Possible Fix for Contrast Buzz?

[old_tv_nut]

"Noise gate" adjusts where the sync circuit starts to ignore high amplitude RF interference, and you don't have any. You need to find the real AGC adjustment if there is one.

The IF would have to be modified to a whole different configuration -it's not just that it's a SWIF, but also may be that it has separate video and audio second detectors, each fed by a different IF response, or other complex fooling around.

[zeno]

You can also try adjusting the audio detector coil A.K.A. quad coil.
Flag your diddle stick to be SURE you can go back !
Adjust for less buzz. Center at the least buzz point. If it takes
more than a turn I would go through the audio with new det tube & a fine toothed comb.
The SIF transformer will only effect hiss.
BTW Motos often had an "optimizer" adjustment, try that first.

SAW filter is over the top IMHO. A fun project if you are into
such things would be trying an IF strip. Get a Zenith 150-190-01
IF module & adapt it ( must be the -01 version ! ). You will need 24 V
to run it & AGC voltage. Output will be composite video & SIF. A
crazy project but who knows ?

73 Zeno
LFOD !
BTW BUZZ SUCKS