12BD6 Tube

Deane McIntyre dmcintyr at UCALGARY.CA
Wed May 17 11:21:21 EDT 2006

On 17-May-06, at 8:09 AM, Robert Moulton wrote:

> Does anyone know whether a 12BD6 is a direct replacement of a 12BA6?
> I recently found one in place of the 12BA6 in a Hallicrafters S-38E  
> I am working on. The replacement was an RCA tube. All the info I  
> have, which is limited, shows that they are similar but not a  
> direct replacement. I am currently borrowing a tube from another  
> radio for testing and will probably put in a 12BA6 anyway, but was  
> just curious for future reference.

The 12BD6 is a lower gain version of the 12BA6 and should work but being
lower gain the 12BA6 would be better. The xBD6 tubes are miniature  
of the xSK7 octal tubes, while the xBA6 tubes are miniature versions of
the xSG7 tubes, more or less.

A common mod to the older Halli and other receivers that use the octal
6/12SK7 for the IF stage was to replace them with a 6/12SG7. Gives  
more gain but beware
that the increased gain may cause the IF stage to oscillate.

The 19HR6 gives even more gain than the 12BA6, the filament current
(150 mA) of both tubes is the same so they can be interchanged in
series string circuits. Was sometimes done to "hot rod" AA5 radios.
Again, watch out for possible oscillations in the IF stage.


Deane McIntyre VE6BPO

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