View Full Version : CRT "disarming"


Jon A.
01-18-2014, 08:14 PM
Getting rid of some sets that are too new for my collection, and for the collections of most others. Anyway, I read that a CRT can build up a charge again after being discharged. That being said, can a CRT in which the vacuum has been let out (I've done this to two of them so far) hold a charge at all? Also, do the pins at the neck carry enough of a charge to deliver a shock with the CRT in working order? Finally, it's the CRT that holds the charge and not the flyback, right?

bandersen
01-18-2014, 09:19 PM
Sure, a CRT with no vacuum can hold a charge. It;s the conductive surfaces and glass that form a capacitor that holds a charge. No, the base pins don't hold a charge. The flyback doesn't hold a charge, but there's often a "doorknob" HV capacitor connected to the HV rectifier output that can.

zeno
01-19-2014, 07:57 AM
I think all your sets are solid state. Most will bleed off
quickly & have little or no charge.
Sometimes after discharging one it will come back a little.
Besides the anode the only place you may have a charge is the
anode lead. So do it like this.....
Discharge set several times over a few minutes.
Attach anode lead to chassis ground like the tuner or IF shield.
Before moving discharge again. Carry with anode away from you.
Only carry by the screen never by the neck.
If you do get nailed the danger is dropping the tube not
the shock.

73 Zeno:smoke:

Jon A.
01-19-2014, 08:03 PM
Yup, all solid state, and rest assured I wouldn't be junking any sets that are old enough to use tubes unless I had one that is a total basket case. Do any SS sets have this "doorknob" HV capacitor?

TVTim
01-19-2014, 09:01 PM
I think all your sets are solid state. Most will bleed off
quickly & have little or no charge.
Sometimes after discharging one it will come back a little.
Besides the anode the only place you may have a charge is the
anode lead. So do it like this.....
Discharge set several times over a few minutes.
Attach anode lead to chassis ground like the tuner or IF shield.
Before moving discharge again. Carry with anode away from you.
Only carry by the screen never by the neck.
If you do get nailed the danger is dropping the tube not
the shock.

73 Zeno:smoke:

Sage advise.

zeno
01-20-2014, 07:26 AM
Yup, all solid state, and rest assured I wouldn't be junking any sets that are old enough to use tubes unless I had one that is a total basket case. Do any SS sets have this "doorknob" HV capacitor?
None. They were used in the early B&W days. Now part of
history along with the ion trap & channel 1

73 Zeno:smoke:

Jon A.
01-22-2014, 06:42 PM
Much easier to pack up and dispose of now. I'll probably be considered crazy for having done this, but whatever. The metal had already been discarded by the time the second photo was taken.