I have an Ameritron AL-80B that I bought second hand. I knew that it had an arcing problem when I bought it so I sent it to Ameritron for repair. They reparied it and fixed the problem (replaced the loading capacitor) and returned it to me. I have been adjusting the input coils using an MFJ-259B antenna analyzer and plastic hex tools. I was able to get 1.2:1 and most of the time a 1.1:1 swr throughout 160, 80, 40, 20 and 15 meters with no problem using this technique. Was easy with repeatable readings. Amp works great on these bands. When I tried 10 meters on the "AUX" position it was a different matter. Ameritron assured me that the 10 meter mod had been made. However, tuning the slug with the plastic hex tool makes NO difference in the swr. It remains at 2.6:1 no matter how much I turn the slug in any direction. I tuned the MFJ-259B down frequency to see where the 10 meter coil might be resonating and the lowest swr was at 21.090 mHz (!). No amount of adjustment would change that. I think that either the mod was NOT made or I have a bum 10 meter input coil to replace. Or maybe a wrong coil was installed in the first place. Any ideas or anyone have the same problem? Greg, K4PVA.