[Hallicrafters] microphonics

[Carl]

----- Original Message ----- 
From: "Walt Cates" <cateswa at msn.com>
To: <W4AWM at aol.com>; "HallicraftersRadios" 
<HallicraftersRadios at yahoogroups.com>; "hallicrafters" 
<hallicrafters at mailman.qth.net>
Sent: Sunday, November 20, 2011 10:51 PM
Subject: Re: [Hallicrafters] microphonics


> HI John,
>
> I have "heard" (before my time as a tech) that after the war and deep into 
> the 50's that tube quality went down. With out the military paying high 
> dollars for gear and parts the tube makers found it difficult producing a 
> quality product for reasonable price. But here again as you said that was 
> the fault of the tubes and not necessary a design flaw in the rigs.
>
> Best Regards, Walt Cates, WD0GOF,

>From personal experience Id say that is very incorrect. In 51-53 there was 
Korea which did cause some limited availability and later the Cold War kept 
military stockpiles full. Standard JAN tubes were the same as consumer 
production while the W versions were different.

Qualtity DID start to fall in the mid 60's by RCA (wide performance 
variations) but Sylvania, GE, Amperex, Telefunken, and a couple of Japanese 
brands were excellent thru to the end.

One major cause of tube degradation with the miniatures was heat. Equipment 
manufacturers ran them close to maximum and then added shiny shields to make 
it worse. When B+ was reduced by design reliability went up and performance 
did not suffer. Ive had many late models come thru the shop and the original 
Hallicrafters branded tubes were often testing almost as new.

Carl
KM1H