Kurzweil K1000SE aftertouch not working

I have two K1000’s - one SE and one regular. The aftertouch on the SE doesn’t appear to be working and the schematics I’ve found online (including k1000.net) don’t show aftertouch.

Can anyone send me schematics that show the aftertouch circuit? Schematics of the K1000 or K1200.

(I know my way around the internals, having repaired the SE that wouldn’t boot beyond internal diagnostics, changed displays to OLEDs and upgraded all the sound ROMs.)