kinda makes it impossible to troubleshoot by just counting the blinks unless you're super familiar with the pattern.

I buzzed out the pins on U10 and it turned out the socket was flaky. I knew it was the socket because I had already verified the roms earlier although I did put it in the burner and verify it for good measure while my solder sucker was heating up.

I still have a few bad lights and switches but I believe those are due to bad connectors which I will be replacing this week. Next step will be to plug in the original MPU after the game is working 100% to get it up and working so everything is original.

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