An interesting (if useless) find

[Dave S]

Got this CRT from a fellow collector the other day. He told me thought it might still be good, so I was all excited, but clearly the vacuum has all leaked out

It's a 15HP22, the much less common cousin of the 15G.

[Phil Nelson]

Interesting. The label says Engineering Sample. Was that tube used in any production sets?

Phil Nelson

[miniman82]

Used in the RX-90:

http://earlytelevision.org/cbs_rx-90.html

[John Folsom]

I have seen 3 15HP22s, including Dave's. They all had engineering sample labels on their neck.

I have also seen several CBS RX90 15" sets, which were designed to use the 15HP22 (according to the schematic). The RX90s were also all labeled as engineering samples.

So I speculate that Hytron, who made the 15HP22, and was owned by CBS, knew that in several months (summer of 1954) they would be releasing the 19VP22, so they and CBS only released the 15HP22 in very limited quantities, and probably none of them were used in commercially produced sets sold to the public. And CBS knew they would be releasing the CBS model 205 using the 19VP22, so all their 15" sets were labeled as engineering samples to prevent them from being sold commercially.

[stromberg6]

Darn shame that it went to air, but still is an interesting artifact, IMO. Love that RCA had to pay royalties to CBS for the use of the screening process. That really must have frosted General Sarnoff .

[Dave S]

A sticker on the side would seem to indicate that this was installed in the Westinghouse set:

[John Folsom]

That may or may not be so. All the Westinghouse sets I have known have had 15GP22s in them. But it is certainly possible that Westinghouse ( and who else?) had engineering sample 15HP22s installed in their sets. But it is also possible that the CRT and Mu-metal shields came from separate sources... Who can say?

Still, it is exciting to see another EXTREMELY RARE 15HP22 CRT surface, whether good or dud!

[miniman82]

John, don't you have one of these tubes?

[Pete Deksnis]

I'm hoping it makes its way to an ETF display.

[Dave S]

Originally Posted by John Folsom

it is also possible that the CRT and Mu-metal shields came from separate sources... Who can say?

John,

I'll have to take a closer look and see if there are any tell-tale clues but my first impression was that the parts look like they've been together since dinosaurs roamed the earth.

-- Dave

[Electronic M]

Wow, those are the first pictures I've seen of that tube! I've read a good bit about it, but never seen any pictures of it before.

I'm curious how you determined that air leaked in. Were the getters white, did the neck light up purple when you tested it(if you tested it), or did something else indicate loss of vacuum?

[David Roper]

Isn't that a white getter plainly visible in the first picture? I assumed it was.

[Username1]

I was wondering how you knew it had no vacuum also....? I can't seen anything indicating loss in the pictures..... Anyway, does it look like the assembly process is the same for this tube as the rca tube? Same sources for vacuum leaks?

[Dave S]

[Dave S]

The guy I got it from thought that the blackening on the glass near the socket might be good getter indicating that only some air had gotten in. I'm not sure what that darkening is (Edison effect?) but that's not where I'd expect to see getter material and the condition of the "real" getter would indicate that the vacuum is completely gone.