Particularly when leaky batteries were involved, contaminated old solder tends to form beads rather than flowing nicely. In some cases, I've had to remove as much of the old solder as possible, replace wires, and use liquid flux. Battery electrolyte can seep into wires like a candle wick and travel a surprising distance.
I just stumbled upon camerabooks.com, because I was searching for Larry Lyells, who also created some of the National Camera manuals - check it out. Seems to cover more modern items than the older National Camera / Camera Craftsman / Infotech offerings.
eBay seller "Goodygifts" is another source, particularly if you seek some of Ed Romney's manuals.
I started acquiring camera service manuals in the 1980s or 90s, and even then it was mostly photocopies or microfiche.