Tip #1 - If your tuning becomes erratic

I currently own four FT-980s. One has every option including all the accessory filters, the iambic keyer module and an RF board that's been modified with Yaesu's "Gen TX" kit. The others are slightly less accessorized, right on down to #4 which is bare-bones and will ultimately become my bench mule for modification development and testing. Needless to say, the first rig is permanently in the lineup and is my go-to 40/75M position.

Recently, its tuning became erratic. I've run the radio in memory mode for a couple of years so it hasn't been dialed around the bands very much during that time. The VFO acted normally when tuned up the band but down resulted in no change save a KHz or so at one specific point of the encoder revolution. Almost sounds like a dirty chopper wheel, right? After removing the rig from the lineup I set it aside for a couple days (after replacing it with one of the others) and today I opened everything up to have a look. Encoder area looked clean but I blew it out with compressed air regardless.

Onto the test bench. Upon power-up everything was fine. What was changed or missing?

The memory batteries.

There is a dual AA-cell holder that's accessible under the bottom cover via a small door. I'd read elsewhere around the 'Net about weak batteries causing CPU flakiness, so here's another account of such. All of my '980s that are in service use rechargeables for their memory backups so if yours develops any frequency-control faults, there's the place to look first. An a simple fix to boot.