Main issues are alignment, head cleaning, chassis cleaning, lube.
Funny enough, it's not much different from a car engine. And like a car, you can easily screw up an expensive item with the wrong methods and items.
1. Clean the heads ONLY as needed, not as preventative maintenance. Heads are delicate. (Some people use Q-tips, and it's analogous to cleaning your own intimate/private anatomical parts with sandpaper and a steel brush. Obviously that's bad!)
2. Gravity makes units go out of alignment over time, and it can be affected by head condition as well. This drift must be gently calibrated. The best alignment is done with scopes, but you can eyeball it with experience (which I have).
3. Lube can be badly done, and with the wrong items. I've read stories of morons ruining their decks with WD40. Silicon grease, etc, as needed. Again, not normal maintenance, only done when problems present.
4. Body cleaning is preventative, using soft brushes and canned air, to prevent dust/grime from affecting lube and heads. Just be careful with canned air, you don't want spew.
I thought the service manual for the 9911 was in this forum? If not, for your needs, almost any JVC service manual will do, though obviously get as close as possible (9900, SR-V101, etc).
I actually have a 9911 parts deck, if needed -- but noting it's a part decks because some parts failed/broke.
Deck maintenance can be DIY, but you must be careful. And on your very first clean job, mistakes are common. So if you insist on a DIY, never start with your best deck. Preferably even with a deck that doesn't matter at all (ie a $9 Goodwill VCR).
I could always grade your deck.
