|
I'd turn the color off, and adjust fine tuning and AGC for best picture...If color don't work at that fine tuning setting then that is a separate issue that should be addressed. If you can't get good monochrome picture contrast I'd recommend checking DC voltages along the video chain. On Zenith sets you can often un-solder the video det diode or unplug the tuner and directly inject composite video at the detector output...If you see a noticable improvement in contrast with vid injection then your IF or tuner most likely have issues (check tubes, and change tubular film/paper caps first)...Though AGC could also affect RF/IF gain, and should be looked at.
Normal AGC control action should have a range of no-signal at bottom, low to high contrast, overload with sync loss and or negative picture. Adjust up till you hit overload then back down just a tiny bit below/after the point where sync returns.
|