Discharging a CRT - easily!

[Down Under]

Originally Posted by lnx64

So I'm not discharging the CRT safely. I'll need a bleeder resistor screwdriver.

I agree with old_coot88, no probs with the way you're doing it, but this way seems to prevent recovery and the paper clip is nice n' easy to slip under the anode cap.

[Geoff Bourquin]

Does anyone know what kind of current goes through the screwdriver when a fully charged CRT discharges? Using my HV meter only draws around 40uA, because the meter impedence is about 800 megohm. Can the tube be damaged by the spike of current from a direct short? I doubt it can, but I don't know so I have to ask.

[Tubejunke]

My college professor once warned me in the middle of a lecture to "never; under any circumstances" use a screwdriver to discharge stored current. I later told him about all of the television repair literature that I had read in my life which stated to use a screwdriver, but he stuck with his guns and said to always use a resistor and that a screwdriver was a safety hazard. I still use a screwdriver; I just never use an old one with a wooden handle like I did once when I was a kid! ZZZAPP!!

[old_tv_nut]

TVs are designed to take the occasional CRT arc without killing anything, so the energy in one discharge is not going to destroy anything unless it's a bad design. There is usually a series resistor in the cathode circuit to limit arc current. The professor's rule not to use a screwdriver is a good general one and definitley applies to items with an unknown and possible large amount of stored energy; so, if you didn't *know* discharging a CRT with one is safe, it would be better to use a resistor.

[old_coot88]

The Prof's sage advice is probably more applicable to charged electrolytic caps than pic tubes.

[Electronic M]

I'm a screwdriver and alligator jumper guy....And after about a half-dozen bad recovery zaps from my first roundy(I was beginning to think the thing was possessed), and after getting real mad I formulated my current SOP of leaving the alligator clip lead on indefinitly(I defy any CRT to recover while that lead is on).

[Winky Dink]

I guess this would be a good time to ask what I should be doing with an electrostatic CRT. Having no Aquadag on the outside, and no accessible HV line, does it need to be discharged?
- Winky

[Electronic M]

I've never tried on my Moto VT-71....I just unplug the tube and avoid touching the pins(doubt they hold a charge but I don't want to learn the hard way LOL).