Light Print – HP Laserjet Printer 4, 4+, 5, 5N Laser Scanner Repair

 

Light Print – HP Laserjet  Printer 4, 4+, 5, 5N Laser Scanner Repair

Light print on the HP laserjet  4, 4+, 5, and 5N printer models has been an issue for quite some time. The problem is usually pretty gradual so most customers don’t even realize how  much their machines print quality has declined until it gets a proper cleaning.  The light print  problem typically  starts on the left side and as the machine ages like these the light print  eventually goes throughout the whole page.    Inside the laser scanner assembly is several mirrors and lens. On top the laser motor is a polygon mirror.   As the mirrors on top of the motor  rotate, the sides of the mirrors tend to attract more debris and dust. When dust and debris builds up on the mirrors the  laser that writes  to the drum fails to produce a good image  .  In this article I’m going to discuss  how to clean the  laser scanner  so you can get your HP laserjet  4, 4+, 5, and 5N printers print quality restored and your light print issue a thing of the past.

Tips for Cleaning Your HP Laserjet  HP Laserjet  4, 4+, 5, and 5N Printer

In most cases you can clean the inside of your HP laserjet  4, 4+, 5, and 5N without the use of canned air. Generally, these printers stay rather clean inside and most the dirt and dust can be cleaned out with just a dry or slightly damp lint free cloth avoiding the transfer roller. If you decide to use canned air in the machine make sure you cover the top of the printer cavity first. Inside the printer cavity is a slot for the opening of the laser scanner unit. The front mirror inside the unit sits just above the opening. If you use canned air toner and dust can get deposited on the mirror and result in light print where you previously didn’t have any.

Troubleshooting light print in a HP Laserjet  HP Laserjet  4, 4+, 5, and 5N Printer

I added more detail to the troubleshooting tips. Instead of making this article extremely long I decided to create a new article and link to it. Below is the updated article for further assistance on your light print issues.
Troubleshooting Light or Faded Print – HP Laserjet Printers

Laser Scanner Cleaning Procedure for Light Print on a HP Laserjet  4, 4+, 5, and 5N Printer

Right Side Cover Removal
LJ 4/4 Plus
1. Open the Top Cover and release the Right Side Cover by pressing at the points
2. Fold the cover away from the printer to release the bottom supports and lift the door off of the printer frame.

LJ 5
1. Open the Top Cover and loosen the retaining screw on the right side cover located at the upper right rear of the printer.
2. Slide the right side cover back and fold the cover away from the printer to release the bottom supports.

Top Cover Removal
1. Open the Top Cover.
2. Remove the Right Side Cover.
3. Open the Rear Door.
4. Remove the (3) screws. 2 in rear top. These like to break becuase  of the age of the plastic. If they dont break during removal do not over tighten when reinstalling. 1 screw in front under the top cover door just down from the control panel.
5. Release the (2) latch points with a flat screwdriver while, lifting the Top Cover. Latches are located in the very front of the machine right under where the lid opens.
6. Carefully lift the top cover to access the Control Panel cable.
7. Disconnect the Control Panel Ribbon Cable and remove the top cover

Output Assembly Removal
1. Remove the Right Side Cover, the Top Cover, and the Left side Cover.
Note : The service manual says to remove the left side cover. I did not include it in the instructions becuase you shouldn’t have to remove it for this procedure.
2. Release the grounding strap from the left side of the frame.
3. Rotate the top of the Output Assembly toward the front of the printer while releasing the two retaining latches until the locating tabs are free. Slide the assembly to the rear and lift it out of the printer.

Scanner Assembly Removal
1. Remove the Right Side Cover, Top Cover, Left Side Cover, and the Output Assembly.
2. Remove all cables from the Scanner retaining clips.
3. Remove the (3) connectors
Note: Be careful not to flex the Laser PCA when removing or installing the cables. The Laser PCA can be damaged easily
4. Remove the (4) screws from the Scanner Assembly.
5. Remove the Scanner Assembly.

I gave the instructions to remove the laser scanner unit but really you shouldn’t have to remove it. I believe 1 screw and 4 clips hold the top cover on. I listed the uninstall procedure because some people find the clips easier to remove with the unit out.

Cleaning the Laser Scanner Unit on the HP Laserjet  4, 4+, 5, and 5N Printer

By now the optics inside the laser scanner unit in these machine most likely all have a layer of dust on them so both the mirrors and lenses should be cleaned. Use a dry Q-tip to clean the mirrors and lenses. If you see any dirt build up on the Q-tip get a new one before proceeding to the next mirror or lens.  All I can say here is to be as gentle as possible and take your time. This is one job where you want to make sure you do it right the first time so you don’t have to repeat.    The mirrors and lenses  can get scratched easily, especially the motor mirrors on top the motor. Again, this is not a race so take your time and replace the Q-tip as often as needed. Using one side per mirror is fine.  If you scratch the motor mirrors you can have permanent  damage that will require replacement of the whole laser scanner assembly. Look at the motor mirrors at different angles so you can see the build up of dust on the sides and make sure you eliminate it as much as possible.

HP Laerjet 4, 4+, 5, 5N laser scanner cleaning

Conclusion about Light Print in the HP Laserjet  4, 4+, 5, and 5N Printer Repair

The light print problem in the HP laserjet  4, 4+, 5, and 5N  has been around for quite some time by now. Hopefully, this article will help you take care of your light print problems and will guide you through the removal of the laser scanner cover and and clean out the optics inside and restore your print quality to what it should be.

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