Nine years and 3 months
after his initial post, I'd like to thank Bruno for documenting his capkit so well here
I had always overlooked the black level potentiometer because it was hidden so well on a small board (and not included at all in my capkit).
The result was that even after a good capkit, I ended up with a disapointingly dim picture on my Pac-Man monitor, even after fiddling for a long time with all the "reachable potentiometers" and convergence rings.
Also massive thanks to KID
for taking his precious time to help me with the capkit and pointing this particular potentiometer.
Now it's wake-waka-waka time!