23-04-2020, 11:18 AM
(This post was last modified: 23-04-2020, 11:24 AM by Mike Watterson.)
The eye is has a triode driving a "CRT" deflector electrode. The HT/ anode resistor, for a particular grid voltage, will affect the deflection. The Target pin HT has less effect, mostly brightness.
0V = no signal = anode voltage / deflector pin low, maximum shadow
-ve grid enough so anode voltage is high = no shadow. = Strong signal. I'd have thought much more negative than -2.5V.
So check that resistor on preamp anode/ deflector pin hasn't gone high, or HT isn't low.
The eye doesn't open even as much as 1/2 with no signal. It goes about 2/3rds lit, 1/3rd shadow (no signal = 0) to fully lit (preamp cut off).
A video I made:
https://www.youtube.com/watch?v=JhNvdOW2zX4
0V = no signal = anode voltage / deflector pin low, maximum shadow
-ve grid enough so anode voltage is high = no shadow. = Strong signal. I'd have thought much more negative than -2.5V.
So check that resistor on preamp anode/ deflector pin hasn't gone high, or HT isn't low.
The eye doesn't open even as much as 1/2 with no signal. It goes about 2/3rds lit, 1/3rd shadow (no signal = 0) to fully lit (preamp cut off).
A video I made:
https://www.youtube.com/watch?v=JhNvdOW2zX4
