Need help with Sylvania Superset

[merlyn]

I am working on a Sylvania Superset Model # CX8172W Chassis # E44-3 (Nov. 1978)
Sams Photofact 1731-2.

I have sound but no raster. Power, vertical, horizontal, HV, and picture tube all normal.
I am losing the video waveform at the video buffer transistor Q211. If I remove this transistor,
video is normal at the base. I have isolated all the circuits that Q211 feeds except
IC400 (AGC amp, SYNC SEP, 3.15 Khz osc.) Thinking of an RF-AGC problem in the tuner, I also
disconnected AGC going to UHF/VHF in tuner, problem still persists. As long as Q211 is present
and feeding video to the AGC circuits, the video is going "off-channel", I believe I am seeing
snow on my scope. If I remove Q211, the correct video waveform returns. I have replaced IC400 twice,
and many other surrounding parts too numerable to mention here. The only thing wrong with IC400 is the
phase-det waveforms are wrong, and pin 8 (sawtooth wave for phase det) reads too high
at 18.90 vdc which is near source voltage for the chip...19.97 vdc. Pin 8 should read 5.39 vdc.
But I have replaced IC400 twice along with many surrounding caps and the two phase det diodes.
I believe this is just an effect and not a cause. Something in the AGC amp or the IF strip is causing
the video to go off channel when AGC output voltage is applied to affect the gain of the 1st IF
stage. Please help!