Indeed some faults are frustrating to find.
Just now, I'm fighting (I will, when I have proper time) with a issue with vertical of my Telefunken delta-gun TV. Very irritating, since this occurs only sometimes, and is heat related: this not occurs when TV is cold, and most times not occurs when is hot. Most time only occurs with thermal transition (when warming)
so I donb't have much time window to play with
Then, I need some clear time to try to find the culprit, but
certainly has a culprit. I need to study well the schematic, for not shotgunning every related part, but the bhegges idea sounds very good now...
Is curious that this defect ocurred 6 months ago, vanished, and returned now, go figure...