I'm not an attorney, but do deal with legality issues in my line of business. I'd be careful what you do and do not publish and to whom.
It must be remembered that copyright has two main purposes, namely the protection of the author's right to obtain commercial benefit from valuable work, and more recently the protection of the author's general right to control how a work is used.
The "fair use" exemption to (U.S.) copyright law was created to allow things such as commentary, parody, news reporting, research and education about copyrighted works without the permission of the author. That's important so that copyright law doesn't block your freedom to express your own works -- only the ability to express other people's. Intent and damage to the commercial value of the work are important considerations. Are you reproducing the assembly manual because you needed to in order to criticize the quality of the schematics, or because you couldn't find time to draw your own version, or didn't want folks to have to purchase the assembly manual? The first is probably fair use, the others probably aren't.
Like I said, I'm not an attorney nor do I play one on TV.
And if I needed pgs 10-20 of the assembly manual which I do not own, and you were graciously willing to post on the forum or email to me, I certainly would thank you and leave it at that.