I repaired a Wouxun KG-UV920P for a friend about 6+months ago.
The symptoms were that it drew 10A on tx, both bands, no RF output.
The PA FET got very hot, but it was not faulty, the fault was the driver FET. The circuit of the radio is a proprietary secret, and you have to think carefully about buying these things when this is the case. So without a circuit, I am guessing, but my guess is that the PA bias is such that it draws quite high current without drive.
Wouxun have produced at least three variations on the above model with changes in the driver circuit. In our case, they recommended a further mod to reduce to supply voltage to the driver, and that seems to have been successful. (I wrote the repair up, but VK1OD.net is no longer online. The mod was to take supply for the driver from the 8V regulator.)
I found out later that the owner had operated the radio sitting on his desk on full power. This has almost certainly contributed to the original failure as it denied free flow of air the the heatsink under the radio.
Most of these radios run very hot, and adeqate cooling must contribute to longer life.
Above is a pic of supplementary cooling for my IC2200H which otherwise reaches case temperatures in excess of 75° even though free air movement is unobstructed. The fan is thermostatically controlled, more at
http://owenduffy.net/blog/?p=877.
The fashion these days is to produce radios with very high output power in a quite small package, and invariably the cases reaches very high temperatures.
Owen
