Schematics

Hey mdgreg,
I'd be surprised if you could find a schematic for your iMac. If you're a Mac Tech and use an official iMac service manual ( called a Service Source Document ) when it comes to problems with the logic board it will say "replace logic board".
That's because no service tech deals with anything at the component level.
Probably a refurbisher or OEM manufacturer of these boards would have them. However I'm pretty sure schematics for something as new as your Intel iMac i3 27" running Mac OS X (10.6.4) will be highly proprietary.
I've been looking for years.
Richard

I am sure they would use the term "proprietary" instead of stingy 🙂

Logic board layout drawings are available for many of the Macs, especially the older ones. Full schematics may be a little harder to get if you are not a certified Mac repair person. You could try contacting Apple support and see if they can help you.