To add... I helped Aphex bring this home and set it up. I think the voltage was on J209, not J207... but I’m not standing at the machine at the moment.

What do you suggest we should be checking?

Measuring 12v does not rule out the ULN2803 at U20. All the output lines of U20 are pulled high to 12v through a 1k resistor. The ULN will pull that line down to 0v when it drives it and let the 1k resistor pull it back to 12v when it is not driven. I don't see a huge mark on the upper part of U20 , but that doesn't look like real physical damage. Do you have continuity between pin 9 of J207 and pin 11 of U20 (red line in pic).

I see corrosion on the battery post , any corrosion below it at all ? no matter how small? Pictures look clean except for a blue glow in one of the pics , but it looks like a camera reflection.

On the picture, ULN receives the signal for column 8 on pin 8, in yellow, outputs it to pin 11 , the red line. Both green marks are the power of the chip, which is far from the mark on the upper right. If you have a logic probe, you can verify easily both pins 8 and 11 of the ULN. You might be able to test it with a multimeter only but most meters don't react fast enough to really see a change, but some do. Analog ones would. These pins are constantly driven at a regular interval. The ULN inverts the signal as it drives the output. On pin 8 you should measure 0v until it receives a 5v pulse. On pin 11 you should measure 12V until it pulses to 0v quickly.

No reason to type more than as already been explained, just read this post:

https://pinside.com/pinball/forum/topic/terrybs-guide-to-logic-probes#post-2514877

Most likely U20 really is faulty. It's a very common part and should be fairly easy to change , especially when you don't care about salvaging the part, for the rookies cutting the pins and removing the chip, to then desolder each pin one a time by pulling them out yields the cleanest results. Rule of thumb , if you change an IC , install a socket.. It costs cents and can save headaches down the road.

16.jpeg

A better pic of his U20 is attached.

If he can’t do that himself, I’ll check in the next few days and get back to you.

No corrosion evident on the board. Could be some under the battery holder, but it hasn’t migrated downwards at all.

I have a logic probe. Not sure I understand what you’re asking us to do, but I’ll give it a try.

24FD2EEA-C39A-4411-9923-F04FA35486F4 (resized).png