Archer video enhancer full schematic

Recently acquired the full schematics for the Archer Video Enhancer, thought this might be of interest to folks here.

While I’m at it I’d be thankful for some help with understanding the circuit functionality.
I see the input signal being clamped and fed to an LM339 as a sync detector, which then triggers the 4538s to generate the blanking interval signals.

I’m speculating that the 555 is used to approximate the vertical blanking interval.

I don’t quite understand:

  1. How the horizontal blanking signal is used further ahead to modulate the video enhancement (Q13 and Q8 to Q14 collector, and the entire Q9/Q10 CR9/CR10 arrangement)
  2. Any of the actual amplification signal path (Q11/Q12) :face_with_monocle:

Enjoy the schematic in any case202012022-rotated.pdf|attachment (2.4 MB)

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