Id start with 200pf !! and at least a 1000V DM-19 size silver mica or 5000V
ceramic RF cap.
But first since the amp was designed to work as built:
There is also the possibility that your tank circuit is upset by a leaky
plate blocking cap, shorted turns on the plate choke, crystalized solder
connections, partially fried safety choke.
Carl
KM1H
----- Original Message -----
From: "Ron Youvan" <ka4inm@tampabay.rr.com>
To: "amps" <amps@contesting.com>
Sent: Thursday, December 23, 2010 10:28 AM
Subject: Re: [Amps] TenTec Centurion - 422 tuning question
> Bruce Meier wrote:
>
>> I seem to be having a tuning issue with a recently purchased used
>> Centurion.
>> Specifically, there doesn't seem to be sufficient capacitance in the
>> LOADING
>> for 40, 80, 160. When tuning I run the LOAD cap up to 10 (MAX) and the
>> power output has not yet peaked. The worse band is 160. There the
>> 3-500s
>> get VERY red with light operating. Here is what I have done so far but,
>> in
>> my opinion, none of this should have been required as the amps do work.
>> I
>> think mine has an issue.
>
> I would add a 200 mFd at 600 Volts across the loading capacitor and see
> if:
> 1. it cures the problem on 40, 80 and 160.
> 2. you can still properly adjust loading control in your highest channel.
>
> If so you are fixed, if you have too much capacity on your highest band
> you need a new loading
> capacitor with the same minimum capacity and more maximum capacity. (by
> 200 mFd or more)
> If you are closer, but not there, try 400 mFd at 600 Volts instead of
> 200 mFd at 600 Volts.
> --
> Ron KA4INM - I'm proud to be Chuck's pop!
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