An NOS '49 Motorola 7VT2 TV

[EdKozk2]

Originally Posted by bandersen

Amazing score! I'm glad it ended up in your hands It looks like the knobs don't have the white crud that so often plagues these sets.



I'm not sure what you mean ? Why would this TV have a different phosphor ? Doesn't every 7JP4 have the same type of P4 phosphor ?

Hi Bob,
I recall reading in some old literature that the chemical elements for the P4 phosphor were changed in the 50's. The percentages of some the chemical elements were varied. The older crt's tend to look much yellower. I see this difference in many of the sets I have with original crts. The newer 7JP4 like I bought in 1974 looks more gray/white. I even noticed this on a 5BP4 I bought from the ETF a few years ago.
Ed

[Electronic M]

Originally Posted by EdKozk2

Hi Bob,
I recall reading in some old literature that the chemical elements for the P4 phosphor were changed in the 50's. The newer 7JP4 like I bought in 1974 looks more gray/white. I even noticed this on a 5BP4 I bought from the ETF a few years ago.
Ed

Every major manufacturer could (and some did) vary powered phosphor color... unpowered phosphor color can be as much a function of runtime as manufacturing process. If you have encountered a round tube that sat behind a square mask and was set up for minimal overscan there will be a browned center square and a blue outer ring.

[EdKozk2]

The wikipedia covers some of the P4 formulations, with and without cadmium or beryllium.

https://en.wikipedia.org/wiki/Phosphor

The table pictured is from a copy of U.A Sanabria's Television Course book published in 1948. The listing for P4 phosphors should use a plus sign instead of a minus.
Ed

[decojoe67]

The Motorola lives again! I had my friend go over the chassis. It had been professionally worked on, but with a minimalistic approach. Now it's been tweaked to be a reliable performer. The photo doesn't do the screen-shot justice. It plays like new. The audio is loud and crystal clear. Those Motorola TS-18 chassis are very good.