I knew it but never knew why.

The same thing applies for most electronics.
The time required to discharge the capacitors varies depending on the device (i.e. how much capacitance the device has).

Various devices can hold dangerous amounts of charge for a very long time (days or more):

• The old CRTs (the actual tube!)
• Power Supplies

You need to exercise caution when working on such devices and the best bet is to forcibly discharge them using a load.
Don't just short them out with a screwdriver.

If you don't know what you are doing, you should heed the warning labels.

I'd like to hear how you clear a CRT, from zapping you dead, reason being, I may have a future need, thanks for the info heads up.

Faladu said:

I'd like to hear how you clear a CRT, from zapping you dead, reason being, I may have a future need, thanks for the info heads up.

oneskrewluse's link (Discharging Filter Capacitors) provides some options, however I would use a much heavier duty resistor than 2 W, for discharging a CRT.

When I worked as an electronic technician, we had access to giant wire-wound variable resistors.
Something like that would be ideal.

The other big thing is the "Right Hand Rule".
Always use your right hand, when you are "poking" around electronic devices.

This can reduce the likelihood of electric current passing through your heart.
If your left foot/hand is the only path to ground, you'll still be in trouble though.

Figures, I am left handed poker....
Thanks for the follow up.

My follow up is, if just sliding out a CRT, at what point is the ZAP expected to be incoming? or what is touched that delivers it?

I have a bartop touchscreen game, to even get the CRT out for a replacement will be a major under taking and have never done it, plus I have an old Vectrex, still works, but at 31 years old, it can't be that long for this world, although rarely have it on, might have to go in there and rig it up to something else, I will not claim to be an electrician at all.

Faladu said:

I'd like to hear how you clear a CRT, from zapping you dead, reason being, I may have a future need, thanks for the info heads up.

Water bath. Will have to be dried throughly afterwards (2 big fans, left overnight), and you need to check that there aren't water-sensitive components first, but that's how I inspect PSUs.

Other general advice is wearing rubber boots and use a single arm (and doing this with a friend). This will prevent the current from going through your arms or discharge through your feet (passing through the heart in the process), and the friend will be there to rescue you in case of electrocution (knowing Basic Life Support procedures would be optimal for both, any first aid manual has them, if you saw at least one episode of Baywatch you should know them as well). They call it "the buddy system". Never do something dangerous alone. Remember the movies.
If you get a discharge with this setup it will be painful and you may lose sensitivity/movement of the finger/hand for a few minutes. Better than dying anyway.

I don't use rubber gloves as I drop enough stuff already, with gloves I'm less precise than a 90-year old with parkinson.

Btw, this comment in the article is priceless:

donks Guest
July 20, 2013 6:18 pm

Alternatively, if you can't wait 10 seconds just lick the capacitor to immediately discharge it into your tongue.

I have used the 10-second trick on my MODEM as well many many times. I have learned the trick but never actually understood why. I just assumed that 10 seconds was just the right time for the unexplainable stuff inside there gets reset and that would hopefully correct the error once the power is put back on.

Now we know.