Need help with sawtooth vertical scan on homemade video camera

[old_tv_nut]

Originally Posted by harry dalek

Something i never knew about before getting help on th nbtv forum was getting all the lines even you need feedback and a cap and resistor should do the trick.

Not sure what you are getting at with this statement. You should not need to add anything to the circuit as shown.

As Brian said, TR20 is a current source, which will make a very linear sawtooth on the 4.7 uF. Check that the base of TR20 is at 14.4 volts and the emitter at 15 volts. Correct operation requires there is no other current into or out of the capacitor, hence the use of the FET source-follower for TR21. If TR21 is shorted, this could cause the waveform you see.