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How dangerous or lethal is HV in CRT devices?

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MathWizard:
I guess there have been lots of linesmen, utility workers, industrial workers that get hurt or killed working on high energy systems. What about repair technicians back when all TV's and things had CRT's in them ? How dangerous was it really and how much worse is it if the TV was on when u made a mistake or had an accident ?

I have a couple of old things with CRT's in them, they "only" have about 1000V or so tho. I plan to know those circuits backwards before I go looking at that stuff. I wish I had an old, all/mostly discrete TV to play with.

bob91343:
As I remember it, those CRT anode potentials were indeed dangerous.  For color TV they were up in the 25 kV range.  It doesn't take much capacitance to store a lot of energy at those potentials.  And energy is what can get you.  Any voltage above around 100V will cause conduction of human tissue, enough to cause problems.  As for electrocution, I believe the old electric chairs were around just a few kV.

bdunham7:

--- Quote from: MathWizard on January 28, 2022, 04:16:28 am ---I guess there have been lots of linesmen, utility workers, industrial workers that get hurt or killed working on high energy systems. What about repair technicians back when all TV's and things had CRT's in them ? How dangerous was it really and how much worse is it if the TV was on when u made a mistake or had an accident ?

I have a couple of old things with CRT's in them, they "only" have about 1000V or so tho. I plan to know those circuits backwards before I go looking at that stuff. I wish I had an old, all/mostly discrete TV to play with.

--- End quote ---

A CRT television shock certainly could stop your heart if you were unlucky--and it did happen--but the majority of the time you just got a really hard wallop, like a very powerful electric fence.  The total energy in an CRO without post-deflection acceleration is reasonably low, but not something I would willingly risk getting fried by.  I don't know how much worse it would be if the device were on, but it certainly isn't better.  With a capacitor, even if you can't let go it will finish discharging very quickly. 

AntiProtonBoy:
EHT output from flyback transformers are typically around 25 kV and deliver very little current on their own, if disconnected from the tube. I re-purposed a few of those, using a custom driver circuit, and got zapped by those a countless times. The real danger comes from the tube itself, as conceptually operates like a high voltage capacitor, and an unplanned anode discharge through your body could be potentially lethal.

eti:
A teenager like me, back in 1991, seems to have survived well, since I was trained well and didn’t make daft assumptions.

Back in ye olden days, back when people had brains that were generally fully functional, and I’d think that generally no mollycoddled and dumbed down fools were in charge of repairing equipment, when training manuals and service schematics were properly written, engineers were fully competent and aware of the high voltages present on the usual suspects. This fact has been pointed out by Paul Carlson (“Mr Carlson’s Lab” on YT) many a time - people didn’t need “protecting” with PVC boots and isolated guards, as they knew what they were doing.

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