HP LaserJet 4 and 4M – How to reset – Service Mode – Working details of photosensitive drum
Applicable to: HP LaserJet 4/4M (C2001A/C2021A) - HP LaserJet 4 Plus/4M Plus (C2037A/C2039A) - HP LaserJet 5/5M/5N (C3916A/C3917A/C3952A)
Reset Menu
Use Reset Menu function with caution. It can result in loss of buffered page data or printer configuration data. Reset Menu is activated by holding down both [Shift] and [Menu] for up to 10 seconds until RESET=MENU* appears. Use [+] or [-] to cycle through items and [Enter] to select the item. The reset is executed by pressing [On Line].
Use Reset Menu function with caution. It can result in loss of buffered page data or printer configuration data. Reset Menu is activated by holding down both [Shift] and [Menu] for up to 10 seconds until RESET=MENU* appears. Use [+] or [-] to cycle through items and [Enter] to select the item. The reset is executed by pressing [On Line].
To
initiate the Service Mode
Hold
down the [ON LINE], [FORM FEED], and [ENTER] keys while powering ON the
printer, until the ON LINE and FORM FEED Indicators are both illuminated and the
Display Window is blank. (If the Display Window reads 05 SELF TEST at this
point, the keys were released too soon. Repeat this step until successful.)
After
several seconds, the [ON LINE] and [FORM FEED] lights turn OFF. (The printer
may display 02 WARMING UP if it has not warmed up completely.) ss the [FORM
FEED] key, then the [ENTER] key. The message SERVICE MODE is displayed briefly,
then the printer automatically begins a 05 SELF TEST.
After
the printer has warmed up and passed the self test, SERVICE MODE is displayed.
To
exit the Service Mode press the [ON LINE] key.
Setting the Cold Reset Default
The default paper size
outside of the U.S. is typically A4. Therefore, when replacing
Formatters where the desired default is A4, the Customization Variable
must be set to A4. This prevents the Cold Reset procedure from resetting
the paper size to Letter. To set the Customization Variable
1 Enter the Service Mode as described previously.
2 Press the [Menu] key to display SERVICE MENU.
3 Press the [Item] key to display CR PAPER=LETTER
4 Press the [+/-] key to toggle between Letter and A4 paper.
5 Press the [Enter] key to save your selection.
6 Press [On Line] to exit the Service Mode.
Cold Reset
The Cold Reset feature of
the printers allows the printer to be returned instantly to the factory
default configuration settings. This feature is valuable because the
the Dynamic I/O and PJL features of the printer enable any user
connected to any I/O to access and change the default configuration as
applications require. When setting up the printer in a new location, or
when troubleshooting printer problems, always perform the Cold Reset
before entering the selected user defaults. A Cold Reset can not reset
the page count, cold reset tray size, or display language settings. If
the Control Panel is locked, a Cold Reset will disable the lock and
return the printer to the factory defaults. Inform the system
administrator of all Cold Resets.
A Cold Reset is performed as follows:
1 Turn OFF the printer.
2 Hold the [On-Line] (or Go for the LJ5) key down while powering ON the printer.
3 The message COLD RESET is displayed. The COLD RESET does not take effect until the 00 READY message is displayed.
4 When the 00 READY
message is displayed, the default settings have been returned to the
factory defaults and the printer is ready to accept new settings.
Install Printer Drivers and Utilities
Printer drivers are specialized programs designed to allow specific software applications to function with the HP LaserJet printers. Printer utilities include such things as the HP Explorer program modules, which enhance the usability of the printer and provide convenient access to printer features outside of specific software applications.
Printer drivers are specialized programs designed to allow specific software applications to function with the HP LaserJet printers. Printer utilities include such things as the HP Explorer program modules, which enhance the usability of the printer and provide convenient access to printer features outside of specific software applications.
How
to Obtain Printer Drivers
First, check the software’s printer selection feature to see if the printer is listed among the available printers. If it is not, run the software’s SETUP or INSTALL program to install a “printer driver” or “printer file” for the printer.
Here are some ways to obtain printer drivers and Software Application Notes for HP LaserJet printers:
• Check the Printing Software package to see if it includes a driver for your software.
• Order an updated driver from the software vendor.
• Call Hewlett-Packard at 970-339-7009.
• Obtain a driver request form by fax through HP FIRST (call 1-800-333-1917) U.S. only.
• Download a driver through CompuServe’s HP Forum.
First, check the software’s printer selection feature to see if the printer is listed among the available printers. If it is not, run the software’s SETUP or INSTALL program to install a “printer driver” or “printer file” for the printer.
Here are some ways to obtain printer drivers and Software Application Notes for HP LaserJet printers:
• Check the Printing Software package to see if it includes a driver for your software.
• Order an updated driver from the software vendor.
• Call Hewlett-Packard at 970-339-7009.
• Obtain a driver request form by fax through HP FIRST (call 1-800-333-1917) U.S. only.
• Download a driver through CompuServe’s HP Forum.
To sign up for CompuServe,
call 1-800-524-3388.
[While
waiting for a specific HP LaserJet printer driver, you can substitute a similar
printer driver (such as a driver for the HP LaserJet III, IIIP, or 4 printer).
These substitute drivers will allow you to use the printer, but they do not support all of the printer’s features.]
Troubleshooting a SIMM Board. Service / Error Messages
One of two messages can be generated when your printer is checking its SIMM internal memory.
