[Amps] TenTec Centurion - 422 tuning question

[Jim Thomson]

Date: Thu, 23 Dec 2010 15:29:08 -0800
From: Jim Brown <jim at audiosystemsgroup.com>
Subject: Re: [Amps] TenTec Centurion - 422 tuning question

On 12/23/2010 2:53 PM, Alek Petkovic wrote:
> Confusing indeed. I noticed the same thing with the Emtron DX-2SP at
> my club. Turning the knob to the right increases capacitance.

This seems to be the way Ten Tec power amps are set up.  My Titans, 
vintage 1980, are also set up that way.

n 12/23/2010 2:46 PM, Gudguyham at aol.com wrote:
> I am still confused about 10 being full capacity.  The dial could have
> been put on wrong.

So take the cover off and look at it!  That's what I did.  End of 
confusion. :)

It's also quite easy to change, simply by taking the knob off and 
re-seating to zero at max capacity. Now capacitance will be minimum at 10.

##  Correct.  I have seen this same error on a few HB amps as well.
With the load at '0'... the load cap should be fully meshed. And
min C  when at '10'.  Turning the load CW  should  Decrease C. 
When you increase the loading you are decreasing the load C. 

## I worked on a buddy's centurion years ago [one bad tube had a grid to
cathode short, which caused both tubes to run bright orange.]   When the
centurion 1st came out... it sucked normal idle current...on RX !!   They all did that.
Apparently ten tec didn't figure out that the tubes are supposed to be cut off on RX.  

## I also noticed on my buddy's  centurion, that the loading control is real  sluggish..
but only on 160m [dummy load].  If you look at  [ and measure] the  tune, load  and
coil  for 160m, it's obvious that they run it at a real low loaded Q on 160m.    Being a 
simple PI net, they used a smaller than normal tune cap... and  bigger than normal coil.
That way they didn't have to pad the tune cap... yet it had a low enough min C to work on 10m...barely. 
Having said that, I have noticed this same sluggishness   on HB amps..again,only on 160m..
and that's with a normal Q, or even with the loaded Q  a  tiny bit on the higher side of normal. 
By sluggish, I mean the load control tunes real broad  vs the external wattmeter. 

Jim   VE7RF


It's also important to realize that a pi-network is an impedance 
matching network.  So changing the value of the capacitors changes the 
match between the output impedance of the tubes and the connected 
transmission line.

73, Jim K9YC