If not the tubes, then it sounds like the something in the tank circuit is
wrong.
When you build an amp from scratch and are searching for the best place for the
band taps, as you move from turn to turn and then around the coil to find the
best spot, you see the same scenario you are describing.
It sounds like it is failing to find a resonance.
Are you dipping the plate current as you tune or are you just tuning for
maximum output power?
I don't have the circuit in front of me and it's way too late at night to pull
it out and look, but perhaps there are some fixed caps normally switched by
band and one has blown, or the switch is burned or has a bad or no solder.
Also, have you checked the signal level into the tube itself, after passing
through the input filter?
If something is bad in there, that would cause this.
Just for a test you can completely bypass those switched filters, disconnect
them and apply power to the finals just through a capacitor. This should give
you similar output power on all bands. If not then the problem is probably not
in the input filters, so you can reconnect them.
At the end of the day, the only way to fix it is to get in there and fix it.
You have to try things and eventually you will come across the significant clue
that leads you to the source of the problem.
Gud luk Mike.
BTW, there is a phenomenon I have discovered... I am 10x better at fixing other
people's radio than I am at fixing my own. I can only imagine that I am
subconsciously too emotional, too worried, something, and my mind doesn’t think
as freely as it does when working on other people's radio.
73 - Rick, DJ0IP
(Nr. Frankfurt, Germany)
-----Original Message-----
From: TenTec [mailto:tentec-bounces@contesting.com] On Behalf Of Mike Bryce
Sent: Thursday, November 10, 2016 7:35 PM
To: Discussion of Ten-Tec Equipment
Subject: Re: [TenTec] Ten Tec Centaur issues
Rick…
thanks for the advice.
It’s not my first rodeo, and quite aware of the voltages lurking inside.
I simply don’t like working on amplifiers.
Nothing wrong with the tubes. I put in a new trio of 811s and still have the
same issue.
power is produced, but on 20 and 15 meters, too much plate current and not
enough output.
All three 811’s plates turn nice bright red on the higher bands.
I’m suspecting a failed or failing shunt capacitors on the output.
Mike Bryce WB8VGE
prosolar@sssnet.com
> On Nov 10, 2016, at 2:46 AM, rick@dj0ip.de <Rick@DJ0IP.de> wrote:
>
> Mike, it is most likely a tube.
>
> PLEASE TAKE ALL SAFETY PRECAUTIONS FOR WORKING WITH HIGH VOLTAGE.
>
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