This is almost certainly thermal drift from heat. > seem OK, the power from driver and the power output remain stable > during key-down, but the current increases... > What could be the issue? > Before spending more time on troubleshooting, has someone had and > solved the same problem?
Poor heatsinking of transistors will cause this, so make sure he used the CORRECT very light amount of any heatsink compound and that the transistors are clean underneath and bolted to correct tightness. Also a very small upward drift in bias voltage will cause this. This can be because of leaky series pass bias transistors or bias pass transistor heating from inadequate heatsinking. ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
