[andyjohnson0]

From what I understand of this, the danger comes from charge stored in large capacitors. So what is the longest that these capacitors can hold a significant charge if the crt is left disconnected from mains power? Hours/days/weeks? Is simply waiting long enough a reliable way to render a crt safe to work on?

(Irrespective of the answer to this, there is no chance at all that I would ever mess with crt circuitry. But I am curious.)

[kmbfjr]

I used to bench repair on broadcast monitors. Typically, the flyback circuits have bleeder resistors and they discharge in several seconds. But you can never trust them. They can stay charged for weeks if the capacitor is good. An old capacitor damaged by heat will still hold a charge for hours. I always shorted them before replacing.

[ComputerGuru]

I got a really nasty shock from a capacitor in a flash (as in camera) that was powered down for weeks, back in the 90s.

[qingcharles]

When I was an asshole little kid I would pull these out of disposable cameras and use them to Tase people at school.

[zxexz]

I remember building a crappy, but extremely dangerous (to the user), Gauss gun out of a stack of discarded disposable cameras, when I was much younger. I remember pulling out the capacitor and the charging circuit was pretty easy, and you just hook them all up in parallel, connect to a stack of AA or D cells in parallel. Still amazed I never died from doing crap like that. Definitely vaporized a few sections of skin and lit sections of my hair on fire a few times :)

I recall repurposing the Gauss gun as a tiny "handheld" EMP that would vaporize a section of wire. Made a Win95 thinkpad (ancient now, old then) do funny things.

[ComputerGuru]

I guess some clarification on the word "tase" is required. In my case, the shock threw me back some distance – I won't give in to hyperbole and say "threw me across the room" but 'twas nothing like the gentle tickle of 120VAC or the throb of 230VAC.

[extrapickles]

If the discharge circuit is not present/functional, it can be months[1], even if the capacitor was discharged at one point.

When working with high voltage/power equipment, its best practice to keep the capacitors shorted while you are working to keep dielectric absorption from “recharging” the capacitor to 1-15% of its rated voltage.

[1]: https://academic-accelerator.com/encyclopedia/dielectric-abs...

[throwaway2037]

    When working with high voltage/power equipment, its best practice to keep the capacitors shorted while you are working to keep dielectric absorption from “recharging” the capacitor to 1-15% of its rated voltage.

Wow, I was not aware. Nice tip. Does this also apply to TVs and computer monitors from the 1990s? Are they high enough voltage/power?