Much thanks to all who contributed to the thread regarding my OMNI C. I'll
save you the long and whining road of my internal torment, but I ended up
going with a matched pair of Motorola MRF458s (same as original). I took
the middle road between "it's not worth fixing" and "better than original
parts".
Including a shipping and a pair of 3.3 ohm resistors to replace two which
had developed a tan, the repair was just under $70 -- not including a much
needed upgrade to my soldering station.
Final assembly and checkout revealed another problem, possibly what caused
the meltdown in the first place. The 13.x volts to the PA goes to a
pass-thru connector consisting of a nut, screw, insulators, and two
star-washer type solder lugs, one on the inside an one on the outside.
The solder lug on the inside had developed a high resistance (hundreds of
ohms) between itself and the pass-thru nut/bolt. This resulted in a low
voltage to the finals, but proper voltage to the driver stage which has a
separate power pass-thru. It wouldn't be hard to see how that could blow
the finals.
I replaced the MRF458s without incident, cleaned up the 13.x VDC power feed
through, and had previously found and replace a leaky sense diode in the
SWR meter circuit. All seems back to normal, except for my frayed nerves
whenever I turn up the DRIVE control.
Thanks again to all who contributed answers to my original thread!
Paul
AC8OI
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