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Reviews Categories | Amplifiers: RF Power - HF & HF+6M | Ten-Tec Centaur Help

Reviews Summary for Ten-Tec Centaur
Ten-Tec Centaur Reviews: 29 Average rating: 4.8/5 MSRP: $749
Description: Full QSK 600W HF linear amplifier
Product is in production.
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K4AAZ Rating: 5/5 Sep 13, 2013 08:50 Send this review to a friend
great amp ,rarely seen for sale  Time owned: 3 to 6 months
Local ham had one for sale,pristine condition,he had sent it to Ten Tec for check up..I replaced 811 tubes with 572B ,replaced fan with quieter 40 to 50 watts from transceiver get 400 to 500 watts out on 110 ,tunes easy,nice small amp....
N1DZ Rating: 5/5 Nov 9, 2010 19:20 Send this review to a friend
Great amp  Time owned: more than 12 months
This is an update of a previous review. I am using this amp now for over 12 years. Modified the fan and made it nearly silent with a heavy duty serie resistor. Using 572b tubes. Recently recapped and added a Harbach soft start. Tuning is super smooth and output is 500-600 Watts. Recently I had a problem with a hanging input relais. Called Ten-Tec and within 5 days I had a replacement relais for less than $12.00. Mind you this amp has not been in production for many years. What a service!
This is a great 600 Watts amp, solidly built with great factory support. Unfortunately Ten-Tec does not make this amp anymore.
AF5U Rating: 5/5 Sep 18, 2010 08:26 Send this review to a friend
Modified - Now Almost Perfect  Time owned: more than 12 months
I bought this amplifier as a walk-in at the factory in 2001. It was preowned. Went through several final sets of tubes both 811As and 572Bs. Blew out components on the circuit boards. One day I found and solved the problems. Also did several modifications to solve the jump off the bench when you turn it on issue (current surge), the fan (120VAC) noise (now use 24VDC fan on 12VDC), and the LOAD capacitor plate shorting. Now the thing could not be sweeter. Love the QSK in CW and ruggedness of the 811As - don't waste your money on 572Bs. Yes, you "might" get a few more watts but at what cost per watt? Need a 100 bucks in your pocket - put in 811As! The guy you QSO will never till the difference on his s-meter.
AB3EN Rating: 5/5 Jul 16, 2010 03:40 Send this review to a friend
Great used buy!  Time owned: more than 12 months
I picked up this amp about 1 year ago. The previous owner had new 811's installed and one blew as I started it up. I replaced the 811's with 572B's and got new resistors for the plate connector board. I get a solid 700+ watts peak out of the amp with 75 watts drive, as indicated on the LP-100 wattmeter. It is a nice addition to my K3 and really helps in the morning with the rotten apples (7.238). If you can find one buy it, if run in to problems Ten Tec is there to help you. Both Ten Tec and Elecraft have the best customer service I have seen. Both make great products!
W4HT Rating: 5/5 May 1, 2010 15:00 Send this review to a friend
Top Quality Top Drawer Medium Power HF Amp  Time owned: more than 12 months
I have owned the Ten Tec Centaur now for about 3 years and it been flawless. No bangs, pops, or any anomalies. It is easy to tune and still produces 500 clean watts on CW and about 600 watts PEP on SSB. By the way, I am still using the original Svetlana 811A tubes that came with the amp from the factory. I only use the it in about a thrid of my QSO's but it's great when needed. I do agree with the comment regarding the wimpy switches. I haven't had to replace any of them yet but it does not appear that diffucult to get at them. All in all a quality medium power amp with inexpensive 811A tubes, a well written owners manual, and yes Ten Tec is still in business and will answer questions reagrding this product(or anytning else they have produced over the years). If you can find a good specimen buy it and enjoy!
W8UDX Rating: 5/5 Dec 21, 2009 18:53 Send this review to a friend
A great old friend  Time owned: more than 12 months
I was thinking tonight that every time one of my three very high-end amplifiers thumps and ceases to produce RF, I always take the cover off my Centaur, replace the big, non-functioning brute, and I am back up and running. I think that just about says it all. Thank you old friend.
WD9CMD Rating: 5/5 Apr 18, 2008 14:51 Send this review to a friend
Centaur is still perking along  Time owned: more than 12 months
After several years on the same set of chinese 572b tubes, I must commend the TT folks for a rock solid amp. The only issue with the amp is the wimpy switches. I've replaced one last year that went bad and then..... now the Ig/FWD is bad. Bummer. Why, because they are an absolute b.... to change out. Very hard to access, and way too small for what they do. Oh well, if thats the only thing wrong, so be it. It still works like a top. Quiet with the pabst fan and excellent out put with the 572b's. Also loads up great on 17m on the 15m bandswich. I can push this amp to 800w out on 40 most any time without excess heating apparent. I'd only try this on SSB (and not for ragchew) as if you did this on another mode, excess heating may fry some components. Anything more than say 650 out is a waste anyway. If you need more go to a bigger amp !! But I find this amp to be perfectually adequate for the majority of ham operating.
Good luck, David wd9cmd
NB7I Rating: 5/5 Apr 15, 2008 13:59 Send this review to a friend
Fine QSK Amp  Time owned: more than 12 months
I bought one years ago, and never had any trouble with it. It put out 600 watts with no trouble, but ran it at 500w. Not sure why there were so many who couldn't get that out of it. Using it with a QSK radio showed the big advantage over similiar amps.
I sold it only because I didn't need an amp anymore.
The high drive requirement may be due to the simple input circuit - a 50 ohm resistor.
KR9D Rating: 5/5 Apr 15, 2008 13:36 Send this review to a friend
A significant improvement on the AL-811 for only a few more $  Time owned: 0 to 3 months
I recently purchased a used Centaur for my primary operating position, so I could move my AL-811 (which has been trouble-prone) to a secondary operating position.

