How to Upgrade, Repair, Disassemble a Hewlett-Packard (HP) Printer

Do you need to upgrade or repair your Hewlett-Packard - HP printer? Here is a collection of free take apart instructions, disassembly pictures, cleaning advice, upgrade and repair manuals, as well as do-it-yourself (DIY) tips and tricks for DeskJet, LaserJet, ScanJet, ThinkJet printers and for ink or toner cartridges. If you have written a hacking guide yourself (or if you know of a maintenance tutorial not linked here), please submit a new entry.

Hewlett-Packard - HP DeskJet 400	Nobody will mind if you pull an old Inkjet printer apart. Every house has at least one in a cupboard somewhere, kept because it cost good money back in the day, but now replaced by all in one devices which cost less than their own replacement ink cartridges. [...] older inkjets are built to last, and to be servicable rather than thrown away when they stop working. So it's possible to get inside and take everything apart without having to break components or remove rubber feet and search for screws hidden beneath stickers. These devices have evolved over time and are compact marvels of mechanical and electronics engineering. As you puzzle your way inside you get to marvel at the designers ingenuity.
Hewlett-Packard - HP Deskjet 670	Printer modding: putting a motherboard into the paper tray (in German).
Hewlett-Packard - HP DeskJet 970Cxi	This illustrated guide provides step-by-step take apart and cleaning instructions for an old inkjet printer.
Hewlett-Packard - HP DeskJet 2000C	Disassembly and repair of the ink pumping systems.
Hewlett-Packard - HP DeskJet 2500C	A pump station repair guide.
Hewlett-Packard - HP DeskJet 5550	Power Brick Mod Guide: convert the power brick to use a traditional plug-in cord.
Hewlett-Packard - HP DeskWriter 660C	This is a serial printer, required by older Macintosh computers. Many possible failures can cause the symptom of a totally dead printer. This HOWTO focuses on the case where the power switch itself is nonfunctional, because the entire length of the trace connecting to Pin 5 had oxidized and became nonconductive: an open circuit. Same result as if the power switch itself failed: Dead Printer. If the damage is restricted to a smaller area, an easy and suitable repair can be achieved via a conductive pen, made for just this sort of PCB trace repair.
Hewlett-Packard - HP Laserjet 4+/4M+/4P/4MP/4V/4MV/5/5N/5M/5MP/5P/5SI/6P/6MP	Do It Yourself Printer Memory: how to convert 16MB standard PS/2 Fast Page modules into SIMM modules.
Hewlett-Packard - HP LaserJet III	How to repair malfunction "50 SERVICE", by checking the fuser and soldering "pseudo" resistors on different PCBs.
Hewlett-Packard - HP LaserJet III	A complete step-by-step disassembly guide with pictures (in German).
Hewlett-Packard - HP LaserJet IIISi, 4(M), 4Si(MX), DJ 1200C(/PS), PJ XL300(/PS), DnJ A/B, DnJ 200/220 and DnJ 600	Printer Memory Explained (PS/2 SIMM). Expanding the memory of your LaserJet or DesignJet.
Hewlett-Packard - HP LaserJet 6P	Exit Roller Replacement Repair.
Hewlett-Packard - HP LaserJet 1100	How to replace the feed roller and the fuser.
Hewlett-Packard - HP LaserJet 1100	Troubleshoot chronic paper jams. Examine the pickup roller and the separation pad and spring.
Hewlett-Packard - HP LaserJet 2100, 2100m, 2100se, 2100n, 2100xi, 2100tn	Illustrated lid removal instructions, to replace the feed roller.
Hewlett-Packard - HP LaserJet 2600N	This printer seems to have a defect with its fuser. This tutorial explains in short how to replace the unit.
Hewlett-Packard - HP Network Scanjet 5	Hard disk replacement, power supply repair, pictures from the inside and conversion to FreeBSD.
Hewlett-Packard - HP ThinkJet	How to recell a dead printer battery pack is dead.

Manufacturer Information, Customer Service

Hardware Maintenance Manual, User Guide, Service Manual

As far as I know Hewlett-Packard - HP doesn't provide free service manuals.