I would like to take advantage of the post for any questions @Hugo, I don't know if you know Olivetti Italia monitors, especially the monochromatic series they released with the PC128S (aca Acorn BBC clone). I have a couple of which one works and one that does a strange thing, the screen turns on but you see the wavy image at the edges, and sometimes it seems to darken and disappear completely the image, in reality I left it abandoned because the flyback was very hot, but I don't know if it was normal or not.
Then I would have two other RGB color monitors again for Olivetti PC128S but I don't know who these monitors were produced by and if they were in any case designed by ACORN or for example by third parties such as Philips or Daewoo, I haven't turned them on for at least 20 years and they too were in a humid place..
Finally, I have a Macintosh Classic, restored, it works but with a strange defect, which happened after an accidental short circuit caused by me making a diode on the power supply wrong, what happened to me, the final power mosfet exploded which in turn blew up a voltage regulator chip and an optocoupler, but consequently also two 1n4148s and a transistor on the tube board. Changed everything and it's back to working but if I keep it off for a week and then I turn it on I like the brightness at maximum and I see the retrace lines but after a few minutes it darkens and returns to normal functioning, even if a little too dark but it stabilizes. The electrolytic capacitors on the board are all new, only the original NPs, and diodes and resistors are left, what can cause this defect of the G2 which decreases as it heats up? Before this error of mine it worked normally, there must be some other component that was damaged.