I recently acquired a very nice 450S at a Traverse City, MI swap. I began by having a classic problem with no audio, and traced it to the usual suspect audio coupling capacitor. That fixed the problem, and a week or so later while monitoring on 20 meters, the radio reception quit, with the CW UL "Unlock" signal. I pulled the board, and found a couple leaky capacitors on it. I checked the primary oscillator and was dead on 20.00000 mhz. I left the covers off to monitor the crystal frequency, and it played nicely for over 24 hours. I put the covers back on, placed the radio in the operating position, and felt it was fixed for good. An hour later, the dreaded "UL" cw code came on, and this time, powering the radio off, and back on after about 10 minutes, it played again for another hour. I suspect the crystal, or supporting elements around the crystal.
Has anyone else seen this problem? What's the real fix?
David