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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