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Old 17th February 2011, 01:53 PM   #1
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Default eimac 152TL and 304TL

Hi all,

I have a question for the Eimac tubes experts. I won auctions for 304TL tubes on e-Bay and received some of them with defective filaments. I mean one of the two filaments of the tubes is open and i was wondering if one could consider such half heated 304TL as a 152TL tube

Thanks for your information.

Regards,
Facelvega
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Old 17th February 2011, 02:00 PM   #2
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just use paypal to get your money back and put em on display .
it seems to me its not hard to test a tube whit a multimeter for fillament resistance ........
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Old 17th February 2011, 02:24 PM   #3
Gluca is offline Gluca  Italy
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Quote:
Originally Posted by facelvega View Post
Hi all,

I have a question for the Eimac tubes experts. I won auctions for 304TL tubes on e-Bay and received some of them with defective filaments. I mean one of the two filaments of the tubes is open and i was wondering if one could consider such half heated 304TL as a 152TL tube

Thanks for your information.

Regards,
Facelvega
I never succeeded in running 304TL with half filament. Bad news is that most probably the other half will die shortly (well ... it happened to me twice).
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Old 17th February 2011, 04:31 PM   #4
Knarf is offline Knarf  Denmark
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Quote:
Originally Posted by facelvega View Post
Hi all,

I have a question for the Eimac tubes experts. I won auctions for 304TL tubes on e-Bay and received some of them with defective filaments. I mean one of the two filaments of the tubes is open and i was wondering if one could consider such half heated 304TL as a 152TL tube
Yes you can.

The 304TL has a fun background story. During the early part of WW-II, the US military needed a tube suitable as a pulse modulator for one of their radar systems (naval, I think...). Eitel & McCulloug, later Eimac, was tasked with developing a prototype (at all cost and preferably yesterday). They already had a triode design, which seemed appropriate, and it was sent in for evalution. It was called the 75TL. Unfortunately it wasn't powerful enough, so E&M put two 75TLs in one bottle and called it a 152TL.

Still not quite big enough, they doubled it again to a 304TL. And the man was pleased.

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I never succeeded in running 304TL with half filament. Bad news is that most probably the other half will die shortly (well ... it happened to me twice).
Have never tried that, but wondering what heating arrangement you used? If you use 10V filament power, then you will overload the surviving half of the series/parallel filaments in short order for sure.

If only one filament is broken, then running half the tube at 5V should work, unless having the first filament break might mean the remaining 3 has been overloaded somehow.
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Old 17th February 2011, 05:49 PM   #5
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Hi guys,

Thanks a lot for your feedback

Sure i could return the items to the e-bay sellers and try to get money back but i thought i could have some fun running the 304TL as 152TL...

I will let you informed soon after i try

Facelvega
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Old 17th February 2011, 10:58 PM   #6
Gluca is offline Gluca  Italy
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If only one filament is broken, then running half the tube at 5V should work, unless having the first filament break might mean the remaining 3 has been overloaded somehow.
Problem was that the 304TL didn't bias properly
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Old 17th February 2011, 11:34 PM   #7
Knarf is offline Knarf  Denmark
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Problem was that the 304TL didn't bias properly
That is a pilot error, not a problem with the tubes...
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