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Hi,

Wynona said:

We had one of those on the bottom in the 1940s! It was a Philco. When we turned it off, it took a long time for the bright dot in the middle to finally extinquish itself.

That is a tuning indicator AKA a "Magic Eye". The reason it takes so long to extinguish (or that's what you think) is that is contains a fluor coating which absorbs light. Just like older analogue watches that had the ciphers coated with fluorescent matter so you could still see the time in the dark.

So much for the anecdote.

Cheers,

fdegrove said:

Hi,



That is a tuning indicator AKA a "Magic Eye". The reason it takes so long to extinguish (or that's what you think) is that is contains a flour coating which absorbs light. Just like older analogue watches that had the ciphers coated with fluorescent matter so you could still see the time in the dark.

So much for the anecdote.

Cheers,

Interesting... But I never knew flour was fluorescent! [phosphorescent, right?] But, yeah, still interesting, I remember seeing that smudge at lights and TV off.

[

Originally Posted by Wynona
We had one of those on the bottom in the 1940s! It was a Philco. When we turned it off, it took a long time for the bright dot in the middle to finally extinquish itself.

fdegroveThat is a tuning indicator AKA a "Magic Eye". The reason it takes so long to extinguish (or that's what you think) is that is contains a flour coating which absorbs light. Just like older analogue watches that had the ciphers coated with fluorescent matter so you could still see the time in the dark.

So much for the anecdote.

* Most TV's * then had rotary coil tuners like a Collins R390 military radio back then and some of the others all this went digital decades later.

The cat eye tubes were more for radios and later tape recorders because at the time they were cheaper than a meter .It's more likely her TV was Post war set direct view TV and most of those had rotary coil tuners on the TV's although a few did not


Maybe she had a Radio TV combo with a cat eye tube or pilot light or it was the CRT emitting when it was cooling down & discharging some of those old dogs would show a prolonged white dot in the middle of the screen when you turned then off and I don't think they had any parallel branch circuits to drain off excess voltage spikes at [set off] .

IIRC the later aluminized CRTs helped with brightness a lot by keeping the light going forward and not reflecting into the CRT envelope behind the phosphor coatings .


Wynona, FYI on the cat eye tubes :

Magic eye tube


A magic eye indicator, called in technical literature an electron-ray indicator tube,[1] is a vacuum tube which gives a visual indication of the amplitude of an electronic signal, such as an audio output, radio-frequency signal strength, or other functions.[1] It is also called a cat's eye, or tuning eye in America. Its first broad application was as a tuning indicator in radio receivers, to give an indication of the relative strength of the received radio signal, to show when a radio station was properly tuned in.
- wikepedia-


The eye tubes were developed as a cheaper alternative to the needle movement metersThe "magic eye" valve for tuning radio receivers was invented in 1932 by Allen B. DuMont (who spent most of the 1930s improving the lifetime of cathode ray tubes, and ultimately formed the DuMont Television Network).[5][6][7] It is a miniature cathode ray tube, usually with a built-in triode signal amplifier. It usually glows bright green, (occasionally yellow in some very old types, e.g., EM4) and the glowing ends grow to meet in the middle as the voltage on a control grid increases. It is used in a circuit that drives the grid with a voltage that changes with signal strength; as the tuning knob is turned, the gap in the eye becomes narrowest when a station is tuned in correctly.
The RCA 6E5 of 1935 was the first commercial tube
Magic eye tube - Wikipedia, the free encyclopedia
-wikipedia-

fdegrove said:

Hi,

Wynona was probably referring to the TV screen. I thought he meant the receiver next to it on the right which seems to contain a magic eye as a tuning indicator.
Guess I jumped the gun.

I designed valved electronic devices for years BTW. Almost as much fun as fiddling with W10 LOL.

Cheers,

BTW, are we all that old ??

I worked on TV and radios early on in life before changing careers .I can still bench a flat panel or a lot of other stuff even though I worked on the old delta gun sets in the early 70's long before flat panels .

We had 3 CRT color jigs in the shop for the chassis pulls out of the big console sets back then instead of hauling the big sets in for bench work that would take up lots of moving labor and space .

fdegrove said:

Hi,



Yes, it's phosphor which is a fluorophore. Not fluor, which I think is called fluorine in English ?
Anyway, sorry about that.

Cheers,

It absolutely not a problem, fdegrove. We have lots of fun in my household as we speak English, Flemish, and French! Lots of teasing and word games....