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[AMPS] tube structure/failure.

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Subject: [AMPS] tube structure/failure.
From: (Phil Clements)
Date: Wed, 07 May 1997 17:16:16 -0500
At 05:28 PM 5/7/97 utc, you wrote:

>See you at Dayton. I'm usually in the flea market dealing with
>people with names like Fleamarket Fred for a "brand new" 4-1000.

I have had to add a new weapon to my flea market shopping bag, especially for
ceramic tubes represented as "NEW". It is a good magnifying glass. You can
easily see the marks made on the tube pins by the socket and by the plate
cap on the anode if it has ever been fired up since leaving the factory.

On the Eimac glass tubes, in addition to the above, the bright red lettering
on the glass turns brown after a few hours in service. A really
tube will accumulate a brown opaque substance around the bottom of the glass
envelope that the OT's refer to as "lace". Just a few hints to take along
with you to the next flea market. I have run 4-1000A tubes that were
full of lace (broadcast pulls) that lasted me for years, but the price of
these beasts should be adjusted accordingly!

Good hunting; caveat emptor!

Phil, K5PC

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