Hi Drakelist
During a recent alignment of a T-4XC I encountered an interesting problem which I am still trying to troubleshoot. I am hoping that someone out there may have already experienced this problem and can point me in the right direction. Description of Problem: When placed in Tune Mode and loaded into a dummy load, the transmitter easily outputs 140W on all bands from 80-10 meters. Gain setting is approximately 5 (mid scale) and plate current is approximately 230 ma. However, when placed in CW mode, the gain setting must be increased to 10 (full scale) just to achieve 90W at 200 ma. There appears to be insufficient gain to drive the PA to the same power level as achieved under Tune conditions. Readjusting Plate, Load and RF Tune does not provide any additional output power. Analysis to Date: The Drake manual indicates that there is always some additional gain adjustment and sometimes repeaking required when going from Tune to CW modes but I sense the wide open gain setting indicates there is insufficient gain to fully drive the PA stage in CW mode. I tried replacing the 12BY7A driver and PAs but the problem remains the same. Now I need to understand how the Gain really works in CW vs. the Tune mode and compare the expected signal levels which the driver should be seeing to determine what is causing the difference between the two modes. I am starting to read through Gary's maintenance CDs but any suggestions on where to focus or what to measure would be greatly appreciated. Regards Wade VA3HM
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