I'm trying to Bring a Baby Pacman back to life. I just managed to repair the MPU, thanks to various suggestions here on the forums.

So, the vidiot board boots, the MPU boots, and there is a light show on the playfield. On the monitor, I can display a bar test and display a communication test. However, the two columns of numbers do not match up. Do these numbers actually provide any useful information?

I looked at the W-1282 cabinet diagram and did continuity tests between the vidiot's J1 connector and to wherever those connections ended up (J1 and J2 on the MPU). All that was successful--there were no dead or disconnected wires.

Then, I tested pin connectivity between the connector and the pins on the boards (vJ1, A4J1, and A4J2). All those connectors made contact with their pins.

So--is there something I should try or test for next?

Thanks

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I've checked the vidiot J1 connector, and the MPU J2 and J3 connectors. I didn't come up with anything amiss, which is why I'm scratching my head on the issue. I was hoping there would be some sort of chart available that listed what the communication test numbers mean. All I understand from them right now is what the "good" reading is (01,02,04,08,10,20,40,80), and anything else is "bad".

The game boots to attract mode, and the playfield gives a light show. The startup sound plays, and if I press the sound test button, that also plays. I can also cycle through the service modes with the service button on the coin door.

The coils fire when the game starts up, but they blow the 1amp fuse on the playfield--but that's a separate issue I need to work on (unless you think that should come first?)

I don't actually press start--all I'm doing is turning on the power.

However, I didn't try putting in a new fuse since after repairing the MPU.

I turned it on with a new fuse and it seemed to power up without blowing the solenoid fuse on the playfield. On startup, the two saucer kickers near the top of the playfield kicked on. None of the other solenoids triggered. I don't have any balls on the playfield at the moment.

[edit]: I went through the solenoid test. It looks like all the solenoids on the test were energized one by one successfully without blowing the fuse. I'm guessing the problem was somehow related to the MPU with its broken/crossed traces at the time?

So, it looks like the MPU/vidiot communication issue is next on the menu.

The switch target solenoids do not fire on startup. Only the upper saucers do. Putting a ball in the outhole saucer doesn't seem to change anything. However, all the switch target solenoids fire one at a time when going though the solenoid test cycle. Unplugging A4J2 on the mpu does not make the drop target solenoids fire on startup.

No luck with the communication tests. Unplugging A4J2 on the mpu yields a blank communication test screen (no numbers appear).

Unplugging A4J1 on the mpu prevents me from bringing up a communication test.

Unplugging J1, J2, and J3 on the driver board does not affect the communication issue.

The lockbar didn't appear to be shorting anything--open or closed.

As long as the drop targets were up, there were no closed switches in the switch test. Testing each switch one at a time registered the correct switch. The 4 flipper buttons did not register during the switch test (they are not listed on the switch test chart in the manual).

I replaced the U7 PIA, but there was no change.

Yes, the vidiot board gives all 10 flashes. It produces sound. The video test button displays the color bars screen. The diagnostic button on the coin door displays the diagnostic test screens.

Does anyone know what the communication test numbers mean? Do they correspond to anything? certain pins on connectors, perhaps?

Woohoo, got it working!!

Long story short, the cables/contacts were fine. The problem was that there was a broken trace on the vidiot board off of U1 on pin 13. Once I repaired that, the game booted up.

During the course of checking and triple checking connectivity, I put together this chart and ended up figuring out with reasonable certainty what the communications test columns and numbers corresponded to.

baby pacman mpu-to-vidiot communications test chart-736.jpg

Under the Vidiot/MPU columns, I notated which connectors and pins were used for communication. Also, the corresponding resistors ("R") on the boards, so you could test continuity from the wire, through the connector, and onto the board.

As for my particular problem, here's where the problem was:20141024010642973-circled.jpg

It was easier to see when held up to a light:20141024010731094-circled.jpg

The repair:20141024011709836-circled.jpg

And the game up and running 20141024013507730.jpg20141024013518878.jpg

There's still a number of things that need to be fixed, but I'm thinking those will be fairly straight forward now that these difficult problems are out of the way and the game is now actually fully booting

So far, I've only made it to the second map. The ghosts on this machine sure do move faster and act "smarter" than on other pacman arcade games I've played in the past.

Cool, thanks for the tips