Regarding the monitor:
It's hard to see the chassis so I blindly took some flash photographs with my phone to get a better look and noticed a loose connector (the grey one in this photo)...
photo-5.JPG
And another grey one which connects to the anode was just the same.
I braced myself and pushed them in firm, and I think that's now sorted it. The screen seems better than ever. It always used to wobble occasionally (which I thought was my failure to set v-hold properly), but now it seems more solid. I can't yet be fully certain that the problem's gone away, or if it's a coincidence, but I'm keeping my fingers crossed.
From the monitor's behaviour since I've owned the cab, I'm guessing that perhaps these connections were a little loose to begin with (I mentioned some occasional problems
here), and then were made worse by my lazy tating.
I am still a bit concerned about the monitor's random power-offs. When it shut off, it would make a horrible grinding sound and then cause a bit of a smell.

Is this a sign of damage?
You do not have the required permissions to view the files attached to this post.