I, on the other hand, purchased my Centurion new in 1991. Sold it last year
still with the original transformer, QSK board and tubes and making 1200 to
1500 watts out. No failures and it acquired several thousand hours of
operation. I deem that proper tuning is the key to success and longevity.
While the AL-82 is a good, no very good amp but it does not offer the slick
and full QSK of the Centurion, unless one adds the QSK-5 kit. I considered
the QSK-5 kit with my new AL-80B but decided against it. I elected to go
another route.
73
Bob, K4TAX
----- Original Message -----
From: <bcarling@cfl.rr.com>
To: <tentec@contesting.com>
Sent: Sunday, March 16, 2014 8:59 AM
Subject: Re: [TenTec] Centurion Amp QSK Board
Thanks Don - I will call them tomorrow and buy the kit. Or find those 5
parts on the web.
This QSK board was already replaced once by the previous owner.
It seems to be the other one of two very weak links in the design of
Tentec amplifiers.
Power transformer and QSK board..
I love it when my 422 works right, but if I had it to do over I would
have bought an AL-82
or something similar.
73 - Bry
On 15 Mar 2014 at 22:09, Donald, K6RV wrote:
Bry,
You definitely do have a blown QSK board. Those are the same symptoms I
had - and if you re-read the email of mine below, it gives you all the
info on how to fix the board. That board is very sensitive to any
shorts, spikes or surges. Once I repaired my board, all was well, and
has been ever since. I was just lucky I did not have a transformer
problem!
Good luck !
Donald, K6RV
On 3/15/2014 9:48 PM, bcarling@cfl.rr.com wrote:
> Interesting developments.
>
> I have a newly rewound HV power transformer installed in my Tentec 422.
> It appears to be working. No more blowing primary fuses and I now see
> the 3000V or so that I expect on the Ep metering. However the
> switchover circuits are now misbehaving.
>
> If anyone has experience with the QSK board please comment - here is
> what happens:
> When I turn on the amplifier, the OPERATE and TRANSMIT LEDs are
> illuminated. The Standby LED is not illuminated. The tubes light up.
>
> If I engage the microswitch on the side of the AC / Relay board then I
> hear relays kick in and a small amount if plate current follows.
> Approx. 100 mA as I remember.
>
> On checking around inside the amp I find that U2 NAND gate on the QSK
> board is not operating correctly. PINS 11, 12 and 13 are all HIGH -
> around 12V or so. Power appears to be correct with Pin 7 at 0V and Pin
> 14 at +13V.
>
> The other NAND outputs of U2 are:
>
> Pin 3 = 14v
> Pin 4 = 0.22v
> Pin 10 = 14v
>
> Can anyone tell me why U2 would act this way and fail to follow the
> NAND logic? Any idea what is going on in my 422 to make it misbehave
> this way?
>
> Best regards - Brian Carling, AF4K
>
> >From earlier:
>
> It appears after reviewing my QSK board problem and the blown fuses in
> my Centurion, that I mis-wrote what happened. I indeed had the same
> symptoms you had: Blown fuses for no apparent reason. In my case the
> QSK board was blown, but in talking to Ten-Tec service yesterday, they
> said the sequence happened like this: There was a high voltage short
> from one of the 3-500Z tube plates to the top of the cabinet, causing
> the fuses to blow. Guess when I had replaced the tubes, one of the
> plate straps was too close to the top of the case and arced over. The
> blowing of the fuses created a surge, or a spike, which blew out the
> QSK board. The QSK board is very sensitive to the fuses being blown,
> for whatever reason. You may find, that the QSK board is blown in
> addition to the transformer being shorted. The symptom will be that the
> standby/operate switch does not work as it should, and the transmit
> light will be constantly on. If that is the case, then you can get the
> "kit" to rebuild
t
he QSK board, or send the board to Ten-Tec for them to re-build, or have
them send you a new QSK board (Cost = $97), and/or the "kit" to rebuild
your old board and have as a spare. That is what I did. The Kit consists
of 2 IC's and 5 Transistors, and cost about $20, as I remember. I know
you are concerned about putting so much money into the amp., but, in my
view, it is both necessary, and worth it, especially since you already
will have the big bucks invested in the re-wound transformer.
>
> Again, Bry, good luck !
>
> 73, Donald K6RV
>
> Message: 14 Date: Tue, 4 Feb 2014 06:18:44 -0800 From: Bry Carling
> <bcarling@cfl.rr.com> To: Discussion of Ten-Tec Equipment
> <tentec@contesting.com> Cc: "tentec@contesting.com"
> <tentec@contesting.com> Subject: Re: [TenTec] Centurion Amp. Problem
> Message-ID: <42FCECBC-F96D-40EC-ACBB-A21415410F44@cfl.rr.com>
> Content-Type: text/plain; charset=us-ascii Thank you so much. They
> never brought up that possibility during my calls to Tentec while
> troubleshooting. However the previous owner did mention to me that the
> QSK board had already been replaced. This amp is trying my patience.
> It's not just the money but the time. If I end up replacing the QSK
> board too then I will have enough into it to have bought a nicer
> amplifier. It's disappointing to think a QSK board could cause main
> fuses to blow. I will try to learn how to troubleshoot that section
> while my transformer is away being rewound. Thank you so much for the
> insight about the QSK circuit. Bry AF4K
>
> Best regards - Bry Carling
>
>
>
>
> -----
> No virus found in this message.
> Checked by AVG - www.avg.com
> Version: 2014.0.4336 / Virus Database: 3722/7200 - Release Date:
> 03/15/14
>
>
>
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