Hi, thank you for contacting JustAnswer.com. My name is Russell. I will do my best to provide the right answer to your question.
This is the Canon official Service Manual for the iP6600D:
and it is, wonder of wonders, free-of-charge and free of drawbacks to access, or download.
But, it may not have the explicit and user-friendly disassembly instructions and diagrams that you need. Let me know, if it doesn't. I will hunt up other information sources that might help, if that's the case.
(But, if this does answer your question in full and adequately, please rate my answer, so that this case may be closed. Thanks.)
It does not have the information. I already have the manuals that it provides; those are the two manuals I listed in the section "What Have You Tried". The Canon repair manual clearly states disassembly instructions are not included in its content. I am looking for instructions hopefully with illustrations specific to disassembly of the Pixma iP6600D. Thanks much!!
How much (to what extent) do you need to disassemble the iP6600D, please?
Just enough to replace a logic board, I presume... ?
Your presumption is correct. I have the Canon iP6600D parts Catalog and the Canon iP6600D Service manual. The parts catalog makes it appear as if the logic board in a pretty far trip into the interior of the printer. Neither manual gives disassembly instructions.
This manual for the 6600D appears to be 'free' (with registration) and claims to be a 'workshop repair' manual:
It may (alas for non-standard sites and their methods) prove to be no more than the usual service manual you already have, no disassembly instructions in it. But, it might have what you need, too.