[Amps] Ten-Tec Centurion

[Michael Tope]

Tom,

One interesting thing to try would be to put a shorting plug on the
Centurion relay control input so that the T/R relay stays closed all
the time and then check to see if any arcing occurs on leading
characters from the exciter. That experiment would control for
hot switching of the T/R relay. For convenience, you could use a
footswitch on the amp control line and close it before you start
sending.

73 de Mike, W4EF..........................

----- Original Message -----
From: "Georgens, Tom" <tom.georgens at engenio.com>
To: <amps at contesting.com>
Sent: Wednesday, November 10, 2004 9:08 PM
Subject: RE: [Amps] Ten-Tec Centurion


> Thanks to all respondents for the thoughts.
>
> A few comments.
>
> 1.  The fact that it does not happen with the other amps does work against
> my theory.  I should note that the other amps are not the same (AL1200,
> TL922, AL80A).  That said, I don't think it disqualifies the theory.  The
> AL1200 can probably absorb the spike.  The TL922A relay is so slow, the
> spike may pass before the relay closes.  No guess on the AL80A.
>
> 2.  The RFsense in the Centurion is in support of QSK.  It is not intended
> to work the way I inadvertently used it.  It is true that it necessitates
> hot switching of the relay.  I do believe that it supports the theory of
an
> overshoot transient.  Oddly, the despite the hot switching, the
transceiver
> does not fold back.  Conversely, the TL922 is so slow that it does cause
> foldback.  Even if the RFsense makes the problem go away, this is not how
I
> wish to operate the amp.  I still would want to understand root cause.
>
> 3.  The padder cap transient response suggestion is a good one.  However,
> when not arcing, the amp works exactly as expected with the settings where
> the manual suggests they should be. The padder caps are also both used on
80
> as well.
>
> 4.  I do not think the antenna is much of a factor.  It is a halfwave
> inverted V at 90 feet.  Admittedly, it is not a pure resistive 50 ohms at
> all frequencies but it should be well within the tuning range of the amp.
I
> mention it just so that you all know it is nothing exotic or dramatically
> shortened.  I believe it to be free of intermittent connections.
>
> 5.  K2VCO's suggestion on the carrier level is something I will try.  I
may
> be causing this myself.
>
> 6.  Could advancing the load control slightly help out?
>
> 7.  I was also going to try and see if the problem still happened with the
> radio autotuner on in case it impacted any potential spike.
>
> 8.  Ten Tec suggested that the variable cap is probably pitted, causing
the
> arc.  I do not think this is the problem as the arc is not always in the
> same place.
>
> 73, Tom
>
> -----Original Message-----
> From: amps-bounces at contesting.com [mailto:amps-bounces at contesting.com]On
> Behalf Of Georgens, Tom
> Sent: Wednesday, November 10, 2004 3:16 PM
> To: 'amps at contesting.com'
> Subject: [Amps] Ten-Tec Centurion
>
>
>
> I have a Centurion at my contest station in Barbados that works flawlessly
> on 10-80 but will arc on 160.  It is tuned into a resonant antenna with a
> reasonable SWR.
>
> On 160, the amp will occasionally arc immediately on key down.  If it does
> not arc immediately, it will not arc if the key is held down.  Also, when
it
> does not arc, it tunes smoothly and at the predicted settings.  All of the
> arcing is in the Tune cap and is not always in the same place.
>
> My theory is that there may be power overshoot from the TS850 on the
leading
> edge of the carrier that is causing the arcing.  It is hard to see this on
> the wattmeter and my 3 other amps all work fine.  Does this seem like a
> reasonable theory and is there any way to compensate for this?
>
> On my most recent trip, I performed a flawed experiment.  For convenience,
I
> used a different TS850 to drive the amp and the problem occurred only once
> out of dozens of tries.  I then moved it to the TS850 where I had
previously
> noted the problem.  In this case, I was never able to reproduce the
problem.
> I tried mistuning to some degree but no hint of the problem.  However,
when
> taking the whole thing apart, I noticed that I had never connected the amp
> relay cable.  The amp was using RF sensing to key the relay.
>
> As I said my experiment was flawed but I would like to understand what is
> really happening.
>
> Any suggestions would be greatly appreciated.
>
> 73, Tom W2SC 8P1A
>
> Tom