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[Yaesu] FT-101 Fan Mod, Ed and Carol

To: <yaesu@contesting.com>
Subject: [Yaesu] FT-101 Fan Mod, Ed and Carol
From: WD8JJA@arrl.net (Davis_R)
Date: Tue, 17 Dec 2002 13:10:59 -0500
Regarding the "Fan Mod", I have done it on my FT-101, and yes it works.
I also installed a thermal switch in the PA compartment which bypasses the
switch if the PA gets hot enough.
That way, if the tubes get hot enough, the fan will stay on, even after the
heater switch is turned off, until the tubes cool down.
Before I did the fan mod, I always let the tubes cool down after switching
the heaters off,
monitoring the exhaust air with my hand.
I am not really convinced that the tubes needed the fan after you turn the
heaters off.
They would maybe be fine if they just cooled off gradually, bathed in their
own heat.
But I have done this with my rig since 1976, and I still use those tubes at
about 150+ watts out. So I wouldn't argue with success.

One catch though -- if you ever use the FT-101 on 12 VDC and switch to CW
mode with the heaters off,
the two yellow wires you tied together will cause the sidetone oscillator to
stay on continuously.
This happens in DC only, with the heaters off, because the sidetone
oscillator needs a negative bias
to turn off, this is only provided by an AC voltage from the power
transformer, which will not be there.


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