[TenTec] TenTec Digest, Vol 271, Issue 2

[Phil Greene]

Centaur Amp
After close inspection against schematic, the only thing I can find is R1 on the input board is a 50 ohm 25 watt instead of the called for 150 ohm 25 watt.
I skipped past it on the first go round because it is labeled 50 ohm and that is what it measured.
Can anyone confirm the correct value is the called for 150 ohm?

N4ZSA
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Sent: Sunday, October 26, 2025 12:00 PM
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Subject: TenTec Digest, Vol 271, Issue 2

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Today's Topics:

   1. Centaur amp (phil greene)
   2. Re: Centaur amp (Paul Kraemer)
   3. Re: Centaur amp (Ken Brown)


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Message: 1
Date: Sat, 25 Oct 2025 23:02:26 -0400
From: phil greene <trapperpg at gmail.com>
To: tentec at contesting.com
Subject: [TenTec] Centaur amp
Message-ID: <31BFC9E1-8BE0-485D-A7ED-D6111DBA8358 at gmail.com>
Content-Type: text/plain; charset=us-ascii

New to me Centaur amp with 572 tubes of unknown health.
Only has output on 80 meters (~500w)
10-40 meters have plate and grid current but no output
Load capacitor has no effect on any band
Tuning cap will dip grid current
Tried dummy load with same result
All resistors check good, and have cleaned band switch and it did not appear cracked nor damaged.
Ideas on where to start troubleshooting?
N4ZSA


Sent from my iPhone


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Message: 2
Date: Sat, 25 Oct 2025 22:07:22 -0500
From: Paul Kraemer <elespe at lisco.com>
To: tentec at contesting.com
Subject: Re: [TenTec] Centaur amp
Message-ID: <af20ace8-cd46-4020-a677-250c72aec44e at lisco.com>
Content-Type: text/plain; charset=UTF-8; format=flowed

Make sure your driver is putting power on the band in question. Happened
to me once.? Never assume it is.

Paul K0UYA

On 10/25/2025 10:02 PM, phil greene wrote:
> New to me Centaur amp with 572 tubes of unknown health.
> Only has output on 80 meters (~500w)
> 10-40 meters have plate and grid current but no output
> Load capacitor has no effect on any band
> Tuning cap will dip grid current
> Tried dummy load with same result
> All resistors check good, and have cleaned band switch and it did not appear cracked nor damaged.
> Ideas on where to start troubleshooting?
> N4ZSA
>
>
> Sent from my iPhone
> _______________________________________________
> TenTec mailing list
> TenTec at contesting.com
> http://lists.contesting.com/mailman/listinfo/tentec



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Message: 3
Date: Sat, 25 Oct 2025 20:57:39 -1000
From: Ken Brown <kenradiobrown at gmail.com>
To: Discussion of Ten-Tec Equipment <tentec at contesting.com>
Subject: Re: [TenTec] Centaur amp
Message-ID:
        <CAGnjFf=JFkDWN1wiCzMmB0+q1m2LJ5hsKj5gR4ttuf6StpDOFA at mail.gmail.com>
Content-Type: text/plain; charset="UTF-8"

Sounds to me like there is a broken connection in the tank circuit. My
guess is that the part of the band switch that connects additional fixed
value capacitors to the Tune and Load variable capacitors is working, but
the connection to the variable Load capacitor and the part of the switch
that shorts out unused turns of the inductor is open circuit somewhere.
Come to think of it, maybe just an open circuit to the loading capacitor
would be enough to cause these symptoms, since there may be no fixed
capacitors added to the loading on any bands besides 80 meters. I would
focus on the connections to the Loading capacitor.

DE N6KB

On Sat, Oct 25, 2025 at 5:11?PM phil greene <trapperpg at gmail.com> wrote:

> New to me Centaur amp with 572 tubes of unknown health.
> Only has output on 80 meters (~500w)
> 10-40 meters have plate and grid current but no output
> Load capacitor has no effect on any band
> Tuning cap will dip grid current
> Tried dummy load with same result
> All resistors check good, and have cleaned band switch and it did not
> appear cracked nor damaged.
> Ideas on where to start troubleshooting?
> N4ZSA
>
>
> Sent from my iPhone
> _______________________________________________
> TenTec mailing list
> TenTec at contesting.com
> http://lists.contesting.com/mailman/listinfo/tentec
>


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End of TenTec Digest, Vol 271, Issue 2
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