Laserjet 4M paper comes out blank?

  • Thread starter Thread starter Ron Bean
  • Start date Start date
R

Ron Bean

I have an old Laserjet 4M that was working OK until this morning.
Now the paper comes out *completely* blank-- not even a smudge.
Self-test doesn't complain, but the test page also comes out
blank. No error messages, other than "toner low" (which it's been
saying ever since this particular toner cartridge was installed--
I assume the sensor is broken).

The suddenness and completeness of the blank output doesn't
suggest any failure mode I've ever heard of. If the fuser wasn't
heating up, wouldn't there be an error message? If the toner were
low, wouldn't there be some partial image?

I have a repair manual and I'll try taking it apart this weekend,
but I don't know what to look for. Any clues?
 
I have a repair manual and I'll try taking it apart this weekend,
but I don't know what to look for. Any clues?
Click to expand...

If it's a proper HP service manual it should have a comprehensive fault
finding guide to help you isolate the problem.

Mike
 
The suddenness and completeness of the blank output doesn't
suggest any failure mode I've ever heard of. If the fuser wasn't
heating up, wouldn't there be an error message? If the toner were
low, wouldn't there be some partial image?
Click to expand...

Yes, there is something to detect a fuser failure.

Isolate it to the formatter or the engine. Open the front flap and
locate a small hole in the top right of the opening (on the side of the
opening. Poke a pen or small screwdriver in there to do an engine test.
You should get a set of lines printed on one sheet.
 
A broken Corona wire could do this, but they do not typically just fail
like that.

Yes, there is usually a warning message if the fuser fails, and the
paper would come out with the toner on it, just not fused, so it would
smudge if you touched it with a finger.

Either it ran out of toner suddenly (can happen, but not usually that
suddenly) or something failed.

Art
 
MikeD said:
If it's a proper HP service manual it should have a comprehensive fault
finding guide to help you isolate the problem.
Click to expand...

I finally remembered where I had stored the manual, and it does
suggest some possibilities, including:

Defective laser shutter
EP Cartridge Support missing or damaged
Toner cartridge
Transfer roller voltage
Developing bias charge
Drum ground path
Laser scanning cable assembly

I should have time to disassemble the printer later tonight.
 
Earlier said:
I finally remembered where I had stored the manual, and it does
suggest some possibilities, including:

Defective laser shutter
EP Cartridge Support missing or damaged
Click to expand...

This was it-- the laser shutter wasn't opening, due to some parts
getting out of position. Once I had all the covers off, inserting
and removing the cartridge a few times told me what should have
been moving that wasn't, and eventually I got things back to
where I assume they should be. And the output is no longer blank :-).

BTW when I went to remove the screws that hold the top cover in place,
I discovered that there weren't any. Apparently some previous owner
decided they weren't necessary...
 
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