[Yaesu] Low output on FT902

[Jon Klinkhamer]

I’m replacing all my tubes (6146B’s and 12by7) with new ones. Using 6146W’s for the finals.  The reason is I’m seeing low output. The output is maybe 80 Watts at the low bands to just barely hitting 100Watts at the high bands. I neutralized the finals as best I can and aligned the Tx drivers without any noticeable changes. But the thing I also noticed was that during my 10 second tune up, my wattmeter would show that my power was drifting downward by about 10 watts or so. My thinking is that maybe one of those big old caps is not holding the charge. I suppose the electrolytic dries up after 20 or so years.  Does anyone have any comments on this before I start to replace components? One thing I’m going to do is check the bias voltages on the tube sockets and make sure they are within the noted voltages in the service manual. 

 

Thanks for reading,

Jon