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 case! 202012022-rotated.pdf (2.4 MB)

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I had missed this post…welcome to Scanlines @pinigrigio and thank you for sharing these schematic, great first contribution!

FYI I just edited it as the link to the PDF file wasn’t working (I blame gremlins).

Also maybe we will later move the PDF into the #wiki (which will gradually move to At the page Video DIY schematics we already have two Archer devices but @pinigrigio’s one is different.