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Re: X-rays from light bulbs/Tesla Coils

Very interesting.. There was a discussion a while back on this list where
someone was going to try and use picture tubes as the primary cap in a TC. 


This is really interesting.. So what is the mechanism that makes CRT's
generate xrays?  With the normal anode voltages I wouldn't think you'd get
much if any (of course, now that I think about it, if that same voltage
made xrays in the HV rectifier, it would make it in the CRT).  Is it one of
these ion bombardment things, like the cold cathode xray tubes that have
been mentioned?  The tubes that fail the test: what sort of characteristics
do they have? Is the test condition at a much higher 2nd anode voltage than
rated?  Most of the TV's I have taken apart recently have a spark gap to
limit the 2nd anode voltage.

I don't know that I'd use a CRT as a cap: big, bulky, and not very much C
per volume or pound.  But, they are cheap (free)..

Of course, if you zap the CRT with the secondary voltage at several hundred
kV from the TC, you have a good chance of making xrays.

----------
> From: Tesla List <tesla-at-pupman-dot-com>
> To: tesla-at-pupman-dot-com
> Subject: Re: X-rays from light bulbs/Tesla Coils
> Date: Tuesday, September 14, 1999 10:48 AM
> 
> Original Poster: "Mad Mike" <mglass-at-netusa1-dot-net> 
> 
> Jim
> I never said the x-ray hazard was from the picture tube in the old sets.
> Picture tubes were and are engineered so they won't be an x-ray hazard
under
> NORMAL operating conditions as I stated. I believe the technology in CRT
> design and materials have progressed a bit since the 40s and 50s and old
> picture tubes would be better canidates if one wanted to try to get
x-rays
> out of one . I know the government standards are more strict on modern
ones.
> (regulations never get less strict). Yes, you had a much greater x-ray
> hazard from the rectifier tube, I don't disagree.  X-rays are produced in
> the CRT itself if it is improperly manufactured or if the hi-voltage on
the
> anode is excessive, and the CRTs from the 40s and early 50s were worse.
The
> CRT manufacturing industry of which I am a small part is required to test
> CRTs for X-rays, the standards are higher now. (or is it just another
stupid
> government regulation and there really is no potential hazard at all?)
TVs
> don't have rectifier tubes anymore, but we are still required to test the
> CRT periodically, WHY?  We have had CRTs fail for excessive x-radiation
in
> house within the recent past because of some bad glass so I know they are
> capable of producing x-rays. I've worked in the CRT manufacturing
business
> for 26 years, I may not be a design engineer or a Phd. but I do know
> something about picture tubes and how they were and are manufactured and
> tested. The original poster wanted to know IF a crt  COULD be made to
> produce X-rays, not, if a TV or computer monitor as a unit operating
under
> normal conditions makes x-rays or if other circuits in the set would
produce
> x-rays. The answer was and still is, YES, a CRT can under the right
> conditions, I stated one of those potential conditions, and the old black
> and white CRTs from the 40s and early 50s which contain no shadow mask,
> different glass, different phospher material, inferior outdated designs 
and
> sloppier manufacturing techniques WILL be better than modern day color
> displays for producing x-rays under the ABNORMAL conditions I stated
> earlier, but they will not under NORMAL operating conditions be any worse
> than a modern tube (which produces next to none). Now,  wether or not
either
> could be made to produce strong enough x-rays to make a GOOD radiograph I
> don't know or care, but a CRT can definitly be made to produce x-rays. .
> Mike KB9NZQ
> ----- Original Message ----- From: Tesla List <tesla-at-pupman-dot-com>
> To: <tesla-at-pupman-dot-com>
> Sent: Saturday, September 11, 1999 4:20 PM
> Subject: Re: X-rays from light bulbs/Tesla Coils
> 
> 
> > Original Poster: "Jim Lux" <jimlux-at-jpl.nasa.gov>
> >
> > And, the xray hazard from old color TV's wasn't from the picture tube,
but
> > was from the HV rectifier in the 2nd Anode power supply.  These tubes
are
> > available in two forms (with the same part number, of course) one with
a
> > lead glass envelope, the other not. Apparently, they are
distinguishable
> by
> > their weight.  I seem to recall an article in "the Bell Jar"
> > (http://www.tiac-dot-net/users/shansen/belljar/ ) talked about it, and had
> some
> > radiographs.
> >
> > ----------
> 
> 
>