Hello.

I was having the classic Mist issue where the magnet would run back and forth and the mist ball would not populate.
This thread was the exact issue I was having:

https://pinside.com/pinball/forum/topic/bsd-ball-on-magnet-issue

After reading through that thread, I ordered the caps and the inductor mentioned in it with the intention of replacing L1, C7 and C10 on the 24 opto board. While I was waiting, I cleaned both ends of the opto switch with q-tips and window cleaner. That got switch 82 to work in test, and Mist would work perfectly for about 1 game, then the issue returned. This worked a few times, but always reverted shortly.

Today I got the caps and the choke, replaced them, and also re-flowed all the header pins on the 24 opto board.

Now at bootup, the problem remains, but after about 2-3 minutes everything seems to work just fine, and as long as the game stays on, everything works just like it's supposed to. As a test, I shut the game down and let it cool, then started it up and immediately put it into switch test on 82. It started off solid "open", then after a couple of minutes started "chattering" closed, and eventually settled down and started working correctly.

If I do a "quick reboot" just letting the game sit off for a few seconds, it comes back on working fine, which makes me think there is something that needs to literally "warm up" to an operating temperature in order to work properly. Any idea what I should be looking at?

More data: at "cold boot" I am seeing approximately 15VDC at the header pins of J118 on the driver board with the connector removed, so no load. For a 12V unregulated line, this seems fine to me.

I also saw this thread: https://pinside.com/pinball/forum/topic/bsd-dracula-mist-opto-intermittent-
and this one:
https://pinside.com/pinball/forum/topic/aligning-bsd-mist-optos

But in both cases the OP never followed up as to what ended up working.

Thanks!

Update: After a couple of hours, it looks like the long opto has quit again. I have verified that the 15VDC that I was seeing at J118 on the driver board is making it to the opto board, and using @zaza's resistor test as outlined in this thread: https://pinside.com/pinball/forum/topic/bsd-mist-woes-long-beam-opto , I get a "jittery" signal when shorting the pins on J1 and J2, but I get a solid signal at any time by using a diode to short pins 1 and 3 on J3. This suggests to me that the wiring under the playfield is very likely fine. Now I'm looking at the connectors on the board, and really, really dreading having to replace the opto (I am mostly concerned about trying to get it aligned, and I am also finding some conflicting information as to whether the transmitter and receiver are a different part than a "normal" opto).

Update: Replaced the 24 opto board with a Homepin board. Right at boot the switch worked, and an hour or so into testing it looks solid. I'll work on the old board and see if I can restore it, but it appears that the problem has been solved.

Not yet. Since the replacement board worked perfectly, repairing the old board got a severe demotion in priority. I do plan to get to it eventually, and I will probably end up shotgunning it, and just replace everything until it works.