I recently brought my Lisa 2/5 back out of the cupboard to have a tinker during lockdown.
Unfortunately after a few minutes the contrast goes very dark and the image starts to shrink on the right hand side.
I haven't dared to leave it on long enough for something to go bang...
The BU406 is quite hot, but probably within normal limits.
Any ideas would be much appreciated
I've attached the video board schematic for reference.