It stopped doing it as soon as I started watching it. But just wait, I'll catch it in the act. >_> <_<

They sell "broken" Ender 3 printers on eBay for like $75 shipped. I ordered two. One had a bad board (a $40 part); one had a bad Y limit switch (a $3 part) -- so the actual cost per printer seems to be around ~$100 if you're familiar with how they work and can identify which parts aren't working.

I traced the alarms back to Breaker #8 in Panel #2 (the detector tool actually worked okay this time). I disconnected the breaker and verified that killed the circuit. I swapped the alarms and updated the map of known breakers with this new information:

No great surprise, but the blue boards seem about the same as the red boards and have the same problems:

The genuine article is not a JST-VH 4-pin connector -- the connecting clip is a little different, and there's no hole in the housing for (unused) pin #2. However, the pin size and spacing is right, so you can cut the connecting clip off a JST-VH and melt one of the pins out and the connector will fit well enough.

I bought an oscilloscope and tested the speed signal of one of the new red boards once it arrived. The scope showed the perfectly sensible signal I expected, and the signal came off the board fine once I hooked it up. So maybe the first couple boards were legitimately bad?

This connector has a 4mm pin pitch, but I had a great deal of difficulty finding a likely-seeming bare connector with a 4mm pitch. After resigning myself to a Digikey quest for a connector that will fit a board on T13692, which also has a "4mm" pitch I realize the pitch is probably not 4mm but 3.96mm -- a wonderful pitch for which many connectors are readily available.

Here's the updated lightbar:

Here's my nice safe smoke detector power adapter:

There doesn't seem to be anything mechanically wrong with the toy, although the motor and gearbox don't seem to be accessible without breaking something.

The capacitors on both boards arrived pretty banged up.

String Shelf

Turny Thing

Motor Drivers

Couple of years ago the furnace wasn't working so well. Light comes on, three reds. Pressure switch stuck open. I take off a panel, pull the pressure switches. The contacts close properly. No clue what's wrong. Call an HVAC guy. He's pretty busy. No problem, we got plenty of sweaters. Ha. He makes it out early the next week.

all my drains are belong to PVC

... condensate drain ...

...there's enough absorbent material underneath the sink...

(You don't actually need a leak detector, I think there's enough absorbent material underneath the sink to last a long while before it damages the floor)

Here is my bathroom sink. The right-most pipe coming out of the wall is the condensate drain from HVAC. The tailpiece is most definitely 1 1/4 and the rest of the piping is 1 1/2, at least to the naked eye.

I can't see a way to make the trap be any less garbage than it is because the 4" flanged tailpipe (the shortest flanged 1-1/4" tailpipe I could find) plus an additional 8" of tailpipe underneath it (the only 1-1/4" branch tailpipe I could find, which is only available with a slip fitting) means that the bottom of the lower tailpipe is super low. It looks like I left an extra 6" of flexible pipe on the drain side for fun, but that's just the rigid bottom of the tailpipe plus the minimum bend radius without making the flexible pipe start to crimp -- the bottom of the tailpipe is like 1-1/2" below the black plastic retainer clip.

A few more thoughts:

Since there's no fresh water supply to the dehumidifier I don't think there's much benefit to an air gap, as there's no way backflow could ever contaminate a supply line. A clogged sink drain could possibly drain sink water out through the dehumidifier bucket, but the top of the drain line is only ~1"-2" below the top of the sink so it would overflow the basin onto the floor before very long anyway.

My terminology might be wrong throughout this but a couple thoughts:

Other options I explored and rejected: