Lexmark T640, T642 and T644 Maintenance

Parts in a Lexmark laser printer maintenance kit

This is a brief outline of the maintenance requirements for the Lexmark T640, T642 and T644 monochrome laser printer.

The operator panel displays the message 80 Scheduled Maintenance at each 300K page count interval. This is the page count that manufacturers testing has indicated significant parts wear can occur.  You usage pattern and media type can certainly affect parts wear but the display message is usually a solid indication that service is required.

The maintenance kit includes a the fuser assembly, transfer roller, charge roll, and pick tires.  The fuser assembly in the kit is available for outright purchase or on an exchange basis.

This is a task that can be performed by the user and in these difficult economic times more and more uses are choosing this path.  With the step by step instructions, available online help and email support its easy to save time and money!

HP LaserJet 4600 rough print, not fusing completely

Laserjet 4600 exhibits rough and or unfused print on left or right edge for  1″ to 1.5″ into page.  This can be caused by the pressure release levers on the fuser being out of position. These levers, used to help remove fuser jams, should be in the position which applies pressure to the media as it passes between the rollers. The lever is on the opposite side of the fuser as you face the printer from the edge that is not fusing.  Left side not fusing, check right lever. These are the levers, not the thumb screws securing the fuser.

HP Fuser Assemblies

HP Laser Printer Fusers

A critical component of a laser printer is the fuser or fixing assembly. This assembly is used to “fuse” the toner to the media. Toner is made up of a plastic, pigment, waxes, and iron compound, which will melt when heated by the fuser assembly. After the toner is deposited to the media, it passes through the fuser assembly and the toner is melted into the fibers of the media. The fuser provides not only the high temperature via the upper temperature roller, but also pressure as the lower rubber type roller presses the media against the temperature roller. As the speed of printers increases, so does the speed of the fuser assembly and the associated components. Also the temperature must be uniform and transfer heat rapidly to the media since it passed through the fuser assembly more quickly.

Early laser printers used a halogen lamp suspended in a hollow aluminum tube as the heat roller. The outer surface of the tube was coated with a teflon compound to facilitate release of the media which tends to stick to the surface. You can see how the chemistry of the toner is very important and not all toner is the same.

Most current laser printer fuser assemblies use a plastic film roller sleeve which rotates around a solid state thin film ceramic heating element. This configuration offers greater efficiency in heat transfer and rapid heating of the fuser assembly roller by the ceramic element. With this configuration you can experience almost instant on printing. Attempts to decrease costs have resulted in easier shredding of the fuser roller and alternatives are being developed.

As with any mechanical part, the fuser assembly is subject to wear and is the main component of a laser printer maintenance kit. Data has shown a standard recomended replacement interval for office size printers and thus the “Perform Printer Maintenance” message that appears on the display at a pre determined page count. You may also have to replace the fuser assembly if the roller becomes damaged by a jam or jam removal, labels peeling and sticking to the coated surface and damaging the coating or mechanical failure of a gear or roller.

HP LaserJet 4250 and 4350 Maintenance Kits

HP Maintenance Kits for the HP LaserJet 4250 and 4350

You should replace certain parts when the PERFORM PRINTER MAINTENANCE message appears on your printers control panel display. This will help ensure that your printer maintains optimum performance.
The maintenance message will appear every 200,000 pages. The message can be temporarily cleared for approximately 10,000 pages by using the CLEAR MAINTENANCE MESSAGE item on the Resets submenu. To check the number of
pages the printer has printed since new maintenance-kit components were installed, print either a configuration page or a supplies status page.
To print a supplies status page at the control panel

1. Press (SELECT button) to open the menus.
2. Use (UP button) or (DOWN button) to scroll to INFORMATION, and then press
(SELECT button).
3. Use (UP button) or (DOWN button) to scroll to PRINT SUPPLIES STATUS PAGE,
and then press (SELECT button).

To order the printer maintenance kit online follow this link hpmaintenancekits.com
The kit includes:
A new or remanufactured fuser, your choice – reduce costs with a remanufactured assembly
New rollers – a transfer roller, pickup, and feed rollers
Installation instructions
NOTE The printer maintenance kit is a consumable item and is not covered under the original printer warranty or under most extended warranties.
After a maintenance kit is installed, the maintenance-kit counter must be reset.

To reset the maintenance-kit counter
1. Turn the printer power off and then on.
2. When XXX appears on the control-panel display, press and hold down (SELECT
button). Continue holding down (SELECT button) until all three printer control panel
lights flash once, and then stay on. This might take up to 10 seconds.
3. Release (SELECT button) and press (UP button) to scroll to NEW MAINTENANCE KIT.
4. Press (SELECT button) to reset the maintenance-kit counter.
NOTE Perform this procedure only after a maintenance kit has been installed. Do not use this procedure to temporarily clear the PERFORM PRINTER MAINTENANCE message.

Laser printer page defects – Common causes

Defects on the printed output from HP laser printers can be traced to their cause
by use of a tool called a repetitive defect ruler. If a roller in the paper path has a
defect the defect will occur 2 or more times on a page printed in the portrait mode.
For example, a nick in the image drum of an HP LaserJet 4250 or HP LaserJet 4350 printer will
occur every 3.75 inches, the circumference of the drum. The use of this defect ruler
can help you decide if you need to replace the toner cartridge or the problem is in
the fuser assembly and it’s time for a new fuser assembly or maintenance kit. With
this info you may be able to save a service call and know what needs to be done.
A good source of information to help is at All Laser Service.

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