Discharging CRT anode and capacitors on a VT52 DECscope

From: Tony Duell <ard_at_p850ug1.demon.co.uk>
Date: Fri May 28 17:39:28 2004

>
> >>>>> "Tony" == Tony Duell <ard_at_p850ug1.demon.co.uk> writes:
>
> Tony> Use a limiting resistor!
>
> But not a 100 ohm one -- that might as well be a short. A megaohm is
> probably better. Voltage rating may be an issue.

Yes. Most small resistors are only rated for 300V or so, so you need 100
of them in series, really. Try using 100 off 100k or 1M :-)...

High voltage resistors do exist (I've used some rated at 7.5kV, which
means you only need 4 of them), but you need to be careful how you mount
them.

If you do a lot of work on CRT based stuff, you should get an EHT proble.
It's really just a high-value HV resistor, either with a built-in
microammeter in series, or as part of a potential divider to use with
your DMM). It's good for discharging the CRT, and it's useful for
checking the EHT is there in the first place.

-tony
Received on Fri May 28 2004 - 17:39:28 BST