David Nebenzahl wrote:
....
I need a wiring diagram for ...variable-speed...reversible drill. ...
...I replaced the speed control ...has worked since, but not correctly
...
Here's the deal: it works, but not like it used to. At slow speeds, it
feels like it's "chugging" or cogging. No sparks from the brushes. At
medium speeds it runs a little smoother with minimal sparking, about
what you'd expect. At high speed, it runs with a lot of sparking, more
than it should.

The commutator is in good condition: I cleaned it and scraped out all
the built-up crap between the contact bars. Brushes are in good shape. ...

If it runs and variable speed is functional, it isn't a simple wiring
problem. The spitzen-sparken and erratic running at low speed is
indicative of the brushes not fitting correctly. I'd hazard a guess
the combination of "cleaning" the commutator and perhaps turning the
brushes around or otherwise getting them mis-aligned is the primary
problem...