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How dangerous or lethal is HV in CRT devices?
james_s:
I've been zapped by the EHT on a 19" CRT before, it HURT, but I'm still here. It felt like a powerful static electricity zap. Technically it could mess up your heart, but it's unlikely in most cases. Even so, be very careful.
The ~180V B+ in many CRT displays is actually much more dangerous than the EHT, it can deliver a great deal more current.
andy2000:
By far the most dangerous part of any CRT display is the mains supply and B+ voltage. The HV supply is well insulated, and not capable of supplying much current. A microwave oven is much more dangerous.
Ian.M:
... except as I stated above - mains derived EHT for a CRT in a really vintage CRO or valve TV is generally at least as dangerous and possibly more dangerous* than the HT in a microwave.
* Its typically several times the voltage of microwave HV so will jump further to bite you! OTOH the reservoir capacitor is typically a much lower value than a microwave one, so there *may* be less energy instantaneously available to blow chunks out of your fingers and stop your heart! :-\
jonpaul:
Bonjour a tous: Just notice this thread now, late to respond...For decades I had designed and manufactured special purpose magnetics, HV modules, CRT display drivers and HVPS.
1/ classes of HV, with different hazards:
Mains freq transformer raw PS with large filter caps
High freq (flyback) transformer with voltage mult or rect, small caps (most CRT)
DC HV at the CRT leads
2/ Shock damage is often collateral: Your hand touched the CRT Ultor anode connection, hand and arm are shocked, your sudden motion throws you to the floor or hand hits the CRT (see below)
Certainty shock effect its unpredictable as some are more susceptible (moist skin? Pacemaker?, Elderly? Standing with thick rubber shoes or barefoot on concrete that's wet?)).
3/ CRTs are large vacuum vessels designed to be in a TV or scope with safety shields and safety bezel.
In servicing we may have to defeat interlocks and remove such shields.
Striking a CRT can break the glass, causing a serious implosion.
Glass shards are thrown many meters as shrapnel.
Extreme danger to face, eyes, bleeding...VERY bad.
Risk of implosion damage is like the CRT dia exp 3. (volume enclosed)
(NOTE: in my experience I have had all sorts of shocks and at least two implosions of CRT or arc lamp)
4/ DC and mains freq is most dangerous, high frequency AC HV like a flyback or Tesla coil may no shock, but the RF energy may cause burns and arcs.
5/ Typical scope HV 2kV...15kV, color TV were up to 25 kV and projection TV to 35kV.
The Aquadag (conductive anode coating) to ground capacitance is typically between 50...3000 pF.
Calculate stored energy 1/2 C *Vexp2.
I strongly suggest the OP read the literature and books of CRT and HV safety before proceeding with his experiments.
Nikola Tesla (NOT THE CAR!) would always stand on rubber mats and keep one hand in his pocket!
Bon Chance!
Jon
Labrat101:
This is a very interesting that this has come up . How dangerous or lethal is HV in CRT.
Reminds me of an accident that happened in one my father's TV & Radio shops .. Way back in the 60s.
One of the techs was working on a very large TV . When he some how touched the HV wire to the tube . These old
sets had about 25 - 30KV . The The shock through him across the room with enough force to Crack his head open on the
Wall on the opposite side of the work shop . If I remember right, he had over 10 stitches.
Its not so much the voltage its more how your body mussels react to electricity .
And whats in your flight path when landing.
Golden Rule Discharge First . :-+
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