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Reviews For: Ten-Tec Centaur

Category: Amplifiers: RF Power - HF & HF+6M

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Review Summary For : Ten-Tec Centaur
Reviews: 31MSRP: 749
Description:
Full QSK 600W HF linear amplifier
Product is in production
More Info: http://www.qsl.net/tentec/
# last 180 days Avg. Rating last 180 days Total reviews Avg. overall rating
00314.8
PA0FRI Rating: 2003-07-17
Reliable Time Owned: more than 12 months.
It is unwise to obtain 600W output using the 811A’s and exceding the ratings of the tubes. You have to pay attention during tuning up and reduce the level of a speech processor. I have seen holes burned through 811A plates. Fit three 572B’s and the amp will survive its owner. The 572B’s can tolerate much more abuse and output power. The transformer is a very hefty 1kW type so I added an extra tuned input circuit. The output power is increased to 750-800W.
The noisy fan is replaced with a 70.000h 28VDC Papst fan of the same size and slowed to whisper quiet with internal 14VDC. With a thermal relay and a voltage quadrupler the fan automatically switch to 28VDC.
KQ4KK Rating: 2003-07-02
A Good amp Time Owned: more than 12 months.
I had one for 3 years. Worked good. Blown fuses were the only problem. The 811 replacement issue made me sell it. Noisy fan!
W9KX Rating: 2002-12-28
Good QSK medium power amplifier. Time Owned: more than 12 months.
I purchased my Centaur from Ten-Tec in the fall of 1996 and it is still in use today - some six years later. The amplifier is used mainly on CW from 80 to 10 meters. Since an antenna tuner is always used, the output SWR of the amplifier is always 1:1. It is driven by an Omni 6 (plus).

When I purchased the amplifier I knew that it was impossible to obtain 600 watts output power (600 watts 80-15, and 500 watts 160 & 10) using three 811As without exceeding the "absolute maximum ratings" for the 811As. More on this issue later.

First, I found I couldn't rely on the accuracy of the Centaur output wattmeter. (I use an external wattmeter that was calibrated against a Bird.)

Second, I had to replace the original 811As after three years of use. Again, I found that in order to obtain rated output, i.e. 600-500 watts, the tubes were at times pushed well beyond their ratings!

I replaced the 811As with three matched "RF PARTS/SVETLANA 572B"! (Note: 572B is a direct drop-in replacement for an 811A.) Using 572B resulted in the tubes LOAFING along at 600 watts - and also resulted in REDUCED drive requirements on the upper bands and with a REDUCTION in plate current!

Other than the internal wattmeter accuracy and replacing the tubes, the amplifier has operated FLAWLESSLY.

Dean, W9KX
KY6R Rating: 2002-12-21
A good value amplifier Time Owned: 0 to 3 months.
I was able to get one in "like new / mint" condition, with very low mileage.

It is as large as a desktop PC, and the fan is as noisy as a desktop PC's fan. I have mine on a very sturdy table, and its rubber legs seem to absorb any rattles. The fan keeps the tubes very cool - I see no problems there. But I only use the amp for short DX pileup busts, and only when I absolutely need it. So I am a light QRO user . . I probably wouldn't use it to ragchew on 75/80 or 40 . . .

I read the reviews here before I bought - so I have been forwarned about the wimpy switches. Same problem as my rotator control box - it has a wimpy set of switches - so I buy parts ahead of time!

If you can get one for $500 or less in mint condition and with the 10/12 meter board installed - you get a half gallon with QSK that is very well built for the $$$. I also called Ten Tec and they were willing to answer my questions - and promptly.

