Al,
Interesting. I have one of the ATU-10s that will sometimes find a tune and sometimes will not. I assumed it was a problem with the hardware and when I opened it noticed the use of glue around the coils, relays, and batteries. That would make replacing a coil or relay difficult to do. So, I haven't pursued trying to figure out what the exact problem is. I'm surprised to learn that you can get your unit to manually tune. That may mean my assumption was incorrect.
73,
Scott
AK5SD
Scott Dupuie