As I play with my now-working mechanical televisor, I have noticed that there appears to be some 'heat sensitivity' to the setup. If I startup 'cold', the setting I have for the motor speed control pot of the motor circuit isn't enough. I have to turn it up. After a while, I have to turn it down, as it runs too fast and loses synch.
Likewise, with the 'double speed' testing, sometimes I notice that I can't turn the pot far enough to get the motor to go fast enough -- and other times, it's plenty, and the motor will run OK.
I'm suspecting the motor speed circuit because when I remove the IR led signal, the motor literally takes off -- roaring into way past the needed speed. It seems to me that there's some characteristic of the circuit -- the PLL chip, perhaps, that is rather sensitive to temperature (?).
This annoys me a bit, because I can't set that speed control pot to a set position and leave it. In any case, I'm considering moving that pot to my front panel as a user-control, to allow the playback of out-of-standard frame rates. Another interesting observation, the speed control can be used for vertical centering of the frame -- plus or minus, say, a quarter-frame in size. I imagine this would normally be done by adjusting the position of the IR pair.