Did you happen to notice how you can also tune the radio by moving the
speaker up and down? I removed my speaker and use an external MFJ
ClearTone. That huge magnet directly over the vfo coil really has an
effect!
-----Original Message-----
From: Wj5mh@aol.com
To: tentec@contesting.com
To: <tentec@contesting.com>
Date: Wed, 17 Apr 2002 08:55:28 EDT
Subject: Re: [TenTec] 1320 T-Kit
> Been doing a little more troubleshooting on the 1320 looking for the
> source
> of drift after a couple minutes of transmittingâ?¦ I removed the cover
> and let
> the radio stabilize for several hours. After heating the tip of a
> nonconductive probe with a hairdryer, I touched various components in
> the VFO
> circuit, and found that oscillator Q2 (2N4124) is VERY sensitive to
> heat.
> Holding the probe to the side of the transistor will cause immediate
> downward
> drift.
>
> Varactor D1 (MV209) will also cause downward drift, but is slow to
> react to
> the temperature change. (Inserting the probe near some components
> without
> heating it does cause some change in frequency, but no drift. I took
> that
> into consideration when performing these heat tests.)
>
> Touching various capacitors in the circuit causes some upward drift,
> but the
> reaction time, to me, doesn't even approach Q2's. Personally, I don't
> see
> any way the capacitors can react quickly enough to offset any negative
> freq
> drift caused by Q2.
>
> Note: I turned the fan on when I sat down to write this e-mail, and
> listened
> to the VFO freq change. It stabilized after moving 165 Hz.
>
> Questionâ?¦ Is it normal for a transistor to be this sensitive to
> heat?
>
> Thanks for helpâ?¦and patience. (Solder connections in the VFO, buffer
> and amp
> stages have been re-soldered.)
>
> 73,
> Joe ( WJ5MH )
> Wj5mh@aol.com
>
>
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