[Drake] Drake T-4XB - Found a modification

[Garey Barrell]

Bob -

My guess would be someone who used the transmitter primarily as a driver 
for VHF/UHF transverters.  See if there are two "unmarked" phono jacks 
on the rear panel that interrupt the screen voltage supply to the 
Final.  IF this modification is installed, there would need to be a 
jumper cable between these two jacks to apply screen voltage again, 
otherwise no Idle current will flow.  This function was accomplished by 
switching in the CC-1 or other transverter controller, and was a simple 
way to switch back and forth between HF and V/UHF operation.   Removal 
of the filament voltage was not required, simply removing the screen 
voltage disables the final (as you discovered!) but certainly removing 
the 3 plus amps of filament current would be worthwhile if you did the 
majority of hamming on the V/UHF bands.

73, Garey - K4OAH
Glen Allen, VA

Drake 2-B, 4-B, C-Line & TR-4/C Service Supplement CDs
<www.k4oah.com>



Bob Scott wrote:
> I am working on my Drake T-4XB.  My immediate problem is that I am not 
> getting any bias indication on the front panel meter, nor any output.  
> This is my first time working on this and I noticed that a previous 
> owner put a switch on the back panel that interrupts the 12.6 VAC to 
> the finals.  Why would one do that?
>
> I will let you know what I find with the transmitter, but the purpose 
> of the switch eludes me.  I hope there are no additional modifications 
> to be discovered.
>
> Thanks.
>
> 73, Bob Scott W4ZY
> Woodbridge, VA
>