[Drake] 6JB6A tubes

[Garey Barrell]

Darrell -

Yeah, I imagine they had several suppliers, so that might account for 
the variation.  There were some very "creative" tube manufacturers, 
without a lot of experience, during those years!

I heard a story once that the Chinese manufactured tubes had some early 
problems because the production workers who built them, by hand!, got 
creative with all those little support wires and leads, making each one 
a "unique work of art"....  :-)  Ok for audio perhaps, but a bit of a 
problem for RF......

That was one of the major factors in US made tubes, they were made by 
machine, obviously held to very tight tolerances because of the 
extremely close spacing of modern, high gain tube elements.  This 
enabled the user to plug in a new tube, even in RF circuits, and obtain 
the same results.

There's always a danger when you take a device designed to work at 15 
kHz and decide to use it at 29 MHz...

73, Garey - K4OAH
Atlanta

Drake C-Line Service Manual
<http://www.k4oah.com>



hbrnut at earthlink.net wrote:

>Garey,
>
>I wouldn't rule out the possibilty that they had more than one supplier. That would explain the difference in our results. It's been a long time since I used them, but I THINK I had decided at the time that they were manufacured by G.E.
>
>Darrell
>
>  
>
>>Darrell -
>>
>>Interesting...  The International tubes I tried would neutralize with no 
>>problem, but were very hard to drive, particularly on 15 and 10M.  I 
>>attributed it to the considerably different internal lead structure 
>>compared to US made tubes.
>>
>>Some brands require considerably different neutralization capacitances.  
>>I'd just as soon avoid making changes to the transmitter though until it 
>>becomes necessary.  So far "good" brand tubes are still readily available.
>>
>>73, Garey - K4OAH
>>Atlanta
>>
>>
>>hbrnut at earthlink.net wrote:
>>
>>> have never found a brand of tubes that wouldn't work, although it is sometimes necessary to change the value of the fixed capacitor across the neutralizing capacitor. This includes all of the major branded ones as well as some oddball ones. I have used the "International Service Master' tubes successfully.
>>>
>>>73,
>>>Darrell, WA5VGO
>>>      
>>>