AE

Let's check out a Bally pinball MPU board tester from 1976.
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[@spacedock873]

A box only an enthusiast could love! 😂 I'm guessing that the two PIA's on the main board are multiplexed in some way as it needs five on the tester to check them. Good luck replacing all the pins on those connectors - as has been mentioned previously, you have more patience than I! 😀

[@g4z-kb7ct]

Nice thing to have when they are working but nowadays the faults and repairs on these boards are well known and relatively easy to fix. Years ago I had one of the full large suitcase Bally testers that can test all the boards.

[@Anangelspath]

I thought you were going to say have a look under the skirt nice machine

[@waynegram8907]

Can you give a theory lesson about how the MPU Tester is generating the Test codes? the MPU Testers ROMs must have a lookup table of test codes?