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I had an interesting problem with my 20m QCX+. At 12 volts all was well, at 13.8 volts the output power dropped and the input current increased. This occurred even when transmitting into a dummy load. Also at 13.8 volts Q5 (the T/R switching transistor) got very hot during transmit. It was obvious that Q5 was being switched on and off when it should be hard off during transmit. Suspecting RF effecting Q5, I replaced Q5 and its bypass capacitor C34 with no change in behavior.

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I did some searches and found that the original version of the QCX had similar Q5 problems which were solved by adding a resistor from the drain of Q5 to 12 volts. Both 4.7K and 10K resistors were tried with success. Clearly this is the reason the 10K R64 resistor is now part of the circuit in the QCX+. After some experimenting I got the QCX+ to work correctly at 13.8 volts by paralleling R64 with a 5K resistor thus reducing R64 to 3.3K.

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I have noticed no ill effects from this mod and just wanted to pass this along in case any one experiences the same problem or has any thoughts to add to my experience.

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Thanks and 73,

Lou? ? W2ROW