I just purchased a 6T5 eye tube for my 1938 zenith 12s265 console. He said it was a NOS tube that tested new.

However I just installed it and while it does show very bright and opens and closes great, The center filament glows Bright Orange at the very tip and stays that way. The center of that stem is dark / black-like and the base of the “stem” in the center is a muted / dark orange color. When I turn radio off the green goes dark first leaving the orange tip still on very briefly then it too goes dark.

It glows much brighter than my poor picture depicts it.

My Question. Is this a normal condition? Or is it actually going bad? Or is there something I can do to correct this situation.

I did own one 6T5 tube previously, but many years ago but I was guessing that the tip should not glow orange?

I thank you for your time and would very much appreciate your time of a reply to the above so I know what or why it is orange at tip, or is this normal?

Thank you

Great that you found a new 6T5. Center element is the filament. It glows orange and will be slow to cool after power is turned off. It's normal to see some filament glow.

Hi Norm,

Thanks for your timely reply. I sent you a pm by the way. I was concerned mostly because it seems the filament tip glows very bright and much brighter than my picture depicts it to be. Picture makes it appear fairly dim. So hence my concern. Bright tip filament is ok / normal then?

On mist cathode-type tubes you don't see much of the filament, since the end of the nickel cathode tube is usually pinched shut. Yours seems to have been incompletely pinched, letting you see the bright filament inside the cathode sleeve. It may annoy you, but it has no effect on operation.

Jim Cross

The color is the indicator of temperature, not so much the brightness. Your photo shows the color to be about right as viewed here. So, yours slipped by QC. Should make it extra collectible, no? Anyway, I think it's kind of cool-looking.

Edit - I stand corrected. Thanks for putting forth the effort, Norm. I still think it looks pretty cool. I've never seen one lit up in person. Anyway, see below:

I sent a PM with this site:

http://magiceyetubes.com/

Click on display patterns. The 6T5 doesn't have a cover over end of the filament so orange glow shows. Other eye tubes have end of the filament covered.

Greeting Jim,
Thanks for your post:"On mist cathode-type tubes you don't see much of the filament, since the end of the nickel cathode tube is usually pinched shut. Yours seems to have been incompletely pinched, letting you see the bright filament inside the cathode sleeve. It may annoy you, but it has no effect on operation."

Well, Thats probably the situation with mine I'm guessing? Although Norm also made the comment that this just vsries from tube to tube depending on construction. My filament tip does glow pretty bright (in my opinion anyway) and annoys me as you suggest it might. I guess I just assumed it would not show at all like my 6E5 and 6U5 tubes. Good to know from Norm and you while the glow may vary, there is nothing wrong with the tubes operation and it is a nos 6T5 in correct operating condition.

Just bothers me as my eyes are drawn to that darn red dot. I know this tube is rare, and it is nos, and it is the correct tube for this console so hate to swap it out. A friend of mine in the know said this tube could sell for as much as $300. !! - wow. I tell you though If someone offered me a nos 6U5 and $250. I'd be tempted to sell it, and install the 6U5.

Greeting mescalero
I appreciate your comment. However I don't believe it is any type of a collectors item or worth more. I can't believe they sell for $250 - $300 as it is. Thats amazing to me. I guess I never realized they were like "hens teeth". Glad you think its kinda cool looking. Wish I did.

Thanks Norm, Im glad thats straightened out as all of my 6T5's look that way including Zenith branded.

Carl

Well if you feel it's too bright, a resistor could be added to the heater line to reduce voltage, I'd start with something like 5 ohm at 5 watt... Should not effect eye operation but will defiantly reduce cathode glow...

Tom

Thanks Tom for your suggestion. Sounds simple enough. I would most probably do as you advised, ...if I knew how to. But I do not. I am but an older retiree and while I have collected many radios over the years, and own several now, - mostly zenith and a few philcos. I have no expertise on repairing them unfortunately. Not to mention my failing eyesight or less than stable hands these days.

I usually purchase restored sets now or send them to a few guys I know that have helped me reasonably in the past. Hate to send away the chassis and deal with hassle, and cost (shipping two ways and labor cost), and time that goes with it over an orange glow in the filament tip that several tell me varies in brightness and is normal. But I do hate it thats for certain.

I suppose that annoying glow in the center is the reason that tube was so short-lived, and thus is so rare. I bet the Zenith engineers and execs didn't like it either.

There is a rare Japanese tuning eye that uses the cathode glow to advantage; their type 6E5D. The 6E5D has a red plastic crystal over the cathode, and thus glows red at the center.

Jim Cross

"I suppose that annoying glow in the center is the reason that tube was so short-lived, and thus is so rare. I bet the Zenith engineers and execs didn't like it either."

Hi Tubemaster,
Not sure if they liked it? But I know I don't. Guy I bought it from wrote to say if I wanted to get rid of it he'd swap me two NOS 6U5 tubes plus $100.00 for it back. But I hate to not have a 6T5 in it and think maybe $100 is too cheap.

"There is a rare Japanese tuning eye that uses the cathode glow to advantage; their type 6E5D. The 6E5D has a red plastic crystal over the cathode, and thus glows red at the center."

Hey Jim,

I'll have to keep that tube in mind in case I happen across one. But correct me I'm wrong but from how you describe it, Then that tube would have an even Larger RED circle glowing in the middle of the eye?

Ray

I would not drop the filament voltage below 5.9V otherwise higher than expected emission degradation is likely to occur. Overvoltage is also bad and the best point for long life is about 3% below the 6.3V target value or 6.1V. Thats also a benefit of using a bucking transformer as it reduces all voltages.

Carl

I really doubt that emission degradation would be a problem when running these tubes at a reduced filament voltage. The target area is what gets used up causing them to get weak, it is not usually caused by a lack of cathode emissions.

You can test one on a tube tester and the emissions will still be great but they will hardly glow.

Dave

Enough. If you can find some Phool that will pay you $150 for the tube, send it away. There are 12 volt surplus eye tubes that you can adapt that will be just as good to help you tune your radio. Of course if you are deaf, this would be easy if you are deaf, hard if you are blind, but I fail to see the ultimate benefit. For what purpose?

Plenty here or on web. So far as I know, nobody is making new eye tubes, but I could be wrong.

This is good advice for your Zenith !!
It will lead to a long and happy tube radio life. (Once recapped)that is,
Peter

I seriously doubt a low current eye tube will have a noticeably degraded life if operated at 5v, I wouldn't try that much drop on higher current tubes though...

(runs off to tube tester to see just how low heater voltage can be reduced before it causes a noticeable difference in operation)

No this won't give any hint of longevity but now I'm curious on just how much voltage could be reduced before operation suffers...

Any guesses???

Tom