Centaur 411

[Billy W. Cox]

Guys and Gals ...

I (while my xYL/YLs were out feeding the starving merchants of
Gatlinburg/Pigeon Forge) visited the TenTec plant Friday and saw
first hand their new amplifer. And used it ...

It's a sweet unit. NO, it's not an ETO Alpha 87-a, but then again
it does not cost what that unit does either (say just 1/8 $ or so ?)

I had no problems tuning it up into a TH7DX using a Omni VI
and obtained 600 watts output on 20m CW ...

No arcs, snaps, pops, or crackels. Total tuneup time was 
less than 15 seconds from moving the amp from another band.
Used low drive, peaked the amp, raised the drive abit, peaked
the amp again quickly, and then increased the drive to bring
the amps' output to 600 watts and repeaked the controls again.
Each step took about 5 seconds for a total of 15 seconds or so.

The amp remained on during my entire visit, at no time was
the blower noise what I would call "loud" or "excessive". It
is in fact quieter than either of my older AL-1200 amps that I own.
Other hams visited the TT station and no one seemed to be bothered
by the amp being on while talking to each other at normal levels.

All things considered it's a good compact unit. Years ago when I
was a young ham (age 14) we built up a 4x811a amp, that thing
lasted forever ! What Tentec has provided in the Centaur is
what we tried to build, but could not find all the parts back
then. QSK and 160m were just not to be found on amps back then.
Both are stock on the Centaur ! Likewise on the amp's tuned input
which most rigs of today MUST have to deliver full output ...

After reading some of the postings on here, and actually
having used the Centaur, here's a few comments to consider.

1. For alot of folks this may be your 1st amp, CONGRATS, you
   made a good choice. But, understand that "amps" are ALOT
   different than your (and my) solid state rigs. Many amps
   tend to "fuss" (read arc, spit, hum) when things are not
   just perfect. Ask a Heathkit SB220 owner about that, or
   again, MOST of the other commercial amps out there today.
   Or ask a ETO 87-a owner about how often the amp "faults"
   off line because the load is not "perfect" ...

2. Tuning up any amp into a 50 ohm dummy load for maximum
   output AND THEN switching to the antenna you use, WILL
   require retuning the Centaur or ANY amp for that matter !
   The odds of your (or my) antenna looking like a "perfect
   50 ohm load" is very low. The closer to a true 50 ohm
   match that your antenna is, the closer the settings will
   be to the same as you used on the 50 ohm dummy load. 

3. I did not read the manual for the Centaur to see if they
   suggest a specific length of coax for connecting the amp
   and the xcvr you are using it with. If you seem to be
   having problems with the rig/amp and input SWR, try a longer
   or shorter length. That's an old trick from years past. I
   used it with my TT Omni C to drive a Dentron amp that did
   not have a tuned input, seems like a 6' piece of RG-213 was the
   magic length at that time. SWR is not always what it appears,
   for example "2:1 SWR" is that 100 ohms:50 ohms or 25 ohms:50ohms
   or some combination of reactive/inductive values that look like
   "2:1 SWR" ? Keep that in mind before you start adjusting or
   suspecting the tuned input of the amp. It may be ok ... If
   not contact the service folks at TT and see what they suggest.

4. Here two tips for long tube life (for any amp):
   A. I tune up using my keyer and a PEP type wattmeter. Using
      the dah or di side, you can quickly adjust the amp's output
      by watching the PEP wattmeter. This saves dead-keying the
      amp and is less QRM over the air.
   B. Using stick'em pads or similar behind the TUNE/LOAD controls,
      mark EXACTLY where YOUR AMP tunes YOUR ANTENNAS for maximum
      output. This makes band changing quick and easy. Switch bands,
      preset the controls, use your keyer and PEP wattmeter to VERY
      quickly make sure everything is on the mark, and you are there !
      Actually you can peak 'on the go' using the wattmeter if the
      presets are close, as they should be !

Well ... There's my 2 cents to you for FREE ... Happy Holidays !

BTW, outside of owning a TT 6m tranverter kit that I have had unbuilt
in the box for over a year now, I have no connections with Ten Tec,
not do I own any TT gear at present ... and I'm not an engineer !

73 Bill AA4NU  aa4nu@ix.netcom.com

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