[Milsurplus] Strange Eimac 4-125 Tubes

[sdaitch at ibb.gov]

Jerry,

my gut feeling thought on this is that the filament strand 
has broken (opened up ) and a loose end of the filament 
strand has made physical contact with the grid.

The could explain the open between 1 and 5 and continuity
between 3 and either 1 or 5.



73
sheldon
WA4MZZ

----- Original Message -----
From: "Jerry B." <n6aj at comcast.net>
Date: Tuesday, March 22, 2005 9:18 am
Subject: [Milsurplus] Strange Eimac 4-125 Tubes

> In going throught some boxes in the garage and came up with a sizable
> quantity of NOS 4-125's.
> I have no equipment to test them in. The best I could do is check the
> filaments for continuity.
> 3 different Brands: Penta Labs, Lewis and Kaufman, and Eimac. The 
> Penta Labs
> and Lewis and Kaufmans tested OK for filament continuity. 2 of the 
> 5 Eimacs
> checked OK. However, the other 3 did not. The filament pins are 
> supposed to
> be pins 1 and 5. The other 3 dont have continuity between pins 1 
> and 5.
> Instead there is continuity between pins (1 and 3) or (pins 5 and 
> 3). Pin 3
> is supposed to be the control grid.
> 
> Has anyone ever run across this problem?
> 
> These are Military Surplus. The Penta Labs and Lewis and Kaufman 
> are marked
> as 4D21 which is the Military number. The Eimacs are marked as 4-125.
> 
> 73s
> Jerry
> N6AJ
> 
> 
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