Two 15GP22s At TheBay

[TubeType]

Here are two 15GP22s I found for auction at TheBay.
Happy Holidays,

Terry Cheek

http://cgi.ebay.com/ws/eBayISAPI.dll...E:B:SS:US:1123
http://cgi.ebay.com/ws/eBayISAPI.dll...E:B:SS:US:1123

[newhallone]

I am dying to here the comants on these.

[Charlie]

FRAUD! FRAUD! FAKE!

Nah, I'm just kiddin!

It's interesting he mentioned it looks as if someone has rebuilt one of them. Wow... if that's correct, I wonder how many years back that was done?!

[Eric H]

I'll make one comment

"my CRT tester will not test this CRT"

If I had a $2000-$3000 CRT I'd find a tester that would test it, won't most of the B&K's do it if you use some alligator clips?

He's in N.J. I'm sure someone here would be happy to go test it for them?

[jr_tech]

Originally Posted by Charlie

It's interesting he mentioned it looks as if someone has rebuilt one of them. Wow... if that's correct, I wonder how many years back that was done?!

I really wonder about that "rebuild"... look at the label on the tube... looks original factory to me. Did somebody carefully remove the label, rebuild the tube, then put the label back on the tube? Perhaps it was just a factory "re-neck" ?

I have never seen a listing for that gun type in any of the Superior Electronics catalogs that I have been able to find.

jr

[radio63]

Originally Posted by Eric H

I'll make one comment

"my CRT tester will not test this CRT"

If I had a $2000-$3000 CRT I'd find a tester that would test it, won't most of the B&K's do it if you use some alligator clips?

He's in N.J. I'm sure someone here would be happy to go test it for them?

The Sencore CR-70 will test a 15GP using the universal test adapter it comes with. That's what I have and that's what I have tested my 15GP22s with.

Gilbert

[Charlie]

Perhaps this would have been the grandfather of all RCA Colorama tubes!

[Dave A]

I have a 15GP22 adaptor I made for my Beltron. I am near the seller and sent a note asking to visit to check the tubes. Stand by.

[Robert Grant]

Question about testing a CRT in unknown condition:

If a CRT has gone to air, but nobody has powered the filament since before the vacuum was lost, could such a CRT be restored to operation by re-evacuating the tube, without have to do a total rebuild (assuming any leak would be extremely slow or could be found and closed)?

I say this, because I wonder if a test of an unknown CRT should start with a very low voltage continuity test of the filament, then, if there is any conductivity, doing some type of test for any presence of air in the tube.

Rather than just hooking up the tester, which would destroy the gun of the tube if in fact the tube had gone to air?

[Eric H]

Originally Posted by Robert Grant

Question about testing a CRT in unknown condition:

If a CRT has gone to air, but nobody has powered the filament since before the vacuum was lost, could such a CRT be restored to operation by re-evacuating the tube, without have to do a total rebuild (assuming any leak would be extremely slow or could be found and closed)?

My understanding of it is no, once the cathode has been activated exposure to air destroys it.

I'm sure someone who really knows the answer to this will chime in.

[Phil Nelson]

Testing an unknown CRT is certainly a common scenario. Perhaps one of the sages could tell us all what the potential risks might be.

Phil Nelson

[kx250rider]

I'm not too surprised, as I've seen a good share of 15GP22s on eBay. I sold 4 or 5 of them myself, in various states of condition. I've seen rebuilt ones, but likely rebuilt in the 50s. In fact, these two tubes may have come from me. I sold two of them to a collector Back East about 10 years ago, and one was a rebuilt.

Charles

[jr_tech]

Originally Posted by Robert Grant

I say this, because I wonder if a test of an unknown CRT should start with a very low voltage continuity test of the filament, then, if there is any conductivity, doing some type of test for any presence of air in the tube.

Rather than just hooking up the tester, which would destroy the gun of the tube if in fact the tube had gone to air?

When I first powered up my 22EP22 after sitting for 15+ years, I did just that, and brought the heater voltage up slowly. I did NOT want to see a flash from the heater that would indicate that I had destroyed the tube!

I was fortunate, the heaters appeared to power up normally. Had they not, I really had no game plan, and I doubt that the tube could have been saved anyway... Perhaps long term low voltage on the heaters would "pump" the tube somewhat... perhaps the getters could be "re-flashed"... but at least the heaters would be intact for further experiments.

jr

[jeyurkon]

During the activation of the cathode BaCO3 is dissociated to BaO. Subsequent heating at a higher temperature then reduces some of the BaO to Ba with the help of a reducing agent like Si. When the tube goes up to air the Ba oxidizes back to BaO or BaO2. Mostly BaO I believe. There are other alkali's involved too, but Barium is the major one.

You would need to reactivate it, but the reducing agent should have been mostly used up during the first activation.

There would a significant expense in trying it, with no way of knowing the status of the cathode before hand. I don't think it would be worth it. If I spent that much I'd want to know that I had a fresh gun in the end.

John

[Dave S]

Originally Posted by jr_tech

I really wonder about that "rebuild"... look at the label on the tube... looks original factory to me. Did somebody carefully remove the label, rebuild the tube, then put the label back on the tube? Perhaps it was just a factory "re-neck" ?
jr

I've seen the tubes. The one with the weld on the neck definitely looks like a old rebuild. Or a "re-neck" but what's a re-neck? This is the second one I've seen like that. Untested unless Dave A or someone gets over there, but I can vouch that they're absolutely for real and lookin' good.

--Dave Sica