Measuring HV in an electrostatic set, tips?
 

I’m a little new to electrostatic TVs and I have a Hallicrafters T54 and I want to measure for HV on the 1B3 inside the HV cage, however when I put the tube extender in and put the 1B3 in the extender, in order to test, the plate cap is too short and won’t reach the terminal on the tube.

Any recommendations? I will be using a pomona hv probe.

Also, should I be hearing a high frequency horizontal oscillator sound or a motorboating vertical sound on a working electrostatic set?

The filtered HV leaves the cage on the thickest wire and is easily accessible on the HV terminal strip under chassis below the cage. There's a HV wax cap under the socket board that should be changed and usually a resistor in series with the HV wire leading out of the cage that should be checked while you're in there.

The HV is independent of the sweep circuits so if the HV is working you could have a raster, horizontal or vertical line (one of the sweep circuits not running) or even a dot (no sweep working).
Some sets you can hear vertical and or horizontal some you can't. Electrostatic sets tend to be quieter than electromagnetic sets unless something is not working properly.