I have the exact same issue on an Eight Ball. I checked the J1 connector, pushed pins in and checked wires but that did not change anything. Is it strictly a repin to fix this or could U20 or another chip be bad on MPU?

Quench I tested this last night: do you measure zero ohm continuity from pin 17 at any display connector, to the MPU board on the top leg of resistor R82 (which is near the bottom of the MPU J1 connector) and with meter on 20 ohm setting I get a reading of .3 Also checked continuity from pin 17 to the resistor and was fine. Logic probe read H.

I also checked the BCD segments at MPU connector

D0 Low
D1 HL pulse
D2 High
D3 HL Pulse

Sorry @quench, updated the post, the test at resistor was high not high pulse. Just mistyped. Does that indicate that U20 is sending the wrong info?

Quench for mine the problem remains after removing J2/J3 from the MPU and J4 from lamp driver

@quench the credit/replay switch does not register (I can coin up but never start a game). When I go in switch test it lists 46 which I guess is really 06 for credit switch. Connection from both wires to the connector is good and I replaced the diode.

For the resistors 80-83 the bottom and top legs do not give a reading when checked VS ground.

Quench aha, seems I went way too low with my resistance measurement. If I use 20k I get
Upper
80=3.35
81=3.4
82=4.65
83=3.36

Lower
80=2.17
81=2.21
82=1.41
83=2.17

Here is the MPU, will also do as tech thread

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Quench excellent! I tested with the dips all off, pulled the 6821 and still get the same readings on R82. So I will find my parts board and check on the caps. Not sure if I have any of those caps on hand other than a parts board. Will let you know what happens.

@quench Thanks again for all your help!. Well I replaced C47 and C53 and the display issue remains. It did fix the credit/replay button so it will start a game now. I did recheck with removing the connectors but still same display issue and resistance is still higher on R82 than the others.

You mentioned there was a 3rd capacitor to check, which one is it?

Quench I measured R38 and it was (20k meeter setting) 3.53 while the surrounding ones were more like 2.1. I checked another board and all the same resistors were all 3.X. Both boards were -35 versions. I did not lift the leg since it was not lower.

I also checked the continuity from the bottom of R38 to pin 8 on U10. Did not have it at first. Pulled this chip and checked. Had continuity to the socket but not when the chip was in. Added a little solder to leg 8 of the chip and now have continuity from bottom of R38 to pin 8 chip leg and socket+board. However still have 44 on the display.

Quench R82 now reads 1.2 so that seems good now.

Will have to check the rest of the socket receptors

R38 measures 3.53 in circuit and 3.50 out of circuit. When I desoldered the leg it mostly came off. The resistors around it read 2.1. So I guess I need a new 2.1k ohm resistor to continue or is it supposed to be 3.3k ohm (based on schematic)? I guess the leg could have been faulty

@quench Thank you so much for your help diagnosing all this!

Since the leg came off R38 I replaced it with a new resistor (not from part board). Measurement across now is 3.3k.

For the logic probe measurements:
U10 pin 8= HL Pulse
Bottom R38= H
Bottom R82= H
Top R82= H
Top C47= H
Bottom of C47 = L
Resistance across R82 is 1.2k

Could it be that the C47 I replaced was also bad? It came off the parts board.

Here are the daylight photos of the board

For some reaon it wont let me select the original size so I did high res which it allowed.

DSC06292.JPG

DSC06293 - Copy.JPG

@quench Great news! I checked each socket on U10 and did the solder trick on each leg, popped it back in and boom....got 00. Could have been a combo of the receptor and the pins were marked up from use. For anyone reading after the fact, I put a little solder on each leg, just enough to coat it and make the leg marginally thicker side to side. That kept me from replacing a 40 pin socket and fixed my display issue.

Also fixed the flippers and all features work. Got some janky light sockets and switch adjustments, but should be smooth from here out.

Thank you again Quench, your help and guidance was the key to getting this Eight Ball over the finish line.

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