Hey everyone,

I somehow messed up something on my MPU, and now can't seem to figure out what to do next. Any suggestions welcomed!

The short story is, I replaced the switch-stacks on my pop bumpers with all-new switches, and they weren't reacting properly. I was digging around in there to adjust them, and then while rolling a ball around to see how the pops reacted, I happened to notice that other switches on the playfield weren't functioning. Bottom row of switches is out.

Reading Pinwiki (http://techniek.flipperwinkel.nl/wms11/index3.htm#switch), I determined that I likely shorted the switch matrix to the 50V. Lesson learned, turn off the game before fiddling around with the switches. Ok.

I got some replacement ICs, along with sockets, and replaced U30, U39, and U38. U30 and U39, I got 4011s; U38, I got a W65C21N6TPG-14 from Great Plains, which they say is a direct replacement for 6821: https://www.greatplainselectronics.com/proddetail.asp?prod=W65C21N6TPG-14

Turning on the game, now, sometimes I get an awful squeal (that initial squelch when you turn the game on and everything's fine, but it doesn't stop...), but usually will just get a U38 PIA Failure notice.

I thought perhaps my soldering was bad, but I re-flowed all the solder at U38, and it all looks good. The IC looks to be seated properly. Still a U38 PIA Failure.

Did I blow something else up when it shorted?
How do I go about diagnosing what the problem is?

Thanks in advance.

Bumping this thread.

I uninstalled the socket, and put the U38 in direct. Re-soldered. Still getting a U38 failure.

Anyone know, what else could cause the U38 failure?

Thanks for the reply!

..."tone out?" I think that's something to do with a logic probe, but I'm not sure how to use it properly, and how I'd go about figuring out what to do.

Any guidance toward help on learning this welcomed! I'm about at the point of frustration that I'm looking at repair-people, but I'd love to do this myself...

I've given up. Gonna delete or archive this thread...I gave in, and sent it off to be fully repaired by a pro. As much as I'd like to be able to do this stuff for my pride, I want to get Space Station playing even more!