This is the third piece of Ten Tec gear I own - I think their value and quality and support is winning me over.
W0DC Rating: 2001-07-14
Excellent Value Time Owned: more than 12 months.
The Centaur is an excellent value for a mid-power amplifier with coverage of 160 to 10 meters and full-QSK. Very unfortunate that tube availability problems caused Ten-Tec to halt production. If you run across a clean one, buy it!
K5VOA Rating: 2001-02-16
Great Amp - Especially After Quieting Fan Time Owned: more than 12 months.
I have had the Centaur about a year and found it to be reliable, easy to use, but with two problems: poorly engineered tube cooling and cheap toggle switches. I had to replace a failed switch after a few hours of use. Not enough problem for a warranty claim, but an annoyance. The fan noise is ridiculous! Obviously the cooling system was an afterthought or Ten-Tec had a cheap supplier of 100 CFM fans. I compared the Collins 30L1 with it's four 811As packed tight in a cabinet with small perforation and tiny hi-fi style fan. I am familiar with the 30L1 in military application and can attest to its 811A life & reliability. I replaced the Centaur fan with a 12VDC fan of the same size and slowed it to whisper quiet with a 100 ohm 5 watt wirewound pot adjusted to about 60 ohms. The new fan is externally powered (although 14VDC is available inside). I am now very pleased and I am sure the 811As will last a long time even though they run a bit warmer. There is still plenty of air moving and lots of convection air space. Even at a fan speed quieter than my Icom rig, the Centaur is cooler than the 30L1 reference standard. My Centaur is now up to my expectations.
K5ROV Rating: 2000-11-12
Great, but... Time Owned: more than 12 months.
I find the amplifier does everthing TenTec says it will. I get at least 600 watts, the signal is clean, and it is well worth the money. I have had it for over two years and it is reliable and a pleasure to use. Yes, the tuning is a bit critical, but not really a problem.

But it suffers from one problem. The miniature switches used are cheap and do not last. But that is only a small part of that problem. When a switch goes out, you will never forget the experience trying to change it. The front panel must come off, and part of the inner bulkhead. I called the factory when mine went out and they recommended I return the amplifier because of the difficulty in changing the switches. But I knew the others would soon go out and I did not want to ship it every time I had such a problem.

Those switches will go out; count on it! Changing them is a nightmare. Not only is it a major overhaul to change the switch, but getting a soldering iron in the tight area is almost impossible. If one more goes out, I am going to drill out the holes and put in large, well made switches. TenTec should have done that to begin with.

In defense of TenTec, they did send me the needed switch for free, even though the Centaur was out of warranty. And they even sent me a spare.

A great amplifier for the price, but get ready for a nightmare when the switches go out!
W9WIS Rating: 2000-05-07
Centaur is a winner in the 600 watt amp class ! Time Owned: more than 12 months.
I've had my Centaur for about two years and have never even had it "burp". It can easily achieve it's rated 600 watts out and I have had no RF problems associated with it. I run mine off a dedicated 120 volt line with no problem. True.... some find the 100 cfm fan noise annoying but it hasn't hampered my operating or my opinion of this great little amp. The 811A's have been discontinued by Svetlana, the mfgr of the tubes in the Centaur, and rather then use what they felt were inferior tubes Ten-Tec stopped making the Centaur. Too bad..... now there is only one other choice for an entry level 600 watt tube amp.... and they are no Ten-Tec. The amp's tuning is very smooth.... like mentioned previously it...like all amps.... is a bit more touchy on the high bands but this sure isn't a problem. The fit and finish are both excellent on mine...... I don't know what they could have done to make this amp better ....except lower the cfm of the fan to lower the noise level.... but I think they opted for prolonged tube life instead of a quiet fan...... now that Svetlana is out of the 811A business thats fine with me !
W0VC Rating: 2000-03-07
Nice little amp, but awfully noisy Time Owned: unknown months.
The Centaur receives four stars from me because of its basic "bullet-proof" design and the legendary Ten-Tec QSK. It suffers from the usual Ten-Tec fit and finish problems that diminish the equipment's value. This is nice little amp, but the thing is awfully noisy due to the 100 cfm fan. It rattles the tube elements and vibrates the operating desk. Some owners are changing out the fan to rid themselves of the problem. The Centaur feels beefy, the transformer is very hefty, the tuning knobs very smooth, but the tuning gets somewhat touchy as IG and IP maximums approach. My rig is an Omni VI+ and this 'lil amp was made for it. The QSK is incredible, and in my book this offsets some of the negatives. I have to fess-up to being very picky and keep hoping that Ten-Tec will become the Drake of the 21st century. They have along way to go in fit and finish and value competition with the Japanese manufacturers. Now that Ten-Tec has discontinued the Centaur, the prices will come down, and anyone needing a basic amp, willing to change out the blower, will find a good bargin indeed. This little baby cooks, especially on CW.
AC5AA Rating: 1999-11-11
Excellent, sturdy, but a bit noisy Time Owned: unknown months.
I owned an Centaur for just over a year and it did a wonderful job for me. Never a problem with the three 811A's, and no RF problems in the shack. Fan noise is not bad if you use headphones, which I do. An excellent amp for the $$$.