Light Print or no Black on the Page

HP Color LaserJet 3500 and 3700 Series Printers - This can be due to several reasons already listed in the Service manual. A new "cause" for this has been discovered: faulty K-Clutch in the Image Drive Assembly

The following are listed in the service manual as possible causes:
1. Formatter
2. Defective laser shutter
3. Poor developing bias contacts
4. Defective cartridge (primary charging roller)
5. Laser/scanner unit is defective
6. High-voltage PCB is defective
7. DC Controller PCB is defective

It has been discovered that a faulty K-clutch (p/n: RK2-0248-000CN) in the Image Drive Assembly could also cause light or no black print. Figure1

Faded print or missing black toner

Follow the trouble-shooting causes from the service manual (listed in tables below), and if these do not work, check to see if the K-clutch (p/n: RK2-0248-000CN) is faulty. Replace the clutch if it is.

Light Print

Causes for light images

The image density is not properly adjusted.

Calibrate the printer. (See instructions below.)

Deteriorated transfer unit.

If the transfer unit is at the end of its life or its surface is deteriorated, replace the transfer unit.

Deformed/Deteriorated secondary transfer charging roller.

Replace the secondary transfer charging roller.

Defective high-voltage PCB.

Replace the high-voltage PCB.

Defective DC controller PCB.

Replace the DC controller PCB.

Calibrate Now

Use the following procedure to calibrate the printer whenever you replace the DC controller, the formatter, the color misregistration sensor (PS12), the transfer unit, or the laser/scanner.

Press to enter the MENUS.
Press to highlight configure device.
Press to select configure device.
Press to highlight PRINT quality.
Press to select PRINT quality.
Press to highlight CALIBRATE NOW.
Press to select CALIBRATE NOW.
Wait for the printer to calibrate.

Light color

Print out a solid filled image of the problem (light) color using an external device. In the course of printing, turn the printer off and take the problem color?s cartridge out. Manually open the cartridge shutter. If the toner image on the photosensitive drum is not fully transferred to the transfer unit, go to step B in the table below. If the toner image on the drum before transfer is light, go to step A.

Causes for one color printing light

Poor developing bias contacts.

Check the developing bias contacts to the high-voltage PCB. Clean contacts, if dirty. Replace defective parts if contacts are deformed or damaged.

Deteriorated cartridge (photosensitive drum).

Replace the cartridge of the problem (light) color.

Defective high-voltage PCB.

Replace the high-voltage PCB.

Defective DC controller PCB.

Replace the DC controller PCB.

Poor primary transfer bias contacts.

On the transfer unit, check the primary transfer bias contacts with the highvoltage PCB. Clean contacts, if dirty. Replace defective parts if contacts are deformed or damaged.

Deformed/Deteriorated primary transfer charging roller.

Replace the transfer unit.

© 2005 Hewlett-Packard