An interesting (if useless) find
 

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.

http://i1326.photobucket.com/albums/...psf543380e.jpg
http://i1326.photobucket.com/albums/...ps9cf23e22.jpg
http://i1326.photobucket.com/albums/...ps5ff3efb9.jpghttp://i1326.photobucket.com/albums/...ps151e286d.jpg

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

Phil Nelson

Used in the RX-90:

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

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.

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 :D.

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

http://i1326.photobucket.com/albums/...ps6209385b.jpg

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!

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

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

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

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?

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

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?

http://i1326.photobucket.com/albums/...ps3624a7f6.jpg

:pity: :pity: :pity:

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.

I see.... Well maybe someone turned it on and as the filaments burned out they left a blackened spot....? I've seen it in light bulbs as they go bad. Is there continuity on the filaments? My ctc5 is dark like that near the base, I just thought the getters were down there......? Is it normal...?

I was wondering about this as well. If it does not have that same ridiculous glass->metal->metal->glass bond ring around the screen then it might be a heck of a lot easier to rebuild it...Thus getting another rare 1954 color set working.

The 15HP22 unfortunately has the same envelope construction as the 15GP22.

Thanks for sharing Dave. Working or not, it's always good to find examples of these early tubes surviving the years. Super photos.

See now if I had a time machine I could go back take a few of those dud tubes take a newer tube get the design fixed back in '53 and we would be up to our ears in working 15G based sets.....

In short, we should be working on building a time machine, not rebuilding dud 15gp22's

I think if I went back in time I would have named the tube 15SQ22 for "Improved Design by the Squirrel"

Thanks also for posting the picts and the replies!

Check Ohms
 

Would be interested if you still have continuity on the filaments ?

Is the visible mounting hardware typical of Westinghouse?
Interesting to note "E4" on the base, neck, and neck label. And all in a row.
The neck label says "regular order".
In the first pic, to the right of the riveted seam of the metal shield, is some writing. What might it say?
Phil

We have a prototype Westinghouse set at the museum. It is possible that it once had a 15HP22 in it, but there is no way to find out.

Another interesting thing. The CRT shields were apparently labeled with the same serial number as the cabinet backs. We have 6 of these numbers in our database, ranging from 005284 to 006226 (the number on Dave's shield). This might indicate that his tube was fitted in one of the later sets rather than a prototype.

The date on his tube is April of 1954, which is the same month that Westinghouse started selling the set.

Didn't the Westinghouse become available sometime in February?

Well, we are both off by a month. It was first sold in March.

http://hugelolcdn.com/i700/53403.jpg

I have meditated on the subject and have released the inner energy of my multimeter into pin 1 however no enlightenment was experienced at pin 20.

In other words, I guess it leaked while in service and the filament burned out.

The HV cable assembly looks like a Westinghouse (note the in-line connector the plate cap of the 6BD4).

Steve, Got to give this one to Dave Roper by a nose. The earliest dated ad I have offering the Westinghouse 840CK 15 for immediate delivery was the N.Y. Times, Feb. 28, 1954.

-Steve D.

15H Tube
 

I am assuming that this tube has a metal cone and glass face, similar to the 15G. Also, that this seal would be the likely cause of going to air.

Correct?

Forgive me for not remembering, but would this tube be a possible rebuild candidate, if that ever happens at ETF? :scratch2:

John Folsom had said:

Therefore the big problem in dealing with the welded flange is the same on this tube.

The difference is the screen. The design of the 15G apparently makes it susceptible to problems during the rebuild process. According to miniman82, the mass of the screen inside the 15G makes the ramping of heat during the rebuild process a pretty ticklish affair. This tube has a conventional screen, so based on what I've heard from the experts, I'd guess the 15H would have a greater likelihood of a successful outcome. As long as the leak problem can be solved. Nick? Jerome? Bob? Steve? Please correct me if I'm wrong.

Dave, I think that's correct. The internal design of the 15H shares more in common with the 19V and 21AX than it does with the 15G, though any rebuild attempt on any tube seems tenuous at best these days... I tell ya, these next 7 years can't go fast enough!

Wrong, but close. The 15G has a glass cone(and I'd assume it is the same for the 15H). The face of any color tube is attached to the cone fairly late in the manufacturing process because the shadow mask has to be installed and before that the screen has to be coated in phosphor....Neither of which is practical with the screen bonded to the cone. It would be like building a ship in a bottle.
The thing is that if they heated the glass enough to fuse it would burn the phosphor and warp the shadow mask. To deal with that issue they built the cone and face with metal rings bonded to the glass where the two pieces of glass would have normally have been bonded to eachother in a monochrome CRT. They would then phosphor the screen, insert the the shadow mask then seal the face to the cone by using a special low temp welder to fuse the metal rings together.

The rings were soon done away with in favor of low melting temp 'frit glass' which was much less leak prone then the metal to metal and metal to glass bonds of the rings.

The only metal cone CRTs I'm aware of are the pre-15G developmental types (the 4 digit designations of which escape me at the moment), and the production type 21AXP22.

All metal cone(and tubes with metal to glass seals) CRTs were very leak prone and not long after they were developed they fell out of vogue because of that.

You know, it is always easier to see someone else's mistake (RCA) than one you (CBS) made. I had always assumed that Goldmark's Laboratory made the first 15HP22's the RCA way and by doing so, quickly realized that there was a better way. However, looking at the patent, we can see that it was filed June 1, 1953 (and granted Sept 28, 1954), so Dave's April 24, 1954 tube is obviously manufactured well after the patent application.

http://www.freepatentsonline.com/2690518.pdf

The "engineering sample" notation may also have been for legal reasons to protect the CBS patent.

This difference probably explains why even though the 15GP22 and 15HP22 were mostly interchangeable, they got a new tube number.


This patent expired in 1971 and CBS thanked Goldmark, by shutting down his Laboratory in 1972.

James

Might not be usable with the same bezel/safety glass, or with the same convergence circuits/components, therefore had to have a different number.

The 15HP22 was electrically and mechanically compatible/interchangeable with the 15GP22. The only noticeable difference was the 15HP22 required somewhat less AC convergence correction waveform due to the curved shadow mask and curved phosphor dot screen.