Game: Mr Mrs Pacman.
Condition: No cabinet, purchased as playfield and a box of bits. MPU was toast from battery damage. All other boards of original spec and visually ok.

History:
Story so far is documented here (not necessary to view but will give an insight into the state)...
https://pinside.com/pinball/forum/topic/mmpc-first-ss-second-pin-coffee-table

The issue:
Upon power up the game boots, all displays function correctly. Can add credits and start a game but not in a position to go further as assemblies not installed.

If I leave the game in attract mode it will wait the required time then start the attract sequence. Once the attract sequence has finished all hell happens with the feature lamps. It is like a Christmas tree on acid.

This is with LEDs and incandescent lamps. It is not strobing or ghosting it is like a scene from poltergeist.

After a few minutes all lamps associated with the Main Lamp Driver Board stop working.

What have I tried:
Re-flowed all connectors on all boards.
Tested continuity across boards from on PCB locations.
Ran the game without Aux Lamp Driver Board attached and the same happens (without the Aux lamps staying on)
Ran the game without Main Lamp Driver Board attached and the Aux lamps do as expected in attract mode and seem they would indefinitely.
Ran the Game with main lamp board only one header J1, J2 or J3 attached - still have same issues.
Checked the playfield harness about 5 times for shorts.
Checked header connectors for correct wire locations and colours.

I assume that as the Aux Lamp Board is receiving instruction and acting correctly that the MPU is also behaving.

Does this sound like an issue with the Main Lamp Driver Board or am I barking up the wrong tree ?
What should I try next ?

Thanks,

Guy

The lamp driver board is an AS-2518-23

Is there a process I can check IC's U1 U2 U3 U4.

I have a meter and a logic probe.

Thanks.

The issues described occur even with normal bulbs installed.

Ok, I have been searching this forum and the far reaches of the internet and the only thing I can find that is similar to what I am experiencing is related to multi ball games not having all the balls in the trough.

I assume those issues are because the MPU is looking for those switches to be closed and the code will not proceed correctly unless that is true.

So my next questions...
On these old Bally single ball games what switches would be in a closed state on power up. Playfield and cabinet?

I guess the outhole kicker switch but what about things in the lower cab like the on the coin door?

Upon startup the game runs a perfect attract mode once.

The second pass through the attract mode all the lamps controlled by the Aux lamp board function correctly. One or two of the lamps controlled by the main lamp board will flicker.

A few seconds later the flickering will spread to all other lamps controlled by the main lamp board and they will randomly start turning off until after a few minutes only the lamps controlled by the Aux lamp board remain doing as they should in attract mode.

If I turn the game on, wait for MPU to flash seven times and instantly press the test button the same as above happens but in a much shorter time frame.

Press the test button.
All lamps flash.
On second or third flash lamps start to flicker.
By about the 5th pass only the lamps controlled by the Aux lamp board will be flashing.

I have to rearrange my work space tomorrow so I will try and get things in a position where I can upload a video. At the moment it's all laid out on a table.

Thanks again. I tested the connections by using a multi meter to buzz through from the resistors on the MPU board (R70 to R79) to the corresponding ones on the lamp driver board (R61 to R69). Hopefully this should prove connections are ok.

One thing to add. When the MPU is doing the PIA check on boot. A logic probe indicates a high pulse on Strobe 1 and all the switched lamps flash on and off once.

Yes I have tried swapping them.
In the repair of the MPU I had to replace the socket of U11 as it and the chip were corroded. Do you think I could have an error on my work there?

U10 socket has not been changed yet. But I have made sure with a logic probe that it is seated correctly.

Both PIA chips have been replaced as well as the processor.

Thanks for the time and suggestions. I will dig out the scope over the weekend and give the MPU a review.

- Solved -
I found a video this video where the 555 timer is checked...

Put the scope on mine and it was was acting strange. Replaced the associated capacitor and resistors and got the 555 pulse time to 3.2ns.

When I ran the game the same symptoms as before happened but at a more sedate rate. More in time with how you would expect lamps to flash in attract mode. The order of lamps comming on was just messed up.

I then replaced the U10 IC holder with SIP strip and hey presto all seems to be ok.

Thank you to those who threw in ideas, much appreciated.

Thanks for you input. A voice of reason that kept my sanity.