[old_tv_nut]

I knew it used an LC oscillator, but if you first adjust the oscillator and have it locked properly to an incoming signal, then it should be just fine for adjusting the 90 degree transformer.

By the way, I don't know why the designers used a tuned transformer to get a 90 degree phase shift. Better to use the transformer to get the impedance match needed (as they do), but not for the phase shift. The R-Y demod drive goes directly to the burst phase detector, so R-Y drive phase is stable at 90 degrees to the burst. Why not then use a simple RC circuit to get the additional 90 degrees for B-Y drive? It would not need tuning to obtain the correct and much more stable angle.