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  #1  
Old 02-10-2017, 10:08 PM
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B&K 465 acting strange

I really love my trusty B&K 465, but when I went to use it tonight on a tube, I noticed that when I set the switch to emmision, whichever color I set the tester to, glowed blue inside the tube. I made sure I had the voltages set to the book. 40 volts on G1, about 275 on G2. I could also feel a very slight AC voltage on the tester itself at all times. What's going on with my beloved 465?
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Old 02-10-2017, 10:11 PM
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It's not the tester, looks like you have a gassy CRT.
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Old 02-10-2017, 10:17 PM
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Both RCA Hi Lite tubes that I tried did that. Are they both junk? They both looked fine before I took them out of sets.
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Old 02-10-2017, 10:22 PM
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No idea, but my Heathkit GR-370 had a RCA Hi-Lite 25BCP22 that was the weakest CRT I've tested yet. No blue glow though.
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Old 02-10-2017, 10:42 PM
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When I test a gassy tube on my B&K 466 setting the cutoff knob (which states to adjust meter up by 2 divisions) will have an all-or-nothing response from the needle and there will be blue or purple glow in the neck...The worse the tube the bigger the glow.
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Old 02-10-2017, 10:59 PM
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These Hi Lite tubes (that I JUST de cataracted) both test perfectly fine on all my testers. Even on the 465, there were no anomalies when setting cutoff, and they both tested between 80 and 90 percent.
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Old 02-10-2017, 11:08 PM
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I'm pretty sure that means the crt is full of air. Why not just test a known-good tube? You know... like one that's actually inside of a working tv that you have watched recently? I know you have at least one -_-
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Old 02-10-2017, 11:09 PM
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My guess is that emissions will drop quickly under regular use, or suddenly drop to nothing when the filaments open.
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I'm pretty sure that means the crt is full of air. Why not just test a known-good tube? You know... like one that's actually inside of a working tv that you have watched recently? I know you have at least one -_-
Yeah, what he said.

If a lot of heat was used for cataract removal, it may have gotten to the guns and compromised the seal at the pins.

Last edited by Jon A.; 02-10-2017 at 11:16 PM.
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Old 02-11-2017, 06:59 AM
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I could've sworn gassy tubes glow a bright purple, not blue due to the discharge of ionized oxygen. I have some tubes that glow blue on the neck glass due to electron bombardment. Is the tester responsive at all?
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Old 02-11-2017, 08:59 AM
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That looks like electron bombardment of the glass, not a gassy tube. You probably didn't notice it before because that part of the neck was covered by the convergence yoke and other hardware. Ignoring the glow, does the tested read as you expect?

Don't ever use the rejuvenate function on the 465. It's a really crude tube killer.
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  #11  
Old 02-11-2017, 09:34 AM
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I hooked the tube up to the chassis out of the cabinet, and the tube works just fine. I also tested a Magnavox 25VCXP22, and it did not have any blue glow.
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Last edited by TUD1; 02-11-2017 at 09:46 AM.
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Old 02-11-2017, 11:08 AM
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If you've got raster your tube is not gassy (or at least not very gassy). When a CRT is full of gas you won't get a raster and the HV will probably arc to the gun and the HV system will cry bloody murder.
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  #13  
Old 02-11-2017, 06:21 PM
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Quote:
Originally Posted by TUD1 View Post
I hooked the tube up to the chassis out of the cabinet, and the tube works just fine. I also tested a Magnavox 25VCXP22, and it did not have any blue glow.
Man, I'd like to get hold of a couple of strong 25VCXP22s, or 25VBEP22s, I think only the mounting hardware is different. Two of my best sets use them.
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When a CRT is full of gas you won't get a raster and the HV will probably arc to the gun and the HV system will cry bloody murder.
Probably the same sound I heard when I fired up my Heathkit GR-2000 with the 2nd anode cap accidentally left off. It was deteriorating and wouldn't hold well anyway so I replaced it with a screw-set cap from an old RCA.

Last edited by Jon A.; 02-11-2017 at 06:26 PM.
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