[Amps] Ten-Tec Centurion Design Flaw?

[Rob Atkinson]

I am the one who may have written about the Centurion caps previously.
 I have modified my Centurion by removing the stock caps and putting
in HEC doorknobs.  I kept the 40 and 80 m. arrangement and kept the
HECs close to the stock values because the amp tuned and loaded okay
on those bands.  I thought load tuning on 160 needed help so I added a
doorknob on that band with the lug on the bandswitch that is otherwise
unused on 160.  But my main reason for the doorknobs was because I use
the amp on AM which it was not designed for, and the duty cycle and
current on 160 seemed to tax the stock caps.  If your customer only
intends to use his Centurion for CW and SSB those disc caps may be
okay.  I checked them out and they are good RF class 1 disc caps, just
not high current low frequency caps.

Why did they do it?  Because Ten Tec like most for-profit companies,
employs engineers who are paid to save the company money.

73

Rob
K5UJ

On Sun, Dec 2, 2012 at 11:50 PM, Jim W7RY <jimw7ry at gmail.com> wrote:
> I’m working on a Ten-Tec Centurion for a customer. I noticed that the load capacitor padders are not hooked to the band switch correctly.  The schematic depicts the way they are actually wired in an actual unit. Which is....
>
> The load cap by itself is 800 pF.  They add C13 which is 330 pF on 40 meters, an additional C19 which is 430 pF on 80 meters, and NO additional loading on 160!  This is a standard PI network tank
> circuit. Not Pi-L.  I would think the load padders would be needed on 80 AND 160. Not on 40.
>
> I know there was some discussion here about using doorknobs instead of Ten-Tec installed 2KV disks. When I get the amp back together after the band-switch repair, I’ll see if the load padders drift as
> reported. I think I’ll move the padders before I install the tank assembly back into the amp.
>
> Does anyone have any insight why Ten-Tec did this? Is there enough loading capacitance in a stock Centurion for 160 meters?
>
> BTW The older SB-220 has an 540 PF load cap in it, the newer SB-220 and the HL-2200 have a 840 pF load cap. Heath adds a 500 pF mica on 80 meters.
>
> 73
> Jim W7RY
>
>
>
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