Check the blanking.
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On 4/15/2021 9:25 PM, Doug wrote:
I picked up a little Sony/Tektronix 380 Video Waveform/Vectorscope recently. It powered up but no trace,
just a faint glow on the screen. It looked to me that the X10 HV multiplier was bad so I dug out the epoxy
and made a new one. Now the glow is bright but still no trace and the brightness is not affected at all by
the intensity control or the grid bias trimmer, which leads me to believe the CRT is bad.
I have voltage on the focus grid and I tried disconnecting the H and V plates - no change
I removed the CRT to look at the insides. Nothing looks broken or out of place as far as I can tell.
The grid bias trimmer varies the heater to grid voltage from 70V to 130V with, as I said, no intensity change.
Heater is at -1950V.
Looks to me like the CRT is bad. Am I missing anything? Any suggestions?
I've posted some photos under "380".