Kind of dated, though:
But I am finding it useful. Are there more or better (free) guides out there?
Atari - The BOOK - Guide to Electronic Game Operation & Servicing : Atari : Free Download, Borrow, and Streaming : Internet Archive
This book was written by Atari in 1980 specifically to teach people who had bought their arcade games how to repair them. As you might expect, The Book assumes...
archive.org
But I am finding it useful. Are there more or better (free) guides out there?

