Need a bit of troubleshooting help. Thanks in advance.

I am refurbing a Blackout. Had been stored safely for years nonworking. Repaired a couple of bad solenoid drivers/swapped the coils. Did the following general refurb:

1) Replaced female side of interboard connector. Replaced all solder on the male side.
2) Replaced solder on all headers on all boards.
3) Cap replacements on power/sound boards.

Everything looked reasonably stable until about a week ago. Then it started resetting/flickering displays/bright lamps. Then the sound died entirely.

I pulled the sound board to learn how to boot it on the bench and noticed that the game is stable without the sound card in it. Okay, so we have a sound board problem. I took a second sound board from a BK that had been stored/working and put it into the Blackout. BK sound board acted exactly the same way - not even speaker hum. And the game started doing the same resets again.

Last night I finally thought to check impedance on the speaker and couldn't get a reading. Swapped in an 8ohm speaker I had around quickly and got some sounds from the BK board. So somehow the speaker had crapped out in this situation but I can't think of how that may have happened. Maybe it's just a coincedence.

So assuming that both sound boards don't have exactly the same problem I'm trying to figure out how the presence of a sound board would cause the game to be unstable. Looking at the power diagram I see that the sound board does not pull power through either of the BRs nor through the power board. It gets AC directly off the transformer but it does come off the same 18.7vac winding as the logic supply. Could the sound board be somehow pulling too much and causing logic voltage to drop even though they're both coming right off the transformer?

Any suggestions are extremely welcome!

On the power board I replaced all solder on every connector and replaced all caps. I haven't touched the regulators yet. All fuses are proper as that's the first thing I always do before I turn a game on. Honestly I wasn't even sure if the idea that the sound board could pull down the main power supply was feasible because they're both powering directly off a transformer winding. It does make some sense, though, tracking back to the common source.

I'll replace the 40 pin header, reflow the rest of the power board, and may as well replace the 5v regulator. Certainly can't hurt to do those things. Maybe clean the fuse holder too. If that doesn't do it I'm assuming replacing header/repinning on the power lines all around?

Interesting result here. I put the original sound board back in. Put the temp 8ohm speaker in to test the sound. Not only is the sound board 100% now but the game seems to be stable. I didn't cycle any connectors except those on the sound board putting the original back in. The only system change is the temp speaker.

Is it possible the original speaker has been just about to die all along and was causing the sound amp to pull too much current to drive it? What sort of reading would I take on that speaker to support that theory? I can't seem to get any sort of useful impedance reading from it. 4ohm speakers in other games are all giving me around 3.7ohms taking the same measurement.

Yeah, I need to triple check those fuse holders to be sure they aren't shorted somehow. And the 5v regulator could be weak, too, so it doesn't take much to pull it down.

Ah, that didn't last too long. Play testing turned out some surging on the lights (both GI and controlled) and display flickering. No resets anymore, though, so at least we're past that. Looks like I do still need to do more work on the power chain. Next up is new BRs and new big filter cap. Since it's not resetting anymore I'm a little less suspicious of the 5v.

I replaced the sockets on the sound board but haven't touched the sockets anywhere else yet.

Is the next recommended step more replacements on the power board or replacing those sockets?

Okay, update here. I have replaced all of the scanbe sockets and the male side of the interconnect. Actually bought a Hakko 301 to speed it up. Nice tool but transfers a lot more heat faster than I'm using to using.

On the driver board one pad was lifted on the female interconnect. Looks like it's 2p-5. The problem is that I can't find 2p-4 or 2p-5 in the schematic to see if anything needs to be remediated. Can someone verify for me that 2p-5 doesn't actually go anywhere?

2p-5 (resized).jpg

Looks like that is correct. I put the board back in and this game is nice and stable now. A bit of playfield adjustment and this project is a wrap. Thank you for the advice, Schwaggs. Much appreciated.