So after moving house, my PVM developed an issue where it would intermittently show the red in the picture. It took a while to figure it out as I thought it was just a loose connection but it seemed to be something internal.

The symptoms and fix

After I realised it was an internal issue, I finally could reproduce it by pushing up on the back of the casing and could introduce the issue consistently, this proved it was either a loose connection or a cracked solder joint and not a bad red beam in the CRT itself.

Once I figured that out.I had to find a way to isolate the issue, I ordered some cooking chopsticks on AliExpress so I could poke around the board while it was powered on without risking shocking myself. After reading the schematics and finding the likely area, I finally found that it was the daughter board carrying the signal that was socketed into the mainboard. I powered it off and removed it, put contact cleaner in there and put it all back together and the problem went away.

An Audio side quest

While I had it all part I figured I would address the missing audio. I did replace a few of the caps in the audio section with no success and determined it was the op-amp itself. I ordered a new one and the sound all came back in its mono glory.