HP LaserJet II printing with shadow and shade
Wong Sai-kee
I have a NeXTLaser which use same toner and paper feeder as HP LaserJet II.
Last year, it started printing with shadow (shadow of the content repeated
once after 9.5cm (4 inches)) and shade (gray dirt on the white paper). The
problem now became more serious. There is no service available for such
printer in Hong Kong. Anybody has idea on how to repair such symptom ?
Thanks in advance.
Mr.Sai-Kee
Pete Peterson
Wong Sai-kee <skw...@mae.cuhk.hk> wrote in article
<6jin4g$1...@eng-ser1.erg.cuhk.edu.hk>...
Have you tried a new toner cartridge? I can't anything else that could
cause that problem.
Pete
Robert Blackshaw
skw...@mae.cuhk.hk (Wong Sai-kee) wrote:
>I have a NeXTLaser which use same toner and paper feeder as HP LaserJet II.
>Last year, it started printing with shadow (shadow of the content repeated
>once after 9.5cm (4 inches)) and shade (gray dirt on the white paper). The
>problem now became more serious. There is no service available for such
>printer in Hong Kong. Anybody has idea on how to repair such symptom ?
The four inches probably represents the circuference of the image drum
since the drum is not large enough to print a whole page in one revolu-
tion. This coulb be the ground contact that contacts the drum in the center
or it could be a failure of the erase circuit (basically just a strip of
lamps) or a high voltage problem. The toner cartridge could be the
problem but I imagine that you have used more than one since last
year, if not try changing the cartridge. Clean all the contacts at the
back of the opening where you insert the cartridge.
Bob
Tony Duell
Robert Blackshaw (blck...@clark.net) wrote:
: skw...@mae.cuhk.hk (Wong Sai-kee) wrote:
: >I have a NeXTLaser which use same toner and paper feeder as HP LaserJet II.
: >Last year, it started printing with shadow (shadow of the content repeated
: >once after 9.5cm (4 inches)) and shade (gray dirt on the white paper). The
: >problem now became more serious. There is no service available for such
: >printer in Hong Kong. Anybody has idea on how to repair such symptom ?
If it is a Canon SX printer engine, then read on...
: The four inches probably represents the circuference of the image drum
Yes, that sounds about right - I've just looked at a spare toner
cartridge and the photosensitive drum is just over 1" in diameter.
: since the drum is not large enough to print a whole page in one revolu-
: tion. This coulb be the ground contact that contacts the drum in the center
: or it could be a failure of the erase circuit (basically just a strip of
: lamps) or a high voltage problem. The toner cartridge could be the
That sounds right. I doubt it's the erase lamp if the problem happened
gradually, because the 5 lamps are in series. Easy to check though -
there's a pair of contacts on the end of a plastic bar coming down from
the top cover that slot into the left hand end of the fuser when the
cover is closed. Check for continuity between the 2 contacts on the cover
- if they test open-circuit then one of the lamps has burnt out.
If you still suspect the erase lamp isn't working, then you chould check
Q331 nad Q333 on the PCB at the left side of the fuser and the resistors
around them. I've never had those fail. It could also be IC213e on the DC
controller, but that's extremely unlikely.
EHT problems are rather more nasty to sort out. The EHT PSU is full of
custom components - most of the circuitry is a hybrid, and there are also
custom transfomers in there. And no spares are available AFAIK - Canon
claim it's dangerous to repair the EHT unit (which is simply to sell more
modules IMHO).
There are 3 EHT supplies in the SX engine - a primary corona to charge
the drum, a toner feed voltage to transfer toner onto the exposed parts
of the drum and a transfer corona to transfer toner from the drum onto
the paper. I would guess the first one, which comes from the leftmost
push-on terminal on top of the EHT transformer I think, is the problem here.
If you need it, I can measure the EHT voltages in a working SX printer
(they're a few kV, so you'll need an EHT voltmeter) so you can compare
them to the ones in your machine.
: problem but I imagine that you have used more than one since last
: year, if not try changing the cartridge. Clean all the contacts at the
Yes, do that first. I've had impossible-to-trace SX problems caused by a
defective toner cartridge.
: back of the opening where you insert the cartridge.
Aren't you thinking of the CX here? The SX EHT connections are on the bottom
part of the printer just in front of the EHT PSU.
: Bob
-tony
Robert Blackshaw
a...@p850ug1.demon.co.uk (Tony Duell) wrote:
>Robert Blackshaw (blck...@clark.net) wrote:
<snip>
>: problem but I imagine that you have used more than one since last
>: year, if not try changing the cartridge. Clean all the contacts at the
>Yes, do that first. I've had impossible-to-trace SX problems caused by a
>defective toner cartridge.
>: back of the opening where you insert the cartridge.
>Aren't you thinking of the CX here? The SX EHT connections are on the bottom
>part of the printer just in front of the EHT PSU.
Guess I was as my three lasers are all CX based. And the poster's machine
is SX engine based. Onliest problem I've had to work on with an SX machine
was the $0.48 gear losing teeth in the fuser assembly. That's why I was
taking a guess about the drum circumference as the CX drums are
bigger.
Bob
Bob
Gregg
On Sat, 16 May 1998 21:39:52 GMT, Robert Blackshaw wrote:
//snipped//
>Guess I was as my three lasers are all CX based. And the poster's machine
>is SX engine based. Onliest problem I've had to work on with an SX machine
>was the $0.48 gear losing teeth in the fuser assembly. That's why I was
>taking a guess about the drum circumference as the CX drums are
>bigger.
Sounds familiar. Might this be the same engine used in the Canon
LBP-8 Mark III?
Where did you purchase this $0.48 gear?
--
... Gregg