Update.
I swapped the transistor and checked things around.
The monitor powered up and stayed in standby happily (Yay!). When I applied VGA signal, the monitor fully powered up, I had HV, a weird image on screen and then The Magic Smoke!
The same transistor shorted (Base with Collector) and a resistor connected to it went on fire.
I've looked around and here are my notes:
- The transistor seems to be generating +70V for the neckboard. On the Neckboard there is a CVA2422TL CRT driver. I've noticed that I've got 90Ohm between GND and the 70V line on the neckboard - my other neckboard reads some Kiloohms and climbing.
CVA2422TL datasheet:
https://pdf1.alldatasheet.com/datash...CVA2422TL.html
Shall I move my attention to the neckboard? Could it be the reason why the 70V rail fails every time?
Could a bad CRT cause this issue on the neckboard? Please note I read 90 Ohm with the neckboard disconnected from everything (but the Flyback)
I don't want to give up know. The area which went up in smoke seems pretty simple - I'm sure some of you can recognise the topology, I suspect it's some voltage regulation?
When the screen came up it was pretty weird, white with blotches. Maybe someone can recognise the symptom of something? See video below.
Also, I cannot assume that the trimmers around the PCBs haven't been touched. Still, I wouldn't expect components to go up in flame if something is misadjusted?
Here is the video of the accident (I have a small youtube channel where I publish my repairs):
https://www.youtube.com/watch?v=YqpgZc0HX2M
Attached some pictures - the main PCB is single layer so the circuit can be easily followed there!
Thanks so far!