Quasar VR-1000

[old_tv_nut]

This is an adjustment to make the free-running head speed approximately match video vertical rate when recording.

Speculation:It could be that some component in the servo loop has drifted, so that you are compensating for that when making this adjustment in record mode. Then when you go to play mode, there is no video input and the offset shows up.

In any case, there must be a malfunction causing it to run at a different speed on playback. You could try adjusting it for correct playback speed (as seen via your USB capture) and see what voltage readings you end up with in this record procedure.

Servos are hard to debug because if there's an error in one part of the loop, another part will compensate until it's so bad you exceed the pull-in limits.