It might be the Mpu board or the Master display board. Did you want help toubleshooting this?

First off, brilliant idea with the color choice in the displays! I think it's the best use of color LED displays in an older pin I've seen.

Judging by your before and after pictures, I wouldn't suspect the CPU board since you would have had the same symptoms before you installed the LED displays. The first thing I'd look at is the display driver board; while it may be new, I'm suspecting it's faulty.

Do you have a logic probe?

I see the problem, and since you have changed the driver board then its for sure on the MPU board. If your not ready for board soldering then there's no reason to get the logic probe. Your problem may be U44 or an SCR resistor pack, but either will require soldering.

That's what I like to hear.

Not at all.

Do you have a schematic for the game?

If you do, on page 55 displays 3 and 4 segment G goes back to U9 pin 17. U9 is an UDN7180 driver and the data sheet show that pin 2 connects to pin 17. U9 pin 2 goes back to 4J1 pin 2. 4J1 pin2 goes to the MPU board on 1J3 pin 2. This wire is blue/red. You need to go into display test and stop on a number that uses G segment. For example 2,3,4,5. Then use your probe and check the blue/red wire for low pulses. What do you have?

Yes your problem may be SRC9 or U51.

So it not pulsing, and thats to problem. Scr resistors are to pull up the signal to 5 volts or a high and the PIA chip drives it low. If you turn off the power and do an ohm test on scr 9. Measure resistance from pin 1 to 2, then pin 1 to 3 and so on. You should read 4.7k ohms each time. Test this and tell me what you find.

I enjoy doing this, now the white dot is pin 1. It should have 5 volts when the power is on. The blue/red wire should go to pin 8. Pin 10 is ground. Since nothing at pin 8, you have found your problem. These are .40 cents at Big Daddys.

I wanted to show you how I followed it from the problem (the displays) back thru each board and connector to the bad componet. This way you will have a better understanding, and be able to find problems on your own in the future. Read Terry B soldering guide, then make the choice of sending it out or fixing it yourself.

That is a very good idea. Find something small like a signal transistor and unsolder it and resolder it 5 times. If you can do this with out damage to the traces, then you are ready for the real thing. And when you do the real thing you can cheat by cutting off the part. Then unsolder each pin with a solder sucker. Take your time and follow Terrys guide, you will be fine.

One more thing I forgot to tell you is that when you replace the resistor pack is they don't make them anymore. The original packs had 8 resistors and 8 capacitors and ten pins. Pin 1 positive 5 volts 2-9 resistors and pin 10 is ground. The new bussed resistor packs don't have capacitors any more, so a ground pin is not needed. They come in either 9 or 10 pins, if the one you get has 10 pins you will need to remove the 10th pin with wire cutters so that it can't touch the solder pad. Remember pin 1 has a dot on it just like the MPU board has.

Buy yourself a beer and enjoy.
Red and blue displays look great in PINBOT.

I didnt read this entire thread (up w newborn n not a lot of time), but a faulty pull up resistor SIP pack causes this problem. I've got like 200 of them if u want me to mail u one.

edit, just glanced up n saw this had been answered/fixed. awesome!