[TenTec] Centurion mod

[Carter Grabarczyk]

Rob Atkinson, K5UJ wrote:
> I'm working from memory--I'm sure someone else knows exactly what this 
> is or you can find it in the reflector archive--the Centurion originally 
> was biased so the 3-500s were operating @ around one or two hundred 
> mills when not transmitting. the mod shut them down completely between 
> key closure.  Do I have this right?  someone help me out here--


I guess it depends on the vintage. Mine came from the factory with the 
board already installed. It was a "Revision B" board. Very early 
Centurions may not have had it at all. The rev B board blew up on me a 
couple of times and I got tired of fixing it so I finally bought a new 
Rev C board from TT and it has worked flawlessly for the last several years.

The only other mod I put in was a wire wound resistor to lower the 
filament voltage. It is probably a quirk with my filament transformer, 
but the filament voltage was quite high even with "nominal" primary 
voltage. As the cost of 3-500s is steadily climbing, the point of the 
exercise was to extend tube life. I guess the real fix would have been 
to remove a turn or two off the secondary of the fil xfmr, but I wasn't 
retired then and didn't have time to do it that way...

73/Carter/K8VT