[Boatanchors] Wanted: Guidance for Purchase of 8122 Tubes

[Geoff]

Around mid 66 all RCA date codes had the same internal structure and are 
subject to the same caveats about screen failures.

Burle changed something in the manufacturing process as all Ive tried are a 
bit hotter by about 100W. Havent seen a bad one yet and Im using them in my 
NCL-2006.

The clones are all appearing to use washed RCA 8072's with a new anode 
cooler, I have a NIB pair of Penta's that tested out as new but not matched 
of course.

Matching is very important and a difference of up to 1.5V of bias for the 
same static Ip is acceptable.

Adding a screen current regulator plus protection against negative screen 
current is a rather simple mod.

Changing over to Svetlana 4CX400A's is not all that hard when all else fails 
or convert to a single GG 3CX or 3CPX800A7.

Carl
KM1H





----- Original Message ----- 
From: "D C *Mac* Macdonald" <k2gkk at hotmail.com>
To: <boatanchors at mailman.qth.net>
Sent: Tuesday, April 24, 2012 12:55 PM
Subject: [Boatanchors] Wanted: Guidance for Purchase of 8122 Tubes


>
> Subject really says it all, but I have seen this
> mentioned in the past. I just wonder if there is
> a "repository" of such information somewhere.
>
> Things such as "safe" manufacturers, code
> numbers on the tube, etc.
>
> 73 - Mac, K2GKK/5
> Oklahoma City
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