Zenith Space Command 600 - manual channel adjustment?

[AdamAnt316]

Hello everyone. At my grandparents' house, there sits a vintage Zenith "Space Command Six Hundred" solid-state console TV, chassis 25CC55. I'm guessing it's from the early-mid '70s, though the remote is of the earlier oval button type. Amazingly, it still powers up, though there is little to be received on it due to the digital TV switchover, so I'd like to feed it with a VCR which outputs channel 3 (no channel 3/4 switch on the back). Unfortunately, there is no channel 3 preset in the motorized tuning mechanism, and there seems to be no method of manual tuning on this set. I've tried using the Fine Tuning knob on the presets for channels 2 and 4, but can't get nearly close enough to channel 3 for a clear picture. Is there a way to alter one of the presets to tune channel 3? I looked in the back of the set, and spotted a number of what look like small knobs arranged in a circle on the back of the tuning mechanism. Are these for altering the presets, and if so, how would I use them to alter the selected preset? Thanks in advance!
-Adam