21-04-2013, 10:27 AM
Hello Alan, the oscillator in the old and the new circuits look like different types of oscillators hence the large change in the capacitor value across their two respective primaries, the frequency determining capacitor in the old circuit would appear to be one across the primary C502 (.01uf)
The frequency determing capacitor in the later circuit is I think C501 (.01uf) this would tie up if it was a blocking oscillator, if that is the case then you will notice that both capacitors are of the same value so far as the frequency determing element is concerned.
The capacitor (1nf) across the primaries in the later diagram could be a "boost" capacitor, it's charge being obtained during the 5763's sharp shut off period and aiding the primary during the 5763's scan time.
I could be wrong of course but the whole set up reminds me of a TV LOPTX stage.
Go to it Al.
Lawrence.
The frequency determing capacitor in the later circuit is I think C501 (.01uf) this would tie up if it was a blocking oscillator, if that is the case then you will notice that both capacitors are of the same value so far as the frequency determing element is concerned.
The capacitor (1nf) across the primaries in the later diagram could be a "boost" capacitor, it's charge being obtained during the 5763's sharp shut off period and aiding the primary during the 5763's scan time.
I could be wrong of course but the whole set up reminds me of a TV LOPTX stage.
Go to it Al.
Lawrence.
