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Old 07-30-2017, 11:21 PM
CPQ5360 CPQ5360 is offline
Trent
 
Join Date: Jan 2013
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Can CRTs hold a charge after they've been vented?

I feel like this is a dumb question, but I can't for the life of me find the answer by googling. I've got a bad 5" tube that I'd like to vent and keep as an ornament.
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Old 07-31-2017, 12:25 AM
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old_tv_nut old_tv_nut is offline
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The charge is held between the inner dag and outer dag acting as capacitor plates and the glass acting as the dielectric. Venting makes no difference, except that the charge might leak off faster due to humidity in the air.

Just discharge the tube properly before you vent it, and there won't be any charge to worry about.

REMEMBER that discharging once is not enough, because the glass dielectric can undergo electrical relaxation and restore part of the charge. To be safe, discharge once, wait 30 minutes or so and discharge again. On the other hand, relaxation is worse if the initial voltage is higher, so a 5 inch tube, which will use lower voltage, and have less total charge, is not going to have anywhere near the secondary charge that a large color CRT would have.

Edit: If the tube has been sitting around unused for months, it probably has no charge anymore, which you can verify when you get no spark on the first discharge.
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Old 07-31-2017, 10:13 AM
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Jon A. Jon A. is offline
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I accidentally zapped myself twice with CRTs that had been on recently, one of them vented. It'll get your attention but it's no big deal. I'm sure I got an even bigger hit from accidentally touching the case of the horizontal output transistor in my daily watcher while it was running. Again, no big deal. You're likely to get worse from touching a doorknob during cool, dry weather.
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Old 08-01-2017, 01:21 AM
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Boobtubeman Boobtubeman is offline
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I got a bite from a necked color tv once while pulling the remains of the gun out of the crt... The struggle is real..

SR
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