Here is one for you FT-900 owners.
I one hot day this summer I noticed my FT-900 was warm to the touch. The
cooling fan wasn't coming on. After some trouble shooting I found that
the termistor in the trigger circuit for the fan had failed.
Yaesu mailed me a couple of them at no charge. Received them in a
couple of days and installed the new thermistor. However, I didn't like
how warm the unit had to get before the fan would come on. The
thermistor is basically operating as a resistor to ground. As the heat
increases the resistance drops which activates the fan on circuit. By
placing a small quarter watt 10K variable resistor in parallel with the
thermistor I've been able to adjust the temperature at which the fan
will activate (from on all the time, to temp selected activation).
After some trial and error, about 3 attempts, I've got it working the
way I like it...keeping the rig nice and cool.
Have Fun,
dave
WA3GIN
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