I picked up a TX-5300 on EBay for $81 and just for grins put in a set of four MRF421 transistors. Had to bring the bias down to about 0.4 Volts to keep the thermal runaway in check. Also added 150 ohms in series with 0.1 uFd between each collector and base to help stabilize it. I'm mainly using it on 7 MHz and getting about 525 Watts PEP out with 45 Watts drive. Usually run it at about 450 PEP out with 37 Watts in. With its bandpass filter and its biasing to eliminate the crossover distortion this thing really looks like one of Palomar's attempts to break into the ham world, although of course we all know which band most of them are used on. A pretty cool rig.
