[cctalk] VT100 Monitor Board

Hello, As some may recall I have been working on getting a VT100 going again. I have made good progress and I think the main board is probably OK now (see here if you are interested: https://robs-old-computers.com/2023/11/19/vt100-keyboard-constant-clicking-f ault/). Possibly I still need to replace the NVRAM, but I am leaving that until I fix the problem I want to describe next. The problem is that there is no image on the screen. This is because the monitor board is not doing anything, there is no glow from the neck of the tube etc. I have found that this is because the fuse on the 12V input to the monitor board is open circuit. Of course the worry is, why? There could be a fault on the board. I have tested the transistors in circuit with a multimeter and they appear to be OK. I used a bench PSU to give the board 12V and it drew no current (with all connectors disconnected). I tried again with the round connector attached to the end of the tube and it drew about 100mA and there was a faint glow from the neck of the tube. I am hesitant just to replace the fuse and try it. I am hoping for some suggestions on how to test this safely (in particular without involving the flyback transformer) to find if there is a fault. For information, the monitor is an Elston and I pre-emptively replaced all the electrolytics on the monitor board apart from the non-polar one. Some details of what I did are here https://robs-old-computers.com/2023/10/01/vt100-ram-fault/. Although I have since realised that I didn't replace two of them because they looked like diodes. I don't think the board I have is the one in the available printsets. Thanks Rob