HP Laserjet 4 Manual

51 ERROR Message  
The 51 ERROR, and the 41.2 ERROR are caused by Beam Detect
failures. If the beam detect signal is lost for more than 2 seconds
the error is posted as a 51 ERROR. The 41.2 ERROR can be cleared
by pressing [Continue] (or Go). The 51 ERROR may be cleared by
power cycling the printer.
Figure 7-6 Fuser Assembly Connector
Checks Action
1. Are all connectors on the DC
Controller properly seated?Inspect connectors and wiring. Reseat or
replace cables if necessary.
2. Is the Laser/Scanner...

52 ERROR Scanner Malfunction  
The scanner motor is a flat, brushless, DC motor. Motor operation
is completely controlled by the DC Controller.  
The scanner motor is enabled when the printer is powered-up
(during the printer’s power-on self test), or whenever the PRINT
command is received by the Formatter PCA.  The scanner motor
makes a distinctive sound when starting.  The sound can be
described as a “variable pitch whirring” sound.  Listen for the
sound of the scanner motor when troubleshooting the 52...

57 (or 57.1) SERVICE Message (Main Motor
Fa i l u r e )   
The 57 SERVICE indicates that the DC Controller PCA detected a
general motor failure. The Main Motor drives all moving
components in the printing process. The Main Motor is a 4-phase,
DC servo motor controlled by the DC Controller PCA. 
The formatter detects a Main Motor failure when:
•The Main Motor does not come up to speed within one second
of receiving drive voltage.
•The Main Motor deviates from the correct speed for one second
after...

58 (or 57.2) SERVICE (Fan Failure)     
The 58 SERVICE indicates that the DC Controller detected a
failure in the Exhaust Fan (FM1) in  the printer or the optional
duplexer.  When troubleshooting this problem, perform the
following steps in the order given.
1Check that the fan is mounted correctly in its shroud.
2Check that the fan blades are not blocked.
3Check that the Cooling Fan connector is firmly seated on the
DC Controller (see Figure 7-16 or Figure 7-17 for location).
If the above checks are...

Image Defect Summary               
The quality of the printer’s output is subject to the judgment of
the user.  This section of the manual helps you define print
quality defects, and understand what factors affect print quality.
The print samples shown in the following figures illustrate some
print quality defects.  Keep copies of print quality defects
encountered in the field with an explanation of their causes for
future reference.
The image defects listed below are covered in the following tables....

Figure 7-7 Image Defect Summary
7-36 Troubleshooting 

Figure 7-8 Image Defect Summary
Troubleshooting 7-37 

Possible Cause Action
The HVPS connections are dirty. Clean the HVPS terminals (see Figure
7-18 for layout).
The HVPS is installed improperly. If the
HVPS has been removed and replaced,
it may not be seated properly.Remove the HVPS, and check the
connectors for damage. Reseat the
HVPS, being certain to fully seat the
connectors.
Bad Primary Charging Roller. Replace the Toner Cartridge.
The HVPS is defective. Replace the HVPS.
DC Controller PCA. The laser drive
circuitry is damaged so that the laser is...

Possible Cause Action
Paper. The surface of the paper may be
too smooth for the pickup roller to move
the paper through the paper path.Change paper. Try a brand of paper
known to be good.
Worn Pickup Roller and Separation Pad. If the Paper Pickup Roller, or the
Separation Pad are sufficiently worn, the
leading edge of the paper may not reach
the registration assembly in time.
Replace the Pickup Roller and
Separation Pad together.
PS1 faulty. If the Input/Registration
sensor (PS1) is broken, it can not...

 
Possible Cause Action
No toner available for print. Shake/replace the EP Toner Cartridge.
Laser shutter may be blocking the beam Ensure that the mechanism that lifts the
shutter is functional, for example, the
shutter doesn’t stick in its travel, and is
lifted evenly. 
Table 7-15Right-Hand Image Missing 
Possible Cause Action
Small voids on black, or near-black
printed images may be caused by
imbedded toner on the
electro-photographic drum. Cartridges
that are run for long periods of time in
high...