This morning, I had a slight variation on this theme. I came into the shack and I thought it would be nice to try some 144MHz FSK441 Meteor Scatter, as I've not done any serious MS for ages. A few months ago, I recommissioned one of the 144MHz amplifiers, capable of 300W or so and I thought I'd give it a blast this morning.
I set up the computer with WSJT and adjusted the drive from the FT847 - warmed the amplifier up and tried a test. Click, click, click from the amplifier with no output. Hmmm. I made a new patch lead between the rig and the amp a few weeks ago - I think it's ok - but I checked it - fine. Tried the FT817 driving the amp - same issue. I was starting to think that perhaps it was something to do with the 5el yagi, so I went to the back of the amplifier to disconnect the beam and try the vertical antenna.
And then it struck me. When I reconnected the new patch lead - I'd connected the antenna to the input of the amplifier and the patch lead from the rig to the output! With the amp not switched on I hadn't noticed! Swapped them over and I could see healthy amounts of output again.
Of course, by the time all that had been done - it was time to get on with the day, so no MS QSOs for me this morning.
A silly mistake, but at least they are always the easy ones to fix.