The seller of the used Centaur I bought warned me that the QSK/PTT switch had a bent handle, and I foolishly tried to straighten it. Of course, it broke, and I replaced that and the bypass switch with mini-toggle DPDT switches from Radio Shack. They look the same as the (admittedly low cost) originals and they work. I may order something a bit nicer from Mouser in the fullness of time.

Working on the Centaur is a pleasure. It comes part easily, unlike the AL-811 (which I also own), and the panels can be removed without unsoldering anything. Just like the Omni V. A lot of disassembly is required to remove the front panel, but it's all obvious and easy to reassemble, especially compared to the AL-811.

Yes, the fan is noisy. But I never felt much warmth coming off those Chinese 811's, even after heating up my dummy load quite a bit. And I barely heard it at all when wearing headphones, as I routinely do.

The Centaur has a forward power meter, which the manual claims is only calibrated in the 400-600 watt range. I doubt that it is calibrated at all. I was reading 600+ watts consistently on 80-15 meters and 500 on 10 meters into a dummy load, with grid current well below 125 ma and plate currents well below 500 ma even key down. I measure output using an Ameritron AWM-30 true peak-reading power meter, which also allows me to tune up using CW dits instead of key down.

Previous reviews and statements in the various Ten Tec archives reveal many who were unable to get the full rated power out of the Centaur. I think I know why. The power meter just plain reads low. When putting out 600 watts key down (as measured by the AWM-30), I was also seeing over 600 watts on my Ten Tec Model 229 tuner's power meter, but only a little over 400 watts on the Centaur's power meter. I wonder if those who didn't think they were getting full power really were.

The Centaur tunes quickly and easily compared to the AL-811, and runs at rated power with lower grid and plate currents.

Something I can't explain (based on the usual descriptions of 811's in grounded-grid AB configuration), but that agrees with the ARRL review, is that it reaches rated power at an exciter power of 80-90 watts, instead of 55-60 watts as with the AL-811. This is a good thing, in that it largely prevents an overdrive-based Big Mistake. Tuning is easy: Set RF Power on the transceiver to the middle of the dial, send a string of dits, tune the amp for maximum power, turn the RF power up to about 9 on a scale of 10, and tune for maximum power on another string of dits. Keep an eye on grid current, keeping it below 125 ma. Plate current should be below 450 or 500 ma, but may be a bit higher during tuning. Reduce drive if desired. The Centaur tunes in half the time of an AL-811, at least with my hands on the controls.

The circuit design seems safer and a stock AL-811. For example, the bleeder resistors are in pairs and paralleled. Ditto for the parasitic suppression resistors. The design resists a serious fault from a failed resistor. The execution is considerably more robust. The voltage rating of the power-supply caps is 2200 volts against a high-voltage supply of 1800 volts. On the AL-811, the caps are rated to 1800 volts, which depends on everything being perfectly matched to keep one of the caps from experiencing a bit higher voltage than the rating. The design includes fault protections such as prevention of hot-switching, which the AL-811 does not have.

The transformer in the Centaur is substantially beefier (and heavier) than the transformer in the AL-811.

I could not find a way to overdrive the tubes, except I suppose by running it at full exciter power in an untuned state. The notion of putting 572b tubes in this amp just for improved forgiveness seems really unjustifiable. I'm leaving the Chinese 811's in it until I have a reason not to.

And then there's the QSK. I am not a CW operator, but I could easily hear the band between the dits at 30 or 40 WPM. It works so well it makes me want to work on those CW skills. The Centaur provides a standard keying loop with the option of a direct PTT input. Using a transceiver with a keying loop, the setup is easy and works in all modes. QSK is possible without such a transceiver, however, by hooking the key up to the Key In on the amp and running the Key Out to the PTT input on the transceiver. For phone, supplement this arrangement with a line from the amp control relay output of the transceiver to the PTT input, and use the PTT/QSK switch on the amp to switch between the two modes.

The amp provides ALC, but with the high input drive requirement I observed, I don't see much need for it. In fact, if the transceiver drive is set to provide 600 watts (properly measured) of amp output key down, then ALC is not needed.

Ten Tec's manual is typical of Ten Tec: Informative and complete, with a schematic, board layout, and operating description of every board.
G0BYH Rating: 5/5 Feb 11, 2008 02:42 Send this review to a friend
No regrets  Time owned: more than 12 months
Bought this amplifier approx' 7 years ago and apart from one 811A tube failure (My fault) and one scale lamp blowing it's never given any problems. Upgraded it to 572B's just to overcome some of those "Tune Up" mistakes HI, and it loafs along at 400w with just 50w of drive from a TenTec ORION, mainly gets used on RTTY (200w) and SSB.
If you are looking for a mid power range amplifier and can find one second hand would definitely recommend this one.
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