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Old Sep 28, 2009, 05:45 AM
thomasscherrer is offline
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Danmark, Hovedstaden, Ballerup
Joined May 2007
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a real TBC is the way to go for sure, but they are expensive !

you know old TV sets with a CRT have infact a running oscillator
used for the high voltage transformator, and it is locked to the incomming video sync,
you have most likely seen the scroll potentiometers on the back side ?
this sets the freerunning frequency, the more accurate, the longer time
your picture will be good if sync is lost.

you can make a system that is analog and does something like this:
take two sync separator IC's like LM1881
one is connected to incomming video, its output pulse is connected
via a high ohm resistor to a 15khz oscilator,
this osc is adjusted to be quite accurate, incomming pulses will make the oscillator
"lock" to the incomming pulses, and the lock resistor must be so high it takes a few sec
to get in lock and stay in lock when signal is lost, now feed this osc signal into another
1881 and get a nice locked sync pulse for your video,
the incomming synd is clipped away, and the new filtered sync is inserted
this kind of circuit will take a few hrs for an electronic wizz to make :-)
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