It's stable.

The transistors and diodes all seem to test ok. The capacitors appear to supply steady voltage, and were already replaced by a prior owner. I'm not sure how to test the variable resistors.

So, since I wasn't getting anywhere with this, I took an old computer power supply and hooked it up to the MPU just to see if the problem was with something in the cabinet. The LED still locked on.

Then I started going through testing components again, and found two diodes that tested bad--1N4148 diodes at CR6 and CR49. The other 1N4148 diodes seemed to test ok. I'm not sure how I missed them the first time around--or maybe they went bad later? I'm not sure.

So, I ordered a handful of those diodes, and am currently awaiting their delivery.

I replaced one of the diodes, but it gave the same bad reading.

So, I ended up removing one of the sockets that looked questionable (it was u19).

https://pinside.com/pinball/forum/topic/best-way-to-remove-a-regular-ic-socket-from-a-board

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Lo and behold, there were 3 broken traces under that socket. After repairing those traces, the two diodes that tested bad were then testing good. As a result of the repairs, the two red jumper wires on the back of the board didn't appear to be necessary any longer, so I removed them.

Yellow arrows point out the repairs I made. The trace with the tail still on it was temporary, and I cut it off after the socket was in just to make sure it didn't go anywhere while I was soldering the socket (since the other end of that strand of wire went through the pin hole in the board).20141009212957244.jpg20141009213830773.jpg

After powering the board, it still gave a locked on LED, however, when I shorted U9 to reset, I consistently got it to flash once.

So, looks like some progress has been made. I think I'll remove the other sockets that look questionable and go from there.

I ended up replacing the sockets for U17, U18, U19, and U20 and repairing broken or previously repaired traces. I think the main problem was the broken traces under U19.

I also replaced the diode at CR44 since it looked like it was a bit misshapen and swollen (but still tested good...better safe than sorry).

After all that, I'm now getting a flicker and one flash consistently.
Progress, finally!

Now I have to figure out why I'm not getting a second flash...

Yellow arrows indicate where I repaired broken traces. Wow, seems like someone really butchered these traces when they added sockets.20141010020922343.jpg20141010024705274 - Copy.jpg

U7 p13 gives off a pulsing signal with a logic probe and reads 2.01-2.05v for several seconds, then settles at 2.12v.

The chips at u15 and u16 don't look like they have been touched and are still soldered directly to the board.

U14 is still using an old socket like the others I replaced. I guess I'll go ahead and replace that one as well.

[Edit]: well, I removed the socket, but all the traces appear to be intact. I'll probably test again and put on the new socket later tonight.

Well, I replaced the socket, put the chips back, and still only one flash.

Then I had the bright idea to put in the original u7 RAM chip that I had, rather than the one I just bought--and--cowabunga, it worked!!!

The board booted with 6 flashes (if I understand, the -133 board in Baby Pacman gets 6 flashes, and the regular -35 board gets 7).

The playfield goes into attract mode!

After all this trouble, it seems almost silly to be hung up on a bad chip for the last leg of repairs

But in any case, this is amazing--finally, some initial signs of life

Unfortunately, I'm not done yet. The game doesn't show up on the monitor. So, I'll have to read up on the vidiot section of the manual next with the communication tests. But considering the vidiot board boots, emits sounds, and shows a color bar screen test, things are really looking good now as far as the board work goes. After the vidiot board, I'll probably take a look at why the solenoids keep blowing the fuse on the playfield, and then try to fix the lamps that aren't working correctly.

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Thanks for all the help getting this board working--it's been quite a frustrating several weeks and it looks like the persistence finally paid off.

Thanks, feels pretty darn good to finally get it working. I learned quite a bit along the way

I did some testing, and didn't find anything that jumped out at me about the communication issue. I started a separate thread for the vidiot/MPU communcation issue: https://pinside.com/pinball/forum/topic/baby-pacman-vidiot-mpu-communication-issue