[R-390] 12BA6

[Shoppa, Tim]

AI4NI writes:
> The 12BA6 is not a JAN tube.
> It is just a commercial tube. 6BA6 stuff with a 12 volt heater running at 
> 1/2 the 6 volt current. The couple Europe numbers are the only matches.

I once specifically looked to see if there was a mobile or ruggedized 12BA6 for vehicular use. After all GE etc had a line of industrial/vehicular rated tubes and they also sold mobile radios. I was a little surprised to see no ruggedized 12BA6.

> Lots of pentodes that come close in pin configuration and performance.

I once tried randomly swapping 6BA6's with 6AK5's and 6AU6's and some other similar pinout pentodes.

In the R-390A I observed very little difference in usability from doing this with just a single tube, even in IF and RF stages.

Changing one IF or RF pentode for a different kind would result in the carrier level meter working a little differently but AGC mostly seeming to work OK. Changing the cutoff characteristics of multiple IF tubes did impact AGC usability.

Tim.