[TenTec] Ten Tec Centaur issues

[rick@dj0ip.de]

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 at 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 at sssnet.com



> On Nov 10, 2016, at 2:46 AM, rick at dj0ip.de <Rick at DJ0IP.de> wrote:
> 
> Mike, it is most likely a tube.
> 
> PLEASE TAKE ALL SAFETY PRECAUTIONS FOR WORKING WITH HIGH VOLTAGE.
> 

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