[ARC5] A Tube Puzzle

[Richard Knoppow]

----- Original Message ----- 
From: "Kenneth G. Gordon" <kgordon2006 at frontier.com>
To: "J. Forster" <jfor at quikus.com>; <jfor at quikus.com>
Cc: <Arc5 at mailman.qth.net>
Sent: Monday, April 30, 2012 2:25 PM
Subject: Re: [ARC5] A Tube Puzzle


> On 30 Apr 2012 at 14:02, J. Forster wrote:
>
>> Hi,
>>
>> My understanding was that standard tube conventions had
>> the leading
>> digit(s) as the filament voltage:
>>
>> 1B3   = 1 V
>> 2X2   = 2 V
>> 5Y3   = 5 V
>> 6X5   = 6 V
>> 12AX7 = 12 V
>> 35W4  = 35 V
>> 50C5  = 50 V
>> 117L7 = 117 V
>>
>> etc.
>>
>> How does a 2C51W dual triode fit in? It has a 6 V
>> filament?
>
> How about the loctals, all of which start with either 7 or
> 14, and yet have 6.3
> v and 12.6 volt filaments?
>
> Ken W7EKB

     I can't find the characteristics of the 2C51/5670 but 
suspect its a transmitting or special purpose type although 
it looks like a conventional dual triode.  The system of 
specifying tube type numbers was established in the early 
1930s at a time when there was a profusion of new tubes and 
no systematic method of numbering them at all. 
Unfortunately, it didn't work that well partly because there 
were too many new types and some of them did not fit any of 
the catagories in the original numbering scheme. Locktal 
tubes are among these. They followed approximately the 
original system by using approximate filament voltages. 
Philco also made tubes with non-standard types like XXD and 
XXL.
     Transmitting and special purpose tubes do not seem to 
have ever followed any system, nor did Western Electric for 
their tubes.
     The four digit number system used for ruggedized, 
military, and other specials also follows only a rough 
separation of types, my memory is that long-life tubes have 
six-thousand series numbers.
     The W following the type indicates the tube was made 
for a government contact or contractor.  It may or may not 
have had to meet other than standard tolerances.


--
Richard Knoppow
Los Angeles
WB6KBL
dickburk at ix.netcom.com