[TenTec] Centurion is on the Fritz

Fri Oct 24 12:30:34 EDT 2014

I agree all of the below. Another lead could be the QSK board which are a 
notorious weak link but perform all the recommend ;erformance checks.

If the tubes were somehow electrically or mechanically damaged then 
overheating is possible. The over heat damage could have caused by failure 
of the fan but I am certain you would have ruled that out.

Have you checked F1 on the QSK board?

Mike
W8TRN
----- Original Message ----- 
From: "Rick - DJ0IP / NJ0IP" <Rick at DJ0IP.de>
To: "'Discussion of Ten-Tec Equipment'" <tentec at contesting.com>
Sent: Friday, October 24, 2014 01:17
Subject: Re: [TenTec] Centurion is on the Fritz

> If there is a problem in seeing any power out (at all), then it is not 
> just
> a T/R problem.
>
> At a minimum, he should be seeing the 50w of drive power that is applied 
> to
> the amp because that would pass straight through to the output.
>
>
>
> If one of the tubes are blown, he should be seeing a couple hundred watts
> out but find it won't load properly.
>
> If both tubes are blown, he would see no power out.
>
>
>
> It's hard to believe both tubes would blow at the same time.
>
> More likely is an internal fuse either in the filament side or in the HV
> side.
>
> This could be caused by one of the tubes shorting.
>
>
>
> If he sees no output at all from the amp, then I would unscrew the coax to
> the input and hang it directly on a watt meter and dummy load.  Make sure
> the transceiver is putting power out at that point.
>
>
>
> It's hard to troubleshoot when all of the info is spread out over several
> emails.
>
> In order to hone in on the problem, if I were doing it I would work 
> through
> the following check list RECORDING my results for each step:
>
>
>
> ..1).  Remove all cables from the amplifier
>
>
>
> ..2).  Then connect the amplifier to a dummy load with a "measured good"
> short coax (measure with coax between the dummy and his RigExpert 
> analyzer,
> then scan 30 MHz wide, f=16 MHz).  If the SWR curve is flat across the
> spectrum, the coax is good.
>
>
>
> ..3).  Switch the amp on and check if the tubes are both lighting up to
> normal brilliance.
>
>
>
> ..4.  Switch the meter to read plate voltage and record the amount of HV 
> it
> shows.  Should be about 3400v.
>
>
>
> ..5).  Connect a short cable with RCA phono plugs on both ends to the jack
> which is used for keying the amp with a single cable.  If the amp has a 
> menu
> to select which type of keying, place it in the single cable mode.
>
>
>
> ..6).  Switch the amp from standby to operate and touch the center pin of
> the other end of this short cable to chassis ground.  The amp should key.
> If there is a standby/operate light, it should light up for "Operate". 
> Each
> time you touch the cable to ground, you should hear the relays switching.
>
>
>
> ..7).  While still touching the cable to the chassis, check and record 
> Grid
> Current (Ig).  Should be about 100mA.
>
>
>
> ..7).  While still touching the cable to the chassis, check and record 
> Plate
> Voltage. Should be about 3400v.
>
>
>
> STOP and evaluate the results.
>
> If any of these steps failed to give the expected results, then there is 
> no
> need to apply RF power to the amp.
>
> It's not going to work.
>
>
>
> If this is not all OK, then I suggest sending the amp to Ten-Tec.
>
>
>
> James has a lot of experience in working with low voltage circuits,
> especially audio circuits, but he has no formal training or lab experience
> for working with VERY high voltage.  One mistake could blow up lots more 
> in
> the amp, or as Mike pointed out, COULD BE FATAL.
>
>
>
> If all of the above tested OK (which I doubt), then check the output power
> of the transceiver directly at the end of the coax that connects to the 
> amp.
>
>
>
> - If that is OK, then set the transceiver to about 10w output, CW, and 
> then
> connect the coax back to the amplifier.
>
>
>
> -   With the short cable (2x RCA Phono) still connected to the Amp Key 
> Jack
> on the amplifier and while monitoring "Plate Current"  (Ip) on the amp,
> manually touch the center pin to ground again to place the amp in operate
> mode and then key the 10w CW.   He should see a significant rise in plate
> current.
>
>
>
> -   If that works, then do it again and quickly adjust the PLATE TUNE and
> LOAD for max power out.  Should be about 100w.  If it is, then the problem
> is, the transceiver is not keying the amp.  I don't think this is the
> problem  because he has tried a couple of different transceivers and all 
> had
> the same results.  Still, we need to check this.
>
>
>
> Somewhere in this long procedure, something will stand out and say "HERE I
> AM".
>
> That will be the clue to what has happened.
>
>
>
> My guess, the amp has overheated during continuous use as NCS.
>
> James had it mounted inside of a shelf with little breathing space.
>
> I warned him a couple of years ago that this was very bad for the amp but 
> it
> sure looks good.
>
> If he didn't move it, then this is probably the reason it burned up.
>
>
>
> Amplifiers should always be out in the open with plenty of breathing 
> space.
>
>
>
> 73 - Rick, DJ0IP
>
> (Nr. Frankfurt am Main)
>
>
>
> -----Original Message-----
> From: TenTec [mailto:tentec-bounces at contesting.com] On Behalf Of Jim Brown
> Sent: Thursday, October 23, 2014 10:43 PM
> To: tentec at contesting.com
> Subject: Re: [TenTec] Centurion is on the Fritz
>
>
>
> On 10/23/2014 10:54 AM, Richards wrote:
>
>> I have modest DIY sills and test equipment but I am game to try any
>
>> diagnostic test within my skill level.  Any ideas?
>
>
>
> I don't know that particular amp, but if my Titan were doing it, I would
> suspect the failure of the TX/RX relay. The Titan keying logic monitors 
> the
> position of the relay and won't TX unless the relay has pulled in.
>
>
>
> Another thought -- try CW and see if it works. If it does, it could be a
> failure in the audio chain. Something as simple as a broken mic cable.
>
>
>
> 73, Jim K9YC
>
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