The QL Service Manual is the official guide to fault diagnosis and repair of the Sinclair QL home computer.
It was first published in 1985 and went through at least 3 revisions and contains circuit diagrams, fault diagnosis, system test, parts list and disassembly/assembly instructions for the QL.
Unfortunately, it only contains diagrams and parts lists for the issue 5 and issue 6 motherboards.
A copy of the issue 3 version (November 1985) can be downloaded (as a rather large PDF) from The world of Spectrum
Title: QL Service Manual
Author: Thorn (EMI) Datatech Ltd
Publisher: Sinclair Research Ltd
Year of Publication: 1985
Commercial Status: Commercial
Price as at May 1985: Unknown
Reviews: Unknown
ISBN: Unknown