This CONN ST-11 Strobotuner from the 70's wasn't staying in calibration so it couldn't lock on to a note when tuning. I took it apart to see if I could get it working and while I was investigating, I looked at the schematics and put a few signals on the scope.
0:00:00 What is a strobotuner 0:03:16 Block diagram 0:05:56 Tear down and look inside 0:08:39 Schematic overview 0:12:58 Schematic main oscillator 0:17:59 Schematic clock divider 0:20:18 Oscillator signals on the scope 0:24:17 Working demo of strobotuner