12BD6 Tube

Robert Moulton rmoulton at EMAIL.ARIZONA.EDU
Wed May 17 12:46:50 EDT 2006

Thanks for the info Deane!


On May 17, 2006, at 8:21 AM, Deane McIntyre wrote:

> 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 
> versions
> 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.
> 73,
> Deane McIntyre VE6BPO

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