BEWARE - never work on a monitor when it is turned on, or even plugged into the mains, and also be aware that they hold a charge long after they are powered off, enough to give you a nasty bite, this can also destroy multimeters.
A while ago now my trusty Commodore 1084S test monitor died before my very eyes, one minute it was displaying a borked arcade board, the next minute the CRT powered down and it started to scream, it wasn't happy.
I had bought that monitor for $10 from a bloke on trademe when I lived in NZ, its in mint condition, even has its front flap. Thought finding a replacement would be easy - not so, Commodore made about a dozen models in the 1084 line, this one was the rather damn useful DB9 shared input model, TTL and analogue RGB use the same pins on the same socket, and a little switch at the back flips between the two. The other ones seem to use 1 DIN socket for analogue and one for TTL, and they are different sockets. The last 2 years of video adaptor cables I had made for various systems were useless with any other type.
The only ones I could find were tatty ones being offered for the bargain price of $115 or were cheap but in Perth(>3000kms = shipping $$$). The guy who gives me arcade boards to fix kindly sourced me a 1084 screen but it wasn't the right type and even with an adaptor I could not get it to display the output from an arcade board, no idea why, my wiring checked out.
So I decided to have a go and fix it, I dropped $20 on the service manual and schematic for the screen. First point of call was the power supply, the manual listed what should be coming out of the PSU stage and bingo - every output line was very low voltage-wise, either the PSU was stuffed, or something upstream was taking far too much current.
Main suspect on these monitors is the line output transformer (LOPT), which are known to go short circuit with old age and it would certainly drain too much current.
Desoldered the LOPT and went looking for short circuits, found one.
25 Ohms between a primary and a secondary winding - not good, there should be no connection whatsoever.
Found a new one locally for $41.
Fitted the new one, bracing for smoke and smells I plugged it in, it needed a couple of small adjustments to the pots on the LOPT but...
Now I can put the lid back on and get back into my confort zone.