RE: RF Shielding for CRTs

["Huesgen, Jim" <HuesgenJ@health.missouri.edu>]

Ok, I have to jump in here.  The radiation produced in old vacuum tube TV
sets did _not_ come from the CRT.  It came from the high voltage rectifier
tube which consisted of an electron beam and a target, just like a small
x-ray tube.  The black and white sets generally operated at a low enough
voltage that little radiation escaped the tube package, but with the advent
of color TV, the HVR operated at around 20 KV.  The anode of the tube was
dish shaped to partially self shield the produced x-ray beam but as the
tubes aged, the beam would drift off center with some of it striking the
edges of the anode and producing a wider x-ray beam.  Most manufacturers
placed the HVR in shielding of one kind or another but this caused the tubes
life to shorten due to heat retention.  Many service technicians would
removed the shielding during tube replacement and neglect to replace thus
creating a low energy x-ray source within the TV set.

huesgenj@health.missouri.edu


-----Original Message-----
From: BobCherry@aol.com [mailto:BobCherry@aol.com]
Sent: Tuesday, February 15, 2000 10:05
To: Multiple recipients of list
Subject: Re: RF Shielding for CRTs


In a message dated 15-Feb-2000 8:39:33 AM Eastern Standard Time, 
Tad.M.Blanchard.1@gsfc.nasa.gov writes:

> Most of the newer CRTs do not radiate hazardous RF levels.

None of the older ones did either.
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