[GreenKeys] tube?

[Richard Knoppow]

----- Original Message ----- 
From: "Duncan Brown" <duncanancy at earthlink.net>
To: <greenkeys at mailman.qth.net>
Sent: Sunday, January 06, 2013 3:29 PM
Subject: Re: [GreenKeys] tube?


> Tim,
>
> Yes, the tube is a 25L6GT, designed to work with military 
> 24-28VDC supplies.
>
> The first time I put power to our TT-30 (military, 26VDC, 
> version of the M31), the motor ran fine, but then it 
> started to slow down. Thinking something was binding or 
> there was a bad bearing, I shut the power off quickly. 
> After checking for anything overheating, I tried it again 
> and got the same result: motor slowed down after a few 
> seconds, but then maintained the new speed.  Then I 
> realized that the filament had to warm up before it would 
> start regulating!
>
> Duncan,
> K2OEQ
>

     The 25L6GT is a high-voltage heater tube meant for 
AC/DC radios with series string heaters. There is a more 
common 50 volt heater version, the 50L6 which is found in a 
great many AA-5 type radios.  Its a beam power tetrode used 
as the audio output tube but could undoubtedly be adapted to 
regulator applications.


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