Hi Michael,
I'm not sure my experience will help you, but here it is:
About 25 years ago I bought a Heathkit SB-220 linear amplifier.
It tuned up just fine on the lower bands, but I had trouble on the higher
bands. The symptom was that I was 'dipping and loading' but instead of the
power output's increasing, it was decreasing - even though my input power
was going up (higher current to the SB-220 PA's).
What I found was that there was a point beyond which I had to increase the
loading control (decreasing the capacitance). From that point on, the
amplifier tuned just fine. On my SB-220, I had to advance the load control
up to 6 (on a 1 to 10 scale) on 10 meters to start being close to proper
tuning. From there on, it was easy.
Best to you - 73
de Mike N4NT@wireco.net
----- Original Message -----
From: Michael Melland <badger@vbe.com>
To: <tentec@contesting.com>
Sent: Tuesday, May 18, 1999 9:57 PM
Subject: [TenTec] Centaur problem ?
>
> I've been having a problem with my "new" used Ten-Tec Centaur amp. I
> can tune it easily on all bands except 15 meters to about rated power.
> On 15 meters about all I can get is 200 watts (freshly calibrated Bird
> 43 and Autek meters). I've followed the tune-up procedure to the letter
> but noticed this problem right away. After about two hours use several
> weeks ago there was a "big bang" and the main fuses blew while tuning up
> on 15 meters and the center tube quit working. I sent the amp back to
> Ten-Tec with a note on the problem and a follow-up phone call. I got
> the amp back yesterday with a new center tube installed and a note
> stating it checked out fine with output to 500 watts on all bands into a
> 50 ohm load. I hooked it up again and still find max out on 15 meters
> of 200 watts....... all other bands are in specifications. I tried
> disconnecting the ground thinking ground loop but same results......
> tried direct into a dummy load , same results too. Checked out my
> exciter (Omni V) which shows 90/100 watts into antenna or dummy. My SWR
> shows under 1.5:1... There does not appear to be excessive swr into
> the amp input and reflected power between amp and rig is low. I'm
> lost..... anyone else have any ideas what could be affecting my 15 meter
> output ?? Bad coax is all I can think of but why only one band ?
>
> 73 de Mike, W9WIS
> --
> Michael Melland, W9WIS
> Winneconne, Wisconsin, USA
> FISTS #4387, 10-10 #69281, QRP-L #1656,
> QRP-ARCI #9875, AK/QRP #478, NorCal
> CW, SSB, and Electronics
> List Administrator: grundig@qth.net
> http://www.qsl.net/w9wis
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