RE21FBP22 on ebay
 

Just posted.

http://cgi.ebay.com/ws/eBayISAPI.dll...&category=3638

I can't believe nobody has bid on this
 

if this is a "RE", that means rare earth, dosen't it?, I'm surprised no one wants it.

Jack,
I think it refers, as mentioned in the discription, that the tube is rebuilt. No other technical info or picture was supplied. Maybe this put some people off.

This was recently discussed, here or on another site, regarding the "RE". The consensus (and my belief) is that it mean rare earth. What would turn me off on this auction would be the zero feedback, no pic, brief description. If I lived near the seller it would be worth further investigation, though, as this could be a great crt.

I think the "RE" prefix was only used by Sylvania.

RE?
 

Chad,
Do you know? Does the prefix "RE" in Sylvania's tube refer to Rare Earth phosphor or to REbuilt tube. I thought all 21FB & 2IFJ's contained "rare earth phosphors" (a marketing term)? Also weren't sulfide and rare earth phosphor tubes the same thing? Meaning that they had an improved red phosphor that more closly matched the blue & green phosphor in brightness value.:cool:

[quote}Meaning that they had an improved red phosphor that more closly matched the blue & green phosphor in brightness value.[/quote]

I thought it was the green phosper that was changed in later CRTs. The new green was brighter, but was also a bit more yellowish. Which means that the colors rendered would be slightly wrong. And it would also mean that there would be some colors (pure greens mostly) that could never be displayed correctly, even if the color matrix circuits were tweaked to make most other colors come out right. The original phospers were selected to closely match the color response of the human eye and brain. This is called "coloremetry(sp)". when the human eye sees yellow, the wavelength of the color yellow generates a partial response from the red receptors and another partial response from the green receptors. TV cameras use optical color filters that resemble the eye's receptors response to get the red, green and blue signals. Which then get encoded into NTSC, and then decoded by your TV set circuits. The CRT's phospers create a mix of green light and red light that then tickle your eye's red and green receptors to the same levels as real yellow light would have. Then your brain thinks it's yellow light. But if you send the light from the CRT thru a spectrascope, it looks quite different than real yellow light would. Other animals with color vision with differing color receptors in their eyes would see goofed up colors on our color TV sets even though the TV set looks fine to us. But only humans buy TV sets, so it's not an issue.... :D

I'm not sure what Sylvania's RE designation means...It seemed like all the Syl. tubes had this in front of the tube number but will really need to check my Syl. tube manual to see.

The rare earth minerals in the phosphors are yttrium or ytterbium oxide, maybe europium...rare earth is not a marketing term, I have seen in it in scientific texts. I guess it probably relates to the rarity of these elements in ores and such.

The change in green was a mandated safety issue, NO CAD GREEN, is what it was called at Philips where I worked in the CRT lab, the removal of cadnium from the green phosphor, shifted green toward yellow. This was done about 1990.

...

Sulphide-Rare Earth Phosphor
 

Thanks to all for the various explanations. However,I'm still a bit puzzled? The 21FB and 21FJ were all-sulphide tubes. As I understand it this provided higher brightness levels and provide a red phosphor that was nearly equal in brightness to the green and blue phosphors. Were the tubes with "rare earth phosphors" different from the "all sulphide" tubes? Is sulphide a reference to the red phosphor only? I understand that the term "rare earth phosphor" is a chemical/scientific reference. But its almost magical and mysterious sound compared to the dull sounding term "sulphide" was used frequently in ads to hype the higher brightness and more vibrant color.