In the last week, all of a sudden, when I transmitted with my K3, the radio would turn off. The power supply stayed on, so that was weird. It started out intermittently, but then happened every time I transmitted. I found a forum where someone said that if the radio shuts off and then when you turn it back on the radio goes back to a previous frequency, then its the power supply. Furthermore, several said its probably a regulator chip that I can just unplug and put a new one in the socket.
I purchased a second unit from HRO, and will fix the first one – which is at least 6 years old. I went with linear power supplies after an old switcher started causing hash, and on 160M – that was unacceptable.
Turns out, the forum gave great advice. The behavior had me worried that it was my K3, and I ordered a new RS-35M on Wednesday, and Thursday it was on the doorstep. Swapped out the old with the new and all is well. The best news is that I can fix the old one and then have a backup.