Phil, Art and all;
The Centurion I have was purchased new by me from Tentec in March of '96.
It has the original tubes, transformers, capacitors, diodes and such. I
find it to be a very reliable amp and a work horse. Consistently, it
delivers some total 1400 watts output as measured on 2 different watt
meters. Now, although it is rated at 1300 watts output SSB, do remember
that the 1400 watts I measure does include about 100 watts of drive power
from the transceiver. That power also appears as part of the output.
Transformer wise, I find it to be quite solid. Yes, the voltage per the
manual shows 3100 to 2600 and is a "no load" to "full load" condition. No
load condition will never exist except during stand-by as the tubes are at
full cut-off. Full load condition will exist on TUNE only with carrier
which will net about 2600 volts at 0.8A of plate current for 2080 watts
input developing an output of 1300 watts {amp power less drive power} for
62.5% efficiency.
For SSB, the duty cycle being very short, the Keyed voltage should be about
2900 volts {tubes at idle current of 100 ma} and with voice the voltage
drops another 100 to 200 volts. This is the result of the capacitance in
the power supply holding the voltage very solid. On a 230 VAC source, my
amp is running 2900 this morning, KEYED {no signal} it drops about 100 volts
to 2800, and with voice I can see about another 100 volt drop. This is a
regulation of 93.1%. Very acceptable in my opinion and experience.
I would say that replacement of the transformer is totally un-necessary
unless one has failed. As to going to higher voltage, the 3-500Z is rated
at 4000 volts maximum and 3000 volts typical. Based on my measurement,
observation and results, higher voltage is not necessary. In conclusion,
this is not a "legal limit" amp but with my results the station is capable
of 1400 watts as opposed to the 1500 watts legal limit.
Regarding duty cycle, I frequently run AM at 250 watts of carrier output
with no problems. I also run full QSK CW at 750 watts output and experience
excellent results. For a desk top amp, the Centurion is a very good buy.
The input and drive impedance nets a 1.5 : 1 SWR on all bands and
frequencies except 160M where it will be 2.0 :1 at the band extremes. Most
transceivers tolerate these value very successfully and thus provide
adequate drive to the amp.
I'd say the biggest fault that might exist with the Centurion is largely
improper operation. Having repaired a few of these for other folks, these
faults are likely the result of poor antenna load conditions, either wrong
antenna for frequency, or antenna with suddenly high SWR either from a
shorted line or open circuit. Changing the band switch while tuning is
always one that produces a failure mode, hot switching between RX/TX due to
improper transceiver interface means, and of course lightning strikes where
little if anything survives.
All in all, the Centurion is a well designed amp and a day-in and day-out
work horse.
73
Bob, K4TAX
----- Original Message -----
From: <atrampler@att.net>
To: "Discussion of Ten-Tec Equipment" <tentec@contesting.com>
Sent: Saturday, January 17, 2009 4:37 AM
Subject: Re: [TenTec] Centurion question
Phil,
You can read about people replacing the transformer in the Centurion
(there
was something about TT losing the guy who made their transformers/getting
them from somebody else) but I think the issue you are talking about is
one
of design, not of robustness.
I pull a KW (and a bit more if I wanted to) easily from the unit. If the
RF
deck were designed for more power, then yes, running a higher plate
voltate
would or could make sense to increase the power out. Some Henry's ran 4KV
key up, and produced about 2KW out from a pair of 3-500Zs.
In case you really want to, look here:
http://hamradiomarket.com/articles/Ten%20Tec%20Centurion.htm
The neat thing about the Centurion is that the plate transformer is just
that...the plate transformer, not supplying filament or other voltages.
So
this fellow modified his by building an external 4KV supply. He claims
the
RF deck is nice and robust and good for this and therefore the unit
becomes
a legal limit amp (he was pulling 1700 watts out of it), but I don't feel
comfortable with that. That's just me...I'm not an engineer.
So I hope this short answer was worth it. One nice thing about the
modification he did is that the HV PS now sits on the floor away from the
amp which is made considerably lighter.
73,
Art, K0RO
----- Original Message -----
From: "Phil Sussman" <psussman@pactor.com>
To: "Discussion of Ten-Tec Equipment" <tentec@contesting.com>
Sent: Saturday, January 17, 2009 3:10 AM
Subject: [TenTec] Centurion question
Greetings,
I am considering the purchase of a Centurion HF amp. After reviewing the
specs,
I'm wondering about the 3100vdc supply dropping to 2600vdc under 'full'
load.
Is the power supply heavy enough? My past experience with dual 3x500Z's
has
plate voltage holding at 2900vdc to 3000vdc typically under full load
conditions.
Comments certainly welcome.
Thanks,
de Phil - N8PS
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