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Author Topic: Ten Tec Centaur 10 Meter mod  (Read 817 times)
N3KQN
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Posts: 2




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« on: November 13, 2017, 01:22:59 PM »

Hi,
Does anyone have the instructions for the 10 meter mod and can e-mail them to me?
Bought the Amp new when it came out and never bought the mod. E-mailed Ten Tec
and no one has any information any more.
Thanks
Rich
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W1QJ
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Posts: 2638




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« Reply #1 on: November 14, 2017, 03:59:51 AM »

Hi Rich, The Centaur is a rather rare amplifier in that in the repair business we don't see too many.  In that class of amplifier the Ameritron 811 series sold the best and few opted to pay extra for the Centaur.  However, I have worked on one and therefore had to study the circuitry.  When I went through the various circuits I realized the rather seldom used input circuit seen on grounded grid amps.  Instead of using the typical "Pi-network" input matching for each individual band, they used a circuit similar to that used on tetrodes.  One Alpha amp used this type of input circuit as well.  That said, the amp had to be designed so that it would not amplify on the 10/11 meter band.  I don't recall off hand if the band switch stops at 15 meters and will not advance to the 10 meter position.  If it doesn't then you will have to have a look at what is stopping it.  Usually a set switch screw or something.  Once that is released the switch will advance.  This is simply an exercise in mechanics.  Electrically I found that the input circuit to the tubes has a 10/11 meter trap.  It is a simple inductor/capacitor network that suppresses that band pass energy and will not allow the amp to amplify in that frequency range.  If you look at the manual it tells you that if you want 10 meters you contact TenTec and they sell you a new filter board.  Apparently the new filter board they sell you passes the 10/11 meter frequencies and allows the amp to amplify on those bands.

The problem is TenTec is out of business and obviously you can't get that 10 meter board.  The original board is called the "15 meter board" and the new board that allows 10 meters is the "10 meter board" as it is referred to.  When I investigated this, I did not have to do the 10 meter enable on the unit I was working on so I did not have to actually pursue this any further, so I stopped there.

However at the time I was curios to know if "in fact" the new 10 meter board was just a gimmick to sell another option.  On other amps which employed the 10 meter "trap" if you will, all one had to do was to bypass or remove the trap and 10 meters would work.  I am wondering if original 15 meter filter (which is actually a 10 meter trap) is removed and bypassed if the amp would then work on all bands without incident. It certainly is worth a try.  You will find out soon enough if it is needed in which case you would have to further investigate.  However if it works you are golden.  At this point now that TenTec is gone and the 10 meter board is probably not available it sure is worth a try.   I hope this helps.
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K1ZJH
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Posts: 3327




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« Reply #2 on: November 14, 2017, 09:04:38 AM »

Rich

One of the better resources for all things Ten Tec is the contesting.com reflector.  You can join and ask if anyone there has the information.

Pete

http://lists.contesting.com/_tentec/2017-11/threads.html
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W1QJ
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« Reply #3 on: November 14, 2017, 01:51:13 PM »

Like I said in the first post the 15 meter board as it is referred to is a "filter" that attenuates all frequencies above 15 meters.  See page
5-8 in the manual.  Board 81550 is that board.  I would simply remove the board or jump it out so that it is out of circuit. The manual is here

http://www.tentec.com/wp-content/uploads/2016/05/Model_411_Centaur_Owner_Manualdc8c.pdf
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N3KQN
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« Reply #4 on: November 15, 2017, 03:46:01 PM »

Thank you for the replies. I am slowly checking my gear since it has been sitting. Kind of taking a mental checklist of all
I have to do to get it all up and running. 10 meter mod is not the first thing on my list, but something I would like to do.

I was hoping to get confirmation on removing 2 ferrite toroids,  out of the 3 on the board.

The TS850 looks like it is ok. Going to check the TR5 next.

Thanks again,
Rich
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