A little solder blob shorting out one turn of the coil. I removed it, and checked the tuning, all ok now!

I wish I had just done a quick visual inspection of everything FIRST!

It was tuning near in frequency, so it probably wouldn't have been a whole section in or out where it shouldn't be. Finally, I just happened to be looking around with a bright light and....

Another section of the switch that is on the band switch knob picks different taps on the tank coil. I checked the switch and taps, and they all looked ok too.

I isolated the capacitors on the tank and hooked up a capacitor tester. I went through all the bands and tuning ranges, and the capacitances all looked proper. That meant that it must be a problem with the inductance.

It was close... but 4.2 MHz. My first suspicion was a 100pf cap that is switched into the circuit on the bottom two bands. I replaced it, but the results were the same. I paralleled a cap, and then it worked... but that's not how the circuit was designed, and I wanted to fix it, not bandage it

Using a grid-dip oscillator which you dial in a frequency and the current will dip when the circuit under test is resonant. The tank circuit should be able to resonate around 3.8 MHz for 80 meters.

I took it apart and started poking around. There were several disk capacitors that are switched into the tank circuit depending on the frequency. I checked the switches and they seemed ok. Then I realized it would tune ok on 40-10 meters. It was just the lower frequencies with issues.

Working on a Kenwood TS820S that I had repaired several months ago. It wouldn't load up on 80m suddenly.