Running CRTs without implosion protection glass

dwight dkelvey at
Sat Jul 2 09:40:19 CDT 2016

I suspect the warning about arcing was that it could damage the regulator.

The voltage would increase, increasing the Xray level.

Depending on the metal being hit by electrons, it take a minimum level

before Xray emission starts. As I recall, the regulator on a color TV

was intended to keep it below that threshold.


From: cctalk <cctalk-bounces at> on behalf of drlegendre . <drlegendre at>
Sent: Friday, July 1, 2016 6:27:27 PM
To: General Discussion: On-Topic and Off-Topic Posts
Subject: Re: Running CRTs without implosion protection glass

" I do remember
reading that the EHT rectifier diode valves and shunt stabiliser triodes in
colour TVs gave off enough Xrays to be dangerous"

This is true. I have here an old HV octal-base tube rectifier that came out
of a color set. The vacuum envelope itself is encased in a second outer
envelope, which seems to be made of something like 3/16" lead. The outer
envelope carries multiple warnings about x-ray emissions, and instructs you
to avoid arcing the anode to the case, or causing any other sort of
mechanical shock or damage as it may reduce the x-ray safety.

Of the countless thousands of tubes I've sorted, this is the only one I've
ever come across.

On Fri, Jul 1, 2016 at 3:40 PM, Toby Thain <toby at> wrote:

> On 2016-07-01 4:08 PM, Fred Cisin wrote:
>> Not a very good comparison because one is pointed at your head for
>>> months or years and the latter is momentary.
>> On Fri, 1 Jul 2016, tony duell wrote:
>> I am not convinced that the effect is purely cumulative anyway. In other
>> words,
>> a lower intensity (and lower energy) beam for longer might not do as
>> much damage as a brief pulse from a high intensity, high energy source.
> Granted. But this is all well studied, we can just look up the numbers and
> the science. Probably something people using unshielded CRTs are best
> motivated to do.
> --Toby
>> The "pro-nuclear" community calls it the "LNT" ("Linear No Threshold")
>> premise.
>> How much of the health damage of early color TV was due, not to the
>> hardware, but to the quality of the content?
>> (USA networks were/are clearly worse than BBC)

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