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#1
02-11-2011, 07:29 PM
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Safe way to release CRT vacuum?
A visitor to my website asked what is the safest way to release a CRT's vacuum seal. He is making some kind of art installation. Never fear, he's using new-ish BPC discards, nothing vintage.
Never having done this myself, I did a thought experiment. Seems you could use a mini torch or soldering gun to unsolder the pins and remove the base, and then twist that little glass nib at the end with a heavy plier (wearing stout gloves and other protective gear, of course). Better ideas? Before you suggest any cowboy stuff, picture me being sued by the estate of some starving artist who caught a shard of glass in the jugular and was found with a printout of my email instructions in his cold, dead hand  Phil Nelson 
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#3
02-11-2011, 07:53 PM
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Leaking a CRT
Phil,
If he doesn't want a perfect looking screen, then just gently hit the very tip of the base with a small hammer, or large pliers. The air will slowly leak out, making it safe to handle--but it goes to air too fast to save the looks of the face. If you hit the neck first, it can really explode (implode-then-explode)...but once you're clipped the tip to take care of the vacuum, you can then knock off the neck easily. I've used this method when a tube tests bad and must be replaced, but is stuck by tar or whatever, and I'm afraid of yanking it out and eating glass! Harry
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#4
02-11-2011, 07:55 PM
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I've whacked the neck with a hammer many times and never had a problem, they were tubes that were installed in the cabinet for the most part.
On the last tubes I had to dispose of, several shot 7JP4's, where whacking the neck isn't an option, I drilled a small hole through the Bakelite base and just kept going with the drill on low speed until I broke the nib. Some folks punch a hole in the metal anode connector but that makes me nervous, banging on the bell of the tube in any amount is scary. If you have a really sharp punch you can gently work the punch through the thin metal anode and release it that way. A modern CRT should be very easy to break the nib off the base since it fairly exposed. If it were a Fishtanker converting a vintage set the method I would recommend would be to clutch the tube tightly to their chest and jump off a tall building Last edited by Eric H; 02-11-2011 at 07:59 PM.
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#5
02-11-2011, 08:03 PM
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I assume that he wants the CRT to look "normal" after it is let up to air... knocking/twisting/torching off the tip seal may allow enough inrush of air to blow off some of the phosphor. In cases like this, I wrap the tube in a heavy blanket, leaving the HV button exposed, and pound a sharp scribe point through the HV button. The tapered scribe can be pulled out slowly to control the inrush of air. I have done this many times and never had a problem. (don't miss and hit the tube
 )jr
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#6
02-11-2011, 09:55 PM
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I was once given a rather large (27" or larger) new crt that was NOS but with a bad scratch on the face. It proved no good to me, except that inside were the official instructions from RCA for how to kill the vacuum in the dud-the old ice pick in the anode button method. I have used this ever since, with no problems. It takes only a few very gentle taps.
__________________
Bryan
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#7
02-11-2011, 10:39 PM
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Quote:
__________________
Brian USN RET 22YRS (Avionics/Cal) CET-Consumer Repair and Avionics ('88) "Capacitor Cosmetologist since '79" When fuses go to work, they quit!
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#8
02-11-2011, 11:29 PM
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Ive used a small drill on the anode button...
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#10
02-12-2011, 11:48 AM
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Quote:
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#11
02-12-2011, 11:50 AM
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Thanks, I passed the advice along to the art guy -- along with dire warnings to don all of his Star Wars protective gear.
Phil Nelson
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#12
02-12-2011, 12:00 PM
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Quote:
Especially on a large B&W tube... I have always whacked the neck, and done so with glasses on and my chin tucked in my chest (no neck exposure) in case of a fluke accident. Charles
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Collecting & restoring TVs in Los Angeles since age 10
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#13
02-12-2011, 01:22 PM
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My brother and I used to throw half a brick and duck around... Oh, you said "safe". Never mind.
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Chris Quote from another forum: "(Antique TV collecting) always seemed to me to be a fringe hobby that only weirdos did."
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#14
02-12-2011, 02:17 PM
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I take the electronics off the back and break the little nibbin off the end.
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#15
02-15-2011, 09:10 AM
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You can do like Scott of the now defunct Hawkeye CRT rebuilding factory: wrap a
few layers of duct tape around the neck of the tube, and use a very sharp steel bit rotating at high speed to drill the glass through the tape. The way Scott used to do it, it seems like it would heat the glass rather than really drill it, and eventually a small hole would result, letting the air into the tube over a few hours.
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