Not too long ago I got a lot of help here diagnosing a stuck frequency display on one of my K2s. It was determined that both the encoder and U3 needed replacing. Being a thrifty ham
and with some good advice from KA7OEI about using alternate encoder parts, I decided to try a different part that is about 1/3rd the cost of the original Elecraft part. Happily, it worked, though the mounting of the new encoder was a bit challenging. All the details are here:
The Encoder Fix Is In73,
Casey, TI2/NA7U