Centaur 411 Amp

Chuck (Jack) Hawley c-hawley@uiuc.edu
Sat, 14 Dec 1996 09:20:40 -0600

Ten-Tec Inc. wrote:
> Hello from Ten-Tec !
> At 11:06 PM 12/12/96 -0500, you wrote:
> >Hello. I am the proud owner of a brand new Centaur.  It is very VERY nice amp
> >- beautiful QSK on CW!   It is a good size and looks nice sitting next to my
> >rig.  I've received good signal reports on SSB, AM, and even FM on 10 m.
> >
> >I have one question though ...
> >
> >When I drive the amp in CW mode with 150 ma grid current and around 500 ma of
> >plate current, the wattmeter flys off the scale when you switch to "Forward".
> > To get the forward down to 600 watts, you have to cut the drive way back to
> >around 75 ma grid, 250 ma plate.  I'm only driving the amp with 70 watts or
> >so from my transceiver.
> >
> >Is my meter calibration off?  Anyone else out there experience this?  Any
> >thoughts?
> Yes, the wattmeter is out of calibration.  If you don't have another
> wattmeter to calibrate it against, tune it up for max. output on 20 or 40
> meters into a dummy
> load (you should be putting in a full 100 watts after tune-up).  The adjustment
> screw (small phillips head) is accessible from behind the amp.  It's a small
> hole
> just below and left of the serial number.

Two things......seems like it would be good to have a better calibration
procedure during production since it didn't get misadjusted by itself.
The other thing is the test report in CQ that went into great detail on
how to avoid arcing of the tune capacitor in humid weather. I don't
think the tune capacitor should be so easy to arc over. Isn't the
voltage rating of the cap too low for the application?
I am very sympathetic to TT and suffer with a few design bugs in the TT
auto antenna tuner because I like the thing overall. And, one of these
days I'm going to buy an Omni VI so that I have something to work on
that is otherwise a better performer than mediocre rigs that work
perfectly. But, I just don't think that the product review should lay
the responsibility of an inadequate design on the guy who just paid for
a brand new commercial amplifier. It may come down to the owner having
to deal with the problem himself just as I have to with the brain
damaged auto tuner, but not right out of the gate as Doug DeMaw did in
his "review".
So there....73.

Chuck, KE9UW

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