Help to repair oscilloscope Philips PM3207 (Algemeen)

door Onno-I , 05-11-2020, 19:23 (1480 dagen geleden) @ edison

Interesting. The transistor and transformer do oscillate when the base is not too positive.
What is the frequency you used? The oscillator should operate at 30 kHz

The signal you use seems to switch the oscillator on and off. But it is oscillating when it should be off, and is drawing lots of current when it should oscillate.

Please disconnect T801 from R808. feed a 30kHz sine of 1Veff into R808 and look at the signals on T801 (not the HV winding).
Touch the connection of T801 to C804 with a small, well-insulated screwdriver, 750V AC should be here, you should see a small spark if you have the screwdriver 1 mm from the connection.