I was about to start a new thread asking what this weird video cable I just found in this box of cables was
most CRTs would take even up to an hour to reach their correct bias. For example, you wouldn't be calibrating a CRT color monitor until it was on for at least an hour. Of course those old monochromes wouldn't need calibration but the real point is that CRTs do take time to ramp up for full readiness. Granted from a use perspective you could begin work as soon as the picture would display which would be only a few seconds.Wow!
Warm up time: 20 minutes to meet all specifications!!! Twenty. Minutes. Not seconds... minutes!