Optimizing Print Quality on HP LaserJet Printers

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            Optimizing Print Quality on HP LaserJet Printers

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There are several ways to optimize print quality on the HP LaserJet II,

IID, III, and IIID printers, involving cleaning, paper selection, and

cartridge preparation.  The instructions below reference page numbers in

the LJIII User's Manual -- similar instructions can be found in the

Cleaning and Maintenance sections of your LaserJet printer User's Manual.

Start by cleaning the following:

 1. Clean the printer with a damp cloth as described on page 6-15 of the

    User's Manual.

 2. Clean the Transfer Corona Assembly as per page 6-13.  Note that the

    Transfer Corona Wire is located below the nylon diagonal wires that

    cover the Transfer Corona Assembly (see illustration on page 6-14).

 3. Clean the static discharge pins that are adjacent to the Transfer

    Corona Assembly, using the brush end of the green cleaning tool (see

    page 6-18 of the User's Manual or the installation manual that came

    with the toner cartridge).

 4. Set the Print Density dial to 5.

 5. Clean the Primary Corona Wire (located in the toner cartridge) as per

    page 6-16 of the User's Manual or see the cleaning instructions below.

Paper quality and consistency has a profound influence on print quality.

Obtain a a fresh ream of quality photocopier paper (ie Xerox 4024 or

equivalent) and load the tray with just the quantity of paper you will

print in one day.  Paper left sitting in a tray or an open ream will take

on the humidity of the surrounding environment and give inconsistant

printing.

Finally, distribute the toner by vigorously rocking the toner cartridge.

First, rock it 15 times _end to end_ by turning the cartridge to a 90

degree position and back.  Then rock it 15 times side to side.  This is

especially important with new cartridges as there is not much head space in

the toner cavity so it is more difficult to distribute the toner evenly.

To further optimize print quality, try printing the same page 2-3 times or

print 4-5 totally black pages prior to the desired page.  The high rate of

coverage involved in printing a black page refreshes the toner development

system and usually results in greatly improved consistency and print

quality.  To print a black page, send the following commands to the

printer:

    <Esc>&l0E                 ;set top margin to 0

    <Esc>&l0L                 ;disable perforation skip

    <Esc>*p0x0Y               ;cursor position to top left corner

    <Esc>*c2400a3300B         ;width and height for rectangle fill

    <Esc>*c0P                 ;fill area with solid black

    <Esc>E                    ;eject page, reset printer

You can send these commands from a programming language like Basic, or you

can create a file in Edlin with these commands and copy the file to the

printer.

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                    Cleaning the Primary Corona Wire

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The primary corona wire is located inside the toner cartridge and can be

cleaned quickly and easily. Please see the "EP-S Cartridge Installation

Manual" that comes with every new toner cartridge or the maintenance

section of your LaserJet printer User's Manual for the cleaning procedure.

If you have difficulties, you can call the Personal Peripherals Assist Line

(PPA) at (208) 323-2551 and ask someone to walk you through the procedure.

The easiest way to clean the primary corona wire is to follow the

instructions in the toner cartridge installation manual (it has

illustrations), If you can't locate the manual and can't call PPA, the

procedure is listed below.

                  Primary Corona Wire Cleaning Procedure

Note: The primary corona wire is fragile and should only be cleaned as

required.

 1) Remove the toner cartridge and the green cleaning brush from the printer.

 2) Place the cartridge in front of you so that it's oriented so you can read

    the instruction label on the cartridge. Note that at either end of the

    label there are green arrows, the arrows should be facing AWAY from

    you.

 3) On the right side of the cartridge there are two levers that operate two

    plastic shutters. In between the shutters there is a slot with a black

    plastic film in it--inside that slot is where the primary corona wire

    resides.

 4) Hold the green cleaning brush in a vertical position with the bristle end

    up and the felt end down. Note that as you hold the brush in this

    vertical position that you can turn it four ways--that is, the felt pad

    can be facing you, facing your left or right, or facing away from you.

 5) Turn the brush so that the felt pad is facing AWAY from you, and insert

    the felt end in the right end of the slot. The black plastic film will

    slide away and the felt end will disappear completely into the slot.

 6) Slide the brush back and forth the length of the slot 2-3 times. As you

    slide the brush you should hear a high pitched squeak. The squeak is

    very important:

    - it shows you have made contact with the primary corona wire and that

      the wire is being cleaned

    - it sets up a vibration in the wire which will help slough off the

      excess toner

 7) Slide the brush back to the right end of the slot, remove the brush and

    reinstall the cartridge and brush in the printer.

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                Correcting Smudges on HP LaserJet Printers

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Print quality problems on HP LaserJet Series II, IID, III and IIID printers

can often be easily diagnosed and corrected when the symptoms are

recognized.  One of the symptoms is smudges on printed output.

A smudge may be an area on the page that is gray or cloudy.  It may look

like a brush stroke or a seam through the print.  If the smudging is

located on the upper third of the page, the cause is commonly contamination

of the electrostatic discharge teeth.

Electrostatic Discharge Teeth

The electrostatic discharge teeth are located on the rear edge of the

transfer corona assembly just behind the corona wire channel under the

monofilament line.  The teeth are black, small and look like saw teeth.

As paper advances past the transfer corona wire a (positive) charge is

applied to the back of the paper.  The charge attracts toner from the EP

drum to the paper.  As the paper advances, the paper adheres to the EP drum

until the combination of paper stiffness and the discharge effect of the

static teeth allow the paper to be separated from the drum.  The static

discharge teeth bleed off the positive charge put on the paper by the

transfer corona.  If the paper does not separate from the EP drum soon

enough, residual toner on the drum will be transferred to the paper

resulting in a smudge.

Paper does not separate readily from the EP drum if the paper's surface

resistivity is high or if the static discharge teeth are not effective in

discharging the paper.

Clean the Teeth

The teeth become ineffective when, over time, they become contaminated by

paper fiber, toner or other incidental debris.  Contamination may be on the

teeth themselves or on the ground connections below the transfer corona

assembly or high voltage connector assembly.  If the ground path for the

paper's static discharge is inhibited, simply cleaning the transfer corona

assembly (top and bottom) is usually effective in correcting the problem.

Replacing the assembly is an option, if cleaning is ineffective.

Protect the Paper

Other causes of smudging may relate directly to the paper or the

environment. Paper surface resistivity increases as the paper dries out.

This can happen when paper is improperly stored.  Smudging typically arises

during winter months when heating systems dry the air in homes and offices.

When the paper dries out, the static charge is high; the paper may cling to

the EP drum and cause smudging to occur.

Smudging caused by dry paper may be most apparent in duplex mode on the HP

LaserJet IID or IIID printers.  Because the paper is printed on both sides,

the paper passes through the fusing assembly twice.  On the first pass

through the fuser, the reverse side is printed; the second time, the front

side of the paper is printed.

Paper which is excessively dry will dry out even more after passing through

the printer's fusing assembly for the first time.  On the second pass, the

surface resistivity will be higher and the paper may not easily separate

from the EP drum.  Smudging in this situation is easily identified because

the front side of the page will have the smudges and the reverse side will

not. It's important to look for the root cause of the smudging.  Is the

paper or environment dry?  Is the printer contaminated with paper fiber,

toner or dust?

ADVICE

1.   Keep the printer clean.

2.   Keep paper reams wrapped until ready for use.

3.   Check that the interior environment is not overly dry due to heating

     or air conditioning.