Commodore was pretty inconsistent in their service documentation. Referred to as Service Manuals or technical specifications, they were often just a set of schematics. This page will include any official documentation that I feel includes important service information so some users manuals may be found here. Be aware that some Commodore Service Manuals have the same part number (i.e. the C64/C64C and Model C16 service manuals are both 314001-03)
This post is a work in progress list of all the high quality official documentation I can find. I will also indicate which ones I have in my collection with an * since I want to build a collection of them. Links will be included when I can find a decent quality scan on a trustworthy site like archive.org.
8-Bit Computer Manuals
B Model Computer Service Manual *
Date: January 1985
Part #: 314010-06
Contents: Service manual for the B128-80 and other B Model computers. These are essentially the last Pet models and include a SID chip.
I have the physical manual but cannot find a decent one online.
Model C64 Computer Service Manual (Early) *
Date: March 1985
Part #: 314001-02
Contents: Parts List, Circuit Theory, Troubleshooting, I.C. Pin Assignments, Schematics
Get it here on: archive.org
Model C64/C64C Service Manual (Later)
Date: March 1992
Part #: 314001-03
Contents: Parts List, Circuit Theory, Troubleshooting, I.C. Pin Assignments, Schematics
Get it here on: archive.org
Model Plus 4 Computer Service Manual (Preliminary)
Date: October 1984
Part #: 314001-04
Contents: Parts List, I.C. Pin Assignments, Schematics
Get it here on: archive.org
C-128/C128D Computer Service Manual
Date: November 1987
Part #: 314001-08
Contents: Parts List, Circuit Theory, Troubleshooting, I.C. Pin Assignments, Schematics.
This is a decent service manual for once!
Get it here on: archive.org
C-128 Diagnostic Instruction and Troubleshooting Manual
Date: November 1987
Part #: 314060-01/02
Contents: C128 diagnostics using the official diagnostic cartridge
Get it here on: archive.org
16/32 Bit Computer Manuals
Amiga 500 Service Manual
Date: October 1990
Part #: 314981-04
Contents: Theory of Operation, I.C. Pin Assignments, Parts, Troubleshooting, Schematics
Get it here on: archive.org