You may be interested to know how I got into laser printer repair. It's a long story, but here goes...
I was given a non-working Canon LBP8A1. I pulled the case and started fiddling about and discovered a PAL on the formatter board with a stuck output. The cure was obvious -- replace the PAL.
Alas Canon didn't like that solution. No parts were available, and no manuals. At about this time I discovered that the original printer for a computer that I happen to love - the PERQ - was a CX-VDO -- the same printer without the formatter. And I managed to obtain the PERQ interface board, admittedly non-working.
So I totally dismantled the printer in the hope that I could figure it all out. I had a pile of screws, gears, lenses, mirrors, bearings, etc. And PCBs covered in unidentifiable chips.
A lot of work with data books (and questions to newsgroups) identified most of the chips. A lot of hacking about got me enough of the pinout of the CX DC controller connector to guess roughly what was going on.
Then I had some luck. The guy who'd given me the PERQ card remembered that the CX-VDO had a ribbon cable from that connector to the outside world. And Bob Davis, who had obtained all sorts of stuff when PERQ Systems folded, dismantled his personal machine and ohmed out cables, etc.
Slowly it all went back together. I figured out how to align the scanner unit using the IR detector I use for testing remote controls. I figured out how to test (and repair - there was a defective chip and a shorted capacitor) the main PSU. And I worked out how the status LEDs were connected.
I made up what I thought were the right cables, put it all together and fired it up. The test page was fine. I was getting there. Put the PERQ card together, plugged it all it. It sort-of worked. The page was black apart from a 16 pixel strip at the left. But Bob had been helpful and had sent me info on the operation of this card. I was my fault. I'd missed out a jumper which connected a clock to the data FIFO. After that it worked fine.
I now believe that these printers CAN be repaired at home, no matter what Canon say. And if Canon won't help people, then somebody else should...