I just received a 12LP4 with a damaged base and was surprised to find this inside.

It looks like the base is pressed glass and has a pinch off vacuum seal made from two types of metal.

https://farm6.staticflickr.com/5277/14381888410_d7a4d876c9_z.jpg (https://flic.kr/p/nUSWnh)

Pretty sure every other one I've ever seen is a glass nipple like this mangled 12QP4
https://farm3.staticflickr.com/2863/8798933687_7f7a3d5dc8_z.jpg (https://flic.kr/p/epwQre)

It still has some life left :)
https://farm6.staticflickr.com/5552/14568574665_d2d4e1ea03_z.jpg (https://flic.kr/p/ocnKFP)

https://farm4.staticflickr.com/3864/14565193221_2b842047a3_z.jpg (https://flic.kr/p/oc5qv4)

Does it have continuity to any of the normal connections, by chance?

I can't tell from the full rez photos, but it looks like an extremely well done rebuild, or I'm just seeing a step line in the neck where they shifted glass types to match the stem to the bulb. Confirm/Deny that it is a rebuild?


I seem to have memory of seeing this "HVAC" style seal on some mid 90s vintage Toshiba projection set tubes when I went to air them up before disposal. (This was 2005, they had terrible burn-in among other things, so no great loss to society in my opinion... The only unit I actually regret being party to disposal of was the Dimensia.)

I haven't checked for continuity to any pins. I'm pretty sure it's not a rebuild. It has an RCA base and neck markings and the Admiral stamped on the bell indicates it's the original that came with the 1949 TV.

I don't have any hard data, but some considered the copper pinch off to be better (but more expensive) than the glass tip seal, since hot glass can outgass during the sealing process.
The 15GP22 has a copper pinch.

jr

I've seen this in some early (like 46-48) 10BP4's.

Some color roundie CRT's have those also

https://www.youtube.com/watch?v=aU-Jhmdl-MU

I haven't checked for continuity to any pins. I'm pretty sure it's not a rebuild. It has an RCA base and neck markings and the Admiral stamped on the bell indicates it's the original that came with the 1949 TV.
According to tube lore, RCA came out with the 12LP4, sometime in 1948.
That must be one of the earlier model 12" Admiral's.
Is that one of the two chassis models?
BTW, is that the original reading or did you rejuvenate it? :scratch2:

It's a single chassis. I just bought the bare 20Y1 chassis and CRT.
Admiral only used that chassis in four models 20X136, 145, 146 and 147. All came out in 1949. I'll be putting it into a 20X136.

No, I did not rejuvinate it.