I will try to remove the anode cap by hand once I can cobble together a tool to discharge the CRT. An flathead screwdriver (with an insulated handle) and an alligator clip running from the screwdriver to the metal chassis should be sufficient to discharge the CRT, correct? (That's what I've seen in almost every video showing someone discharging a CRT.) I'm assuming it's crucial to remove the logic board from the computer before doing any work on the CRT.
As mentioned, I'm mainly worried about the neck board and reinstalling everything. Last thing I want to do is either break the neck of the CRT or reinstall something wrong and let the magic smoke out of something else or, worse, catch something on fire.
As for now, I've made a video depicting the behavior this machine is currently going through. I was able to get it to boot into the ROM operating system, but it instantly crashed as soon as I loaded a floppy disk. When it came back up, it went into a "chime cycle" where the machine would crash (thus chiming again) when trying to eject the floppy. I ended up having to manually remove the floppy using a straightened paper clip.
Here's the video:
Well I did it.... got all three ticking time bombs out! It’s important that first order of business with classic Macs is to remove the PRAM battery! Leaving them in and or replacing them and forgetting them can destroy your classic Mac!!
I swapped an LCIII board into a LCII case several years ago and I don't recall there being any problems with that. FWIW I want to say there's enough spare room that the board's shorter clearance to the fan isn't a physical issue (the fan is held in by clips to the left and right relative to the above pictures). Presumable the other direction (LCII board -> LCIII case) is also amenable, given that the boards are essentially the same in dimensions and components as well as the side notches. You know excepting the spacing difference near the fan which shouldn't be an issue as the LCIII case has space for the fan and the LCII boards leaves more room, not less.
you can see the extra space near the fan here:
My guess would be that you could probably migrate a Macintosh LC board forwards with some caveats relative to hooking up various components and a LCII might fit into the LC chassis. It does look like from the below page that the LC had a larger fan+surround design that might not permit fitting the LCIII board, though and the total lack of the edge connectors might be a problem.
It's also worth noting that the PSU connector moved from the LCII board to the LCIII version IMHO it's a bit of a tight stretch, but plugging the LCII's PSU worked okay.
When my SE battery exploded, many of the traces that were sound-related around the speaker terminal were damaged. I'd check them with the multimeter and make sure there was no damage.
As for the battery, after looking at a few boards, I realized that they put in the two different spaced battery terminal through holes for different sized components. you can use any combination of two to make a connection (as you did).
Lastly, that orange crud did come off my board with some real work.It was in exactly the same place. It was hiding some rotten sound traces that run directly under the battery holder. I would focus my efforts here to find your sound issue. You can see in my photos: