Baby Pac Project (trouble shooting)

jfruge

New member
Joined
Oct 9, 2008
Messages
866
Reaction score
1
Location
Turlock, California
Guys, am trying to trouble shoot a baby pacman project I have been working on. I was only getting one flash on the MPU board so I sent it off to get fixed. I now have it back in the game. I am getting 3.5 to 4 flashs now. From what little I have read I should be getting 6.

Thoughts?
 
Just what I needed. So it looks like the problem is still within the MPU board and its failing the the self test of U11.

I have an email into Chris (who repaired the board).

Thanks,
 
Last edited:
If it was working for Chris it might just need the chips reseated. Also, you should verify that you have good power going to the board - power problems can cause all sorts of odd problems...
 
Check your connectors to the mpu board...the ones on there are crap and will give you bootup failures...If you had someone reputable repair them which you did..the only other issue would be you have issue with the connectors themselves..they often get crud on the pins from old battery acid leakage and overall wear and don't make good contact...

Of course it goes without saying you need to verify your power supply is putting out what it needs to and within the range it should be...
 
Ok, after looking @ this again it looks like I am getting all 6 flashes.

power on = flicker, one flash, two flashes, three flashes....then a long pause before I get the 5th (relay noise) , 6th flash. then I get some light flashing on the playfield (over and over) but that is it.

FYI,
 
ok, it looks like I am getting 8 flashes on the Vidiot board. 2 short of all systems go!

Learning more all the time about this game!

Fun Fun,
 
update!

I tried a 2nd Vidiot board. this one seems to boot to all 10 flashes. I still have no video out and no coin up. I can get a rug type pattern if I hit the video test swtich but that is about it.

It seems like I am getting closer and its sorta comming to life. I get more flashing lights on the palyfield now :) :(

stuck @ this point.

John Fruge
 
http://www.pinrepair.com/bally/babypac.htm

No Video or Bad Video.
Even though a Vidiot board gets 10 flashes on the diagnostic LED, it can still have problems and not work. A common failure is to have absolutely no video output at all. Assuming the 13" monitor is working, the first thing to suspect is the TMS9928 chip at U16, as this 40 pin chip is very problematic. If this chip is having problems, often the video will be distorted or won't sync properly. But you will usually have some kind of video.

The TMS9928 chip outputs the video signals directly to two video amplifiers, LM359N at U18 and U17, and then goes to the output video plug at J4. If either or both LM359N chips are bad, you will either get absolutely no video, or video that won't sync. These video amplifier chips do fail (just repaired a Vidiot board where the TMS9928 was fine, but both U17 and U18 LM359N chips were bad).

Also note the video signal passes thru a number of resistors around the LM359N video amplifiers. If the colors are strange or won't sync, check these resistors. In particular there are three 100 ohm 1/2 watt resistors than often go open (R89, R97, R102). You will have to remove one end of the resistor from the board to test with a DMM. Also the three 3.9k resistors (R101, R96, R88) mounted just above the 100 ohm resistors should be checked too.

The pots for the colors and sync also go bad often. The green and sync are 10k ohms, and the red and blue are 2.5k ohm pots. Replacement is a good idea.

Video ground is another problem. There is a large ground plane on the front and back side of the Vidiot board. Make sure these two ground planes "buzz out" and have continuity with each other (a small jumper may be required to ensure this). Also if the video is over-saturated with blue or red, there may be a problem with the video signal ground at J4 pin 2. The factory often has a capacitor going from Vidiot J4 pin 2 to ground. If red and/or blue are over-saturated, replace this resistor with a jumper from J4 pin 2 to ground. This should fix the saturation problem.

Also check the two 74LS374 chips at U1 and U2 as these are problematic too, though this may not reflect directly in the video signal.
 
Update!

Very cool update! I used the ideas in post 10 and swapped out the U16 chip on the 8 flash board to the 10 flash board... I now have video and coin up. I can play the video game and move to the pinball and back to the video part... sweet. I don't have any sound so I guess that is next.

Thanks again for all the help.

John Fruge
 
Here are 2 pic's of the now working game. I have found out that if I connect a extra speaker to the board output the sound works fine. looks like I need to trouble shoot the harness / speaker setup.

I did get to play a few games tonight!

Fun Fun,

John Fruge
 

Attachments

  • baby-pac-9-5-09 003.jpg
    baby-pac-9-5-09 003.jpg
    97.2 KB · Views: 24
  • baby-pac-9-5-09 004.jpg
    baby-pac-9-5-09 004.jpg
    92.2 KB · Views: 20
Thats awesome that you're starting to get this working. My buddy has this game and let me tell you from personal experience that game was not only a son-of-a-gun to get working but also to keep it working once it was fixed.....
 
The volume pot for this should be located just inside the coin door...they are notorious for going bad or the wires may have come loose..should be a simple fix since you know your sound is there...check there first.
 
It looks like the sound problem is one of the two speakers. I by passed it and the other one works fine.

Fun Fun,
 
The volume pot for this should be located just inside the coin door...they are notorious for going bad or the wires may have come loose..should be a simple fix since you know your sound is there...check there first.
My baby pac has a volume pot on one of the boards.

Glennon
 
I lost video sinc. Anyone know where I can get these new parts ? 1 x TMS9928 2 x LM359N.

I just started searching but so far no luck on finding both @ one place.

Thanks,
 
Back
Top Bottom