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From: paul@dual.UUCP (Baker)
Newsgroups: net.consumers
Subject: Re: are ion generators bad for machinery and other living things?
Message-ID: <1027@dual.UUCP>
Date: Mon, 3-Jun-85 16:26:19 EDT
Article-I.D.: dual.1027
Posted: Mon Jun  3 16:26:19 1985
Date-Received: Thu, 6-Jun-85 02:29:06 EDT
References: <4147@allegra.UUCP> <2221@sun.uucp> <2211@ncrcae.UUCP>
Organization: Dual Systems, Berkeley, CA
Lines: 17

> As a EE with quite a bit of experience with CRT design, I have *never* seen
> the cathode put at a high negative potential while the anode is grounded.
> I think if you check, your SUN and other CRTs run a second anode potential
> at around 12kv to 20kv, with the cathode grounded (or near ground ).  This
> makes the circuit design in driving the grids or cathode with video
> information much easier.  Remember, there is about a quarter inch of glass
> between the phosphor an the front of the tube which is enough to prevent
> a shock hazard.

Many old Oscilloscopes were designed with the cathode at a negative
potential.  These were typical vacuum tube designs.  The anode was
connected to about 200 Volts, the supply for the rest of the
circuitry.  The deflection plates were connected to differential
drivers.  The cathode was connected to about -1kV.  I made one of these
in the dim and distant past.  There is also a similar design in 1966
RCA receiving tube manual.  I have, however, never seen a T.V. type
display designed this way.