[TenTec] Ten-Tec Centurion 422 , looking for a new Tuning Air Cap

[Bob McGraw]

David:

The buzz is the result of arcing between the plates of the capacitor.  
This typically is the result of the amplifier being too lightly loaded 
resulting in excessive RF voltage in the output network.   Or perhaps 
the SWR is high.   In either case, the voltage in the PA tank was 
excessively high resulting in the arc.   Grounding has nothing to do 
with the issue but all equipment should be bonded to a common point for 
safety reasons.

You can remove the capacitor and disassemble it.  Then using a file, 
carefully file away the rough areas of the affected plates. Then finish 
smoothing them with fine steel wool.   The plates are very soft and can 
be damaged by excessive force.  I suggest laying each plate on a flat 
surface when you are working on it, applying a downward force.  Then 
reassemble and install the capacitor.

I suggest you check your SWR on your antenna system.  Any value of 3:1 
or greater is not suitable for the amplifier.  Address and correct the 
antenna system.    Also when tuning the amplifier be sure to TUNE and 
LOAD the amplifier correctly always adjusting for maximum output.  Then 
reduce drive to the desired operating power, but DO NOT change any 
tuning or loading.

73

Bob, K4TAX

On 10/15/2020 6:32 AM, David Sturm wrote:
> Good morning all,
> I have an excellent condition Centurion that I purchased in 2015 from a Ham
> in Marietta GA
> ( NK9R) and he purchased it in 2001 from another ham and then sent it into
> Ten-Tec for a QSK installation and a new fan.
> The 422 has been working faultlessly for years until last week. I got a
> buzzing sound of 20m. So I stopped using it. I got a similar buzzing sound
> at 40m.
> Nothing has changed, all grounding and bonding in place( I'm in Ecuador and
> have been operating with the same coax, 4" copper flashing for a ground and
> bonding)
> I opened up the cover and found on the stationary plates and the rotor
> plates small pitting and some small melting.
> *What would cause this?*
>
> *I'm looking for an option on cleaning the plates. Can/should this be
> done?( short term)*
> *(Long term)Where can I purchase a Tuning Air Capacitor to replace this
> one? I was trying to find the uf and voltage rating, but I can't seem to
> find it in the manual? Looking in the wrong schematic.*
> Any help would be appreciated.
> Thx
> *David-*
> *HC5DX*
>
> *WB4OZM*
>
>
> *http://carmenlaveranda.com <http://carmenlaveranda.com>*
>
> *I follow the DX CODE of CONDUCT*
>
> [image: http://nfarl.org/picts/nfarlLogoTransparentBackground_medium.gif]
>
> *From Ecuador, at 8,300 (2,500m) feet in Altitude, a 60'(19m) tower is tall
> enough I say!*
> *Love getting QSL cards*
> *Excellent Coffee here, drink some and stay awake for some great DX*
>
> *"It is not the class of license the Amateur holds, but the class of the
> Amateur that holds the license."*
> *David-*
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