"Andy Cuffe" wrote in message
...
On Sun, 6 Jan 2008 04:24:08 -0800, "William Sommerwerck"
wrote:

It's printing black lines across the width of the paper, about
1/8" to 1/4" wide. They occur randomly (two to three per page)
and look as if someone has run a Magic Marker across the
document.

If the lines are horizontal when looking at a portrait page, then it's
probably not the toner cartridge. It could be the laser, or HV supply,
or any number of other things. I would get another LaserJet 4 and
do some parts swapping. These printers are so cheap and easy to
find that it's not worth spending a lot of time on, or buying a service
manual. The toner cartridge is the most common problem. If you
get another with a bad toner cartridge (vertical lines is the most
common failure), then you can fix it with your good toner cartridge.

Thanks for the info. (The problem is solved. Keep reading.)

The service manual (which I found for free) insists that the problem is with
the printer -- the cartridge is not listed as a possible cause. An expert on
the HP forums is equally adamant that it's the toner cartridge.

I was leaning toward the printer, because I'd misunderstood how this
particular laser engine works. I assumed the points on the drum the laser
discharges print as white. They don't -- they print as black. (The toner is
charged and is repelled by the charged areas on the drum.) This pretty much
eliminates the possibility that the printer engine is at fault -- at least
in terms of intermittent laser drive. The loss of drive would cause white
streaks, not black.

So...

I schlepped the printer to "The Printer Guys" in Everett. Nice folks -- they
popped in a known-good cartridge, and two streak-free test pages popped out.
I then put my cartridge back -- and got a bad page. Barring some weird
coincidence where the printer suddenly "decided" to work for the "alien"
cartridge, I'd found the problem.

I stopped by Staples yesterday afternoon and bought a 98A. It works.

I might add that the existing toner cartridge was several years old, and had
been purchased "reconditioned". Before I return it to HP (there's a
free-shipping label in the box), I might open it up and try to get a better
understanding of what goes on inside.

By the way... The cartridges are now made in China, but HP still charges the
same price as when they were made in Japan. HP is currently selling the
P1006 LaserJet for $100 -- the same price as the 4M cartridge.