WHY are electrostatic tubes wired so WEIRD?

[rca2000]

Looking at the diagram of my 48-700, 50-701 and other Electrostatic-Deflect. type sets...It seems to ME...that the CRT in ALL of them is set up in a STRANGE way..

There does NOT appear to be a "2nd anode", at least in the way we are used to in most other tubes. like a 12LP4, 21AXP22, and about any M-D tube I have ever seen. . And WHY...does the HV seem to go to the CATHODE of the CRT--I am used to VIDEO being there--and at the most 250 volts or so. On E-D tubes...the HV, through some resistors seems to end up there!!

WHY...is this????

[N2IXK]

They do it to place the deflection plates closer to ground potential, to simplify the deflection amplifier design. They apply a NEGATIVE high voltage to the cathode end of the gun, which is effectively the same as a high POSITIVE voltage at the anode end of the gun.

[old_tv_nut]

This is (was?) a common arrangement for oscilloscopes.

[miniman82]

Easier electrically to lower the cathode than it is to raise all the deflection plates.

[old_coot88]

Originally Posted by miniman82

Easier electrically to lower the cathode than it is to raise all the deflection plates.

Yet in other topologies like the Motorola VT-73, they do raise all the deflection plates with positive HV while keeping the cathode end of the jug 'conventional'.
http://www.earlytelevision.org/pdf/M...Sams-71-12.pdf

[miniman82]

In scopes it was advantageous to have the high sensitivity deflection plates at or near ground, I suspect to avoid noise. TV's it's not an issue, those tubes probably aren't near as sensitive.

[jr_tech]

Plus it would be undesirable to have the usual hv decoupling caps in series with the deflection plates if decent low frequency (or dc) response is desired.

jr