It might do. It might be a lot of other things
too.
Very good explanation. I'd tell him to go to
www.repairfaq.org and take
a look on the laserjet and printer/copiers texts. There are a wealth of info
there.
Some of which I contributed to.
My first laser printer used a Canon CX engine. I was given it because it
didn't work, it took me an hour or so to find a dead PAL (actually a HAL)
on the formatter board. Canon didn't sell spare chips, they wouldn't even
sell be the complete board. And they wouldn't supply a service manual.
(This was before I'd found The PrinterWorks, who would at least sell
mechanical bits and complete boards).
Figuring I'd got nothing to lose, I took the machine _completely_ apart.
And I slowly figured out what was going on. Many of the chips were
standard (the motor control stuff was also used in consumer electronics
devices -- the presence of a pin named '33/45' on the PLL chip pretty
much means it was used in a record player turntable :-)). There was some
custom stuff I couldn't really identify, but...
Fortunately (and this took a lot of working out), I discovered that
1) There was a model called the CX-VDO that didn't have a formatter
board, the external connector went straight to th DC controller board.
2) It was used on the PERQ, a machine I owned and was in love with.
3) I'd been given a few PERQ optional I/O cards in various states of
completeness, it should be possible to make one complete one.
So with much help from Bob Davis, and a lot of luck, I put it all back
together, aligned the optics using an IR remote control tester to detect
the beam, etc. Built up the PERQ interface, made up a cable, and plugged
it in. And it didn't work. But it did something. Tests showed it was
sending exactly 16 pixels from the PERQ, then giving up. Aha, that's the
data bus and FiFO width. Yes, I'd missed off a jumper on the PERQ board
that clocked the FIFO.
Anyway, a few years later, I bought (cheap) a Apple LW2NT (SX engine). I
did much the same with that. Took it apart, figured out how it worked,
and made notes. I use that printer on my PC to this day....
This has taught me a lot of things, amongst them
Laser printers are actually quite simple, although there are some tricks
(like the deliberate AC ripple on one of the EHT voltages, to cause the
toner to come on/off the drum, leading to a more even distribution)
The fact that the manufacturer won't supply a manual is no real problem
if you don't mind taking the time to produce your own.
A few months (!) spent taking a laser printer apart, putting it together,
and attacking it with 'scope and meter will tell you more than any
servive manaul or training course I've ever heard about.
Many of the laser printer repair books and stuff on the web are
downright wrong. Others simply encourage lucky-dip methods. I've yet to
see one that really goes back to first principles and tells you to start
by checking signals, etc.
-tony
