I’ve recently acquired an Earthshaker and I’m currently sorting it out.

I have an issue with the display where on the lower display the top right corner of every digit is locked on.

I’ve swapped the display and ribbon cable from my Whirlwind and have determined it’s not the display or the ribbon cable.

So… on to investigate the MPU - from what I’ve initially read the 74154 and or PIA could be at fault, MPU is clean and no battery damage, even went over it with a UV black light. I have not removed the MPU yet but when I do I will check for bad traces / cold joints and other wacky ness.

Is there anything else I’m missing here, I’ve attached a few photos.

Thank you for your time.

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I got the MPU out today to clip out the battery holder and replace with a battery board.

The traces that run under the battery holder from the display connector and resistor packs all seem good, I tested continuity from the display header and each pin seems to reach one of the two PIAs under the battery holder.

I’ve probed pins 1-17 on the 74154 and all of them except pin 12 are pulsing.

I have a 74154 and a PIA on the way from Marco, I’ve attached a picture of that section of the MPU.

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I replaced the PIA at U41 with a socketed one and unfortunately it didn’t fix anything and was also a huge pain in the ass to get out… game still works - I generally don’t like shotgunning parts but took a chance since that PIA drives the ‘a’ and ‘b’ segments of the screen.

I will replace the 74154 as well but just waiting on some transistors.

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Thank you PinballManiac40 and DumbAss -

So if I look at the schematic again, I should question the PIA at U42?

Also good idea - I will test the display and cable in the Whirlwind.

DumbAss - Thanks again, I was getting lost by assuming everything was generated on the ribbon cable at J22 on the CPU board.

I'm trying to show my work - I think I see what you mean, J5 doesn't look like its connected on the CPU schematic and looks like it is coil and solenoid power on the aux power driver and interconnect board.

U51 attached to 1J3
Screen Shot 2022-08-10 at 9.06.52 AM (resized).jpg

J5 and J3 connected to display two
Screen Shot 2022-08-10 at 9.14.16 AM (resized).jpg

Edit: This makes more sense if you look at the MPU, this picture was taken right after I bought the game and I have since removed the batteries and replaced with a battery board.

1J3 connects to U51 on the MPU and on the other end of 1J3 is J5 on the display board.

Screen Shot 2022-08-10 at 10.48.52 AM (resized).jpg

Update: Tried the Earthshaker display and cable in the Whirlwind and it works with no locked segments.

So… it looks like I’m at least replacing the PIA at U51, I’ll order another one and replace it with a socket.

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I replaced the PIA at U51 with a socketed one and that fixed it, no more locked on display segments.

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