HP4 black pages

  • Thread starter Thread starter Alan
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Alan

Recently my HP LJ4 has been printing pages almost 100% black. (The
text is discernible with a lighter outline). The toner is all set,
not loose.
If I keep printing it usually improves, after one or two dark pages
then it's fine. Today it's up to three black pages and little
improvement.

Perhaps related, one of these pages jammed, and had to be yanked out
of the rear door.

Also possibly relevant; I don't leave it on continuously (the HP4 not
having a low power setting) maybe it needed to warm up or dry out
(it's pretty humid here). But over the last year since I bought it
this has not been a problem.
 
Alan said:
Recently my HP LJ4 has been printing pages almost 100% black. (The
text is discernible with a lighter outline). The toner is all set,
not loose.
If I keep printing it usually improves, after one or two dark pages
then it's fine. Today it's up to three black pages and little
improvement.

Perhaps related, one of these pages jammed, and had to be yanked out
of the rear door.

Also possibly relevant; I don't leave it on continuously (the HP4 not
having a low power setting) maybe it needed to warm up or dry out
(it's pretty humid here). But over the last year since I bought it
this has not been a problem.
Click to expand...

Alan
Normally if the printer is printing a completely black page then the DC
Controller has failed.
Replacement of the DC Controller would be more expensive than buying a second
hand HP LJ 4 (preferably a 4+).
Tony
 
Alan
Normally if the printer is printing a completely black page then the DC
Controller has failed.
Replacement of the DC Controller would be more expensive than buying a second
hand HP LJ 4 (preferably a 4+).
Tony
Click to expand...

Thanks; but is this consistent with subsequent (after 1-3 pages)
pages being okay?

And even the black pages are not completely black; I can make out the
text on top, at 100% black with a slightly lighter outline. Later
pages have progressively lighter backgrounds.
 
Alan said:
Thanks; but is this consistent with subsequent (after 1-3 pages)
pages being okay?

And even the black pages are not completely black; I can make out the
text on top, at 100% black with a slightly lighter outline. Later
pages have progressively lighter backgrounds.
Click to expand...

I have to say that usually when the DC Controller fails completely then the
output is totally and always black, maybe it is slowly dying. The problem is
that your options are limited.
If the Laser fails then normally the output will have no print at all and a
Fuser failure will produce an error message or very different symptoms. I have
never seen a toner cartridge fail and print all black (at least not with an HP
Laserjet) and any other failure is more expensive than a replacement similarly
aged printer. You could take the top cover off and ensure that all of the
connectors are well seated inside the printer but I still believe that the most
likely failure is the DC Controller (next most likely is a power supply, also
expensive). I wish I had better news, if you need instructions on top cover
removal I will happily post them.
Tony
 
I have to say that usually when the DC Controller fails completely then the
output is totally and always black, maybe it is slowly dying. The problem is
that your options are limited.
If the Laser fails then normally the output will have no print at all
Click to expand...

So I'm hoping that it isn't the power supply; from what I can
understand from the manual, if the DC controller dies a whole lot of
systems fail. Also, the fact that after several prints the quality is
good doesn't seem consistent with that.

I tried with another toner cart; this also printed very dark at first
and then improved; though not as bad as the original. Can't
definitively say it's not the cart as it's not factory fresh (an
opened, almost empty, one I'd stashed away months ago).

Is there a way to directly test the DC controller?

Around here it's not easy to find used lasers of any quality, and
transport is a problem, I have to hand carry a long way, so replacing
is not an easy option.
 
Alan said:
So I'm hoping that it isn't the power supply; from what I can
understand from the manual, if the DC controller dies a whole lot of
systems fail. Also, the fact that after several prints the quality is
good doesn't seem consistent with that.

I tried with another toner cart; this also printed very dark at first
and then improved; though not as bad as the original. Can't
definitively say it's not the cart as it's not factory fresh (an
opened, almost empty, one I'd stashed away months ago).

Is there a way to directly test the DC controller?

Around here it's not easy to find used lasers of any quality, and
transport is a problem, I have to hand carry a long way, so replacing
is not an easy option.
Click to expand...

Not sure what to suggest, best way to confirm the cause is to swap parts from
another known good printer. Obviously that is difficult in this case.
You can eliminate the formatter by doing an engine test - as follows
Open the multipurpose tray, look inside and up to the right and you will see a
small button - pressing this should produce a page of black lines, they should
be sharp and clear. If this "consistently" works OK then the formatter is
faulty (very unlikely with the symptoms you have described).
If you are sure that the Toner cartridge is not the problem (again, very
unlikely that it would fail in this manner) then you have only two likely
causes -
1. DC Controller
2. High Voltage Power supply

DC controller failure does not always produce other symptoms and the symptoms
it does produce can gradually appear (like any electronic failure).
As suggested previously it may be worth making sure that the internal
connectors are making good contact, remove the top cover and unplug/reconnect
the connectors you can see.
Tony
 
Have you tested it with a different Toner cartridge??
Click to expand...

Yes, almost the same. But it wasn't a new one so that's not
definitive.

I have found if I leave the printer on that after a few black/very
dark pages it gets back to almost perfect.
 
Yes, almost the same. But it wasn't a new one so that's not
definitive.

I have found if I leave the printer on that after a few black/very
dark pages it gets back to almost perfect.
Click to expand...

I'm wondering if the transfer roller has deteriorated, and doesn't work
properly when cold. Easy to replace (30 secs) but means finding
another...any printers you can borrow one from?
 
I'm wondering if the transfer roller has deteriorated, and doesn't work
properly when cold. Easy to replace (30 secs) but means finding
another...any printers you can borrow one from?
Click to expand...

No free parts I'm afraid, I work from home, this is my one and only
laser.
The sudden onset of this (perfect one day, black the next) seems
unlikely to be a "deterioration" problem, which I'd expect to appear
more gradually.

Elsewhere I have the suggestion of a damaged electrical contact; I'll
see if I can check that out over the weekend.

Just when I was feeling smug over my "indestructible workhorse" ....
 
No free parts I'm afraid, I work from home, this is my one and only
laser.
The sudden onset of this (perfect one day, black the next) seems
unlikely to be a "deterioration" problem, which I'd expect to appear
more gradually.
Click to expand...

Sorry, must have confused you with someone who had taken one out of
storage!
 
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