Shimano shifter schematics?
 

I'm attempting to repair a mid-1980s shimano STX shifter. So far, I've got the thing apart, cleaned the muck out of it and I'm trying to put it back together. The problem is, if I put it back together the way it was, the pawl for the thumb lever doesn't engage with the central toothed wheel (not a technical term there, I know). There's a huge database of Sturmey-Archer schematics on the web, does anyone know of a similar thing for Shimano?

The shifters are combined with a brake lever, which is a short-pull cantilever brake lever. It's a 7-speed, which operates an Altus rear mech on a freehub rear wheel. Any ideas where I might get a schematic for them? Shimano doesn't seem to have info on older parts available...

You are correct. Shimano has never ( to my knowlege ) supplied details of their shifter internals. Their line is that these are put together by precision robot assembly lines and are not servicable.
I've disassembled and re-assembled one of the levers you have or something very similar. There are steps in assembling those guys where you need to wind the spring tension up before fitting the next bit, that's probably what you're missing.

I had to do a rebuild on my tiagra lever the other day and ran into the same problem you are at. All I can say is that when taking it appart you need to take pictures/notes. Even with picts it is helpful to see a rebuild.

I spent a while just searching around before I found a rebuild, good luck in the search. Here is the STI rebuild that I found though I doubt it will help with and STX.

You've listed some disadvantages to Shimano, compared with other brands. This stuff annoys me. Their stuff has always been less serviceable than other companies' stuff.

Here is the STI rebuild:
http://www.nitrodyno.com/Ultegra-STI/index.htmlI
will see if I can find anything on a STX