Thanks again, your help is valuable. I understand the suggestion regarding the resistors. Provided I check the value, could I use normal resistors even if they are not specific for high voltage?
Since I disassembled, cleaned, reassembled the critic resistors and set the correct 1.60 voltage on U1540 pin 4, I haven't had the problem again (but it's too early to say I've won). The previous HV setting was too high (1.65V), so maybe the inverter was a bit overstressed?
Before I do anything else, I want to take advantage of the opportunity offered to me by a friend of this group: he also lives here in Florence and has a wonderful 13302A in mint condition. Next Sunday I will go to him to read/measure his oscilloscope, which I am sure is working fine, and compare the results with mine.
I will keep you informed. Thanks again Gianni
P.S. Who is Samantha?
