Adjusting pots on tube of monitor while switched on

Ouch! That hurts.. I got zapped from the neckboard on my ms pacman cocktail table while reaching around inside with it on.. That was a mistake that I don't plan to repeat any time soon.. ;-)

- Mike

My grandfather's Christmas party piece was to open up the tin box that housed the EHT rectifier, and with a damp wooden handle screwdriver, draw an arc from the anode terminal.

--
Mark
Please replace invalid and invalid with gmx and net to reply.

I remember one of those translucent orange handled screwdrivers would do quite well too. I've no idea what the resistance of the handle would be, but I'd trust it to be a bit more consistent than a wooden spoon.

Slightly safer now of course, though not quite so much fun, because voltage triplers are the usual thing - not such a big spark.

Rod.

My father had an eht voltmeter that consisted of a calibrated spark gap. You turned a knob bringing the balls closer together until the spark jumped the gap. Then you read off the voltage on a scale.

--
Ashley
For Windsor weather see www.snglinks.com/wx/

How accurate would this have been ?

Wouldn't humidity / air quality have a measurable an effect on a spark gap ?

//Clive.

We used to do that to test for EHT, firm we worked for in those days was too bl**dy tight to buy one.

Had the odd belt of many a CRT that wasn't discharged, but by far and away were aerial isolator plates that had been bypassed and that wasn't much fun if you we working up on a roof.

Metal ladder, damp soil, live aerial..Nasty!.....

>

--
Tony Sayer

Were they not sealed devices ?

The anode terminal of the HV rectifier tube was connected to the flyback which was 15.7 kHz AC - similar to the output from a small Tesla coil. So, as long as the screwdriver had some capacitance, the conductivity of the handle probably didn't matter much.

With modern flybacks, the output is DC filtered by the CRT capacitance, so the effects are quite different.

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I was referring to the fact that most modern EHT circuits will only have 8kV pulses instead of 25kV pulses, because they use a diode/capacitor multiplier and a lower voltage transformer.

That happens anyway doesn't it? The coatings on the inside and outside of the bowl of the CRT constitute the EHT smoothing capacitor.

Rod.

voltage

and

What I was trying to say is that in a modern CRT TV or monitor, there is no place to find the full HV pulses - 5 kV or 25 kV - since the only output of the flyback goes directly to the CRT anode and its capacitance.

In old once, the flyback output went to the 1B3 (or whatever) anode and was AC at that point.

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the

If you mean the multiplier, then yes, it would incorporate the EHT rectifier which would otherwise have been a separate diode. The output terminal of the multilplier unit would be the cathode of the diode, so no AC at that point.

Yes, a whacking great pulse equal to the full EHT potential onto the anode of a separate diode. Treat with extreme respect!

Rod.

Phew!

Hmmm. Let me have a look and see if I can move .... :-)

i thought that some posts to a very recent thread said that HT was not actually so very dangerous but would throw you across a room (the main danger being how you landed).

Everyone loves to diddle with those magnet rings.... :)

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Electricity doesn't "throw you across a room", so if somebody's description included this statement you know how much you can trust the rest of it.

If you find yourself somewhere else in the room after an electric shock, it will have been your own muscles that put you there.

Rod.

Steady on Roderick! Now that's a wee bit pedantic. Are you not happy with ellipsis? Otherwise we will have to sort out things like:

Water does not satisfiy your thirst, it satisfies your body's thirst.

A car does not run on pertrol, a car's engine runs on petrol.

You do not watch television, you watch images on the tube of the television.

PHEW! :-0

Alex Coleman spake thus:

Thank you for de-pedantifying that.

--
Pierre, mon ami. Jetez encore un Scientologiste
dans le baquet d'acide.

- from a posting in alt.religion.scientology titled
"France recommends dissolving Scientologists"

No, the images and sound are usually a waste of time. Watching the electronics is more educational. :)

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Apologies if I underestimated you, but there are plenty of people who apparently really believe that an electric shock will "throw you across the room". I've no idea how they think it does this, and probably neither have they, but they've heard it somewhere so it must be true and will tenaciously defend this viewpoint against all attempts to correct it.

Rod.