so my trusty 706 decided to crap out on me yesterday but only on 20 meters. every other band works fine, full power, good swr, but switch to 20m and nothing. not even carrier. checked all the obvious stuff like antenna connections and swr meter shows good match. anybody seen this before on the mkiig? i'm thinking maybe the band pass filters but dont want to crack it open if theres something simple im missing

had the exact same thing happen to mine about 2 years ago. turned out to be one of the relay contacts in the band switching circuit got corroded somehow. easy fix once you find it but took me forever to track down because everything else checked out fine. if you're handy with a meter you can check continuity on the relay coils when you switch bands

Check the PA bias voltage first before you go digging into relays. I've seen these develop bias issues on individual bands when the switching transistors start to go. Should be around 0.7v on the PA base but measure it on 20m vs a working band. Also worth checking if you're getting any drive to the PA stage at all with a scope if you have one