61.X SERVICE
where X = 1, 2, 3, or 4
This error indicates a
SIMM parity error. The x indicates which SIMM slot generated the error.
If these messages appear first, check the HP part number to make sure
you have the right SIMM board.
62.X ERROR
where X = 0, 1, 2, 3, 4, or 5
This error indicates your printer identified a problem while checking memory.
If x=0, the problem is in internal Read Only Memory (ROM) on the Formatter.
If x = 1, 2, 3, or 4, the problem is in SIMM slot 1, 2, 3, or 4.
If x = 5, the problem is in an external cartridge installed in the printer.
Removing and Replacing the Transfer Roller
The Transfer Roller is the
black sponge-rubber roller located inside the printer just to the front
of the black plastic Paper Feed Guide. To remove and replace the
Transfer Roller, follow these steps. [Do not handle the new Transfer
Roller unnecessarily. Oils will build up on the roller and cause print
quality problems.]
Removing the Transfer Roller
1 Turn OFF and unplug the printer.
2 Open the printer’s top cover.
3 Remove the Toner Cartridge.
4 Use the hook inside the top cover to remove the Transfer Roller as follows.
Hook the left side of the chrome rod beside the sponge roller, and lift the roller out.
5 Discard the used roller.
Replacing the Transfer Roller
1 Slide the right end of the new roller (the end without the gear), onto the right slot. Press the rod into the slot.
2 Lower the gear end of the roller into place.
3 Install the toner cartridge.
4 Replace the hook tool.
5 Close the top cover.
6 Plug in the power cord and switch the printer ON.
Photosensitive Drum – working principle
Working principle of Photosensitive Drum is similar to all deskjet printers, irrespective of its brand
The
photosensitive drum is the “heart” of the Image Formation System. The
special
properties of this drum allow an image to be formed on the drum’s
surface and
then transferred to paper. The drum is an extruded aluminum cylinder.
The
outside of the cylinder is coated with a layer of
organic-photo-conductive material (OPC) which is non-toxic. The aluminum
base of the photosensitive drum
is electrically connected to ground potential.
Drum Sensitivity
The OPC material has
properties similar to a photo-resistor. It becomes electrically
conductive when exposed to light. When the photosensitive drum is
exposed to light, the negative charges deposited on it are conducted to
the ground potential of the drum’s base. Areas not exposed to light
remain nonconductive and maintain their negative charge. [Do not expose
the Toner Cartridge to any bright light source. Too much light
permanently damages the drum]
Cleaning Stage
During the cleaning stage
of the image formation process, the drum’s surface is physically
cleaned, preparing it to hold an image. During printing, the drum is
rotating constantly making several complete rotations per printed page.
Before forming the image for a given section of print, a cleaning blade
removes toner from the previous rotation of the drum. The excess toner
is stored in the toner cartridge where it is prevented from being used
in later print jobs.
Conditioning Stage
After the drum is physically cleaned, it must be conditioned. This process consists of applying a uniform negative charge on the surface of the drum with the primary charging roller, located in the toner cartridge. The primary charging roller is coated with conductive rubber with an AC bias applied to erase any residual charges and maintain a constant drum surface potential. In addition, a negative DC bias is applied by the charging roller to create a uniform negative potential on the drum’s surface. The amount of DC voltage is modified by the print density setting from the Control Panel.
After the drum is physically cleaned, it must be conditioned. This process consists of applying a uniform negative charge on the surface of the drum with the primary charging roller, located in the toner cartridge. The primary charging roller is coated with conductive rubber with an AC bias applied to erase any residual charges and maintain a constant drum surface potential. In addition, a negative DC bias is applied by the charging roller to create a uniform negative potential on the drum’s surface. The amount of DC voltage is modified by the print density setting from the Control Panel.
Writing Stage
At the writing station,
the laser beam is used to discharge the drum’s negative potential by
focusing laser light onto areas of the photosensitive drum. This creates
a latent electrostatic image, which later is developed into a visible
image. Laser light is produced by a small modulated laser diode. The
beam created by the diode shines onto a rotating polygonal mirror. As
the mirror rotates, the beam reflects off the mirror and sweeps the page
from left to right. (see Figure). A set of lenses and mirrors focuses
the horizontal sweeping beam through the laser beam access slot in the
rear of the toner
cartridge, and onto the
photosensitive drum. Because the beam is sweeping the entire length of
the drum and the drum is rotating, the entire circumference of the drum
can be covered. The speed of the
scanner motor (which turns the scanning mirror) and the speed of the
main motor (which turns the drum) are synchronized, and each successive
sweep of the beam is offset 1/600th of an inch. The beam can be turned
on and off to place a dot of light every 1/600th of an inch in the
horizontal direction. This is how the printer achieves its 600 x 600
DPI resolution.
At the beginning of each
sweep (before the beam reaches the drum), the beam is reflected off the
beam detect mirror. The momentary pulse of light is sent to the DC
Controller, where it is converted to an electrical signal used to
synchronize the output of data (VDO) for one sweep (scan line). This
pulse, referred to as the Beam Detect signal (BD), is used to diagnose
problems with the laser diode or scanner motor also. After the writing
station, the drum surface has an invisible (latent) electrostatic image.
Portions of the drum not exposed to the laser are still at the uniform
negative potential (placed there by the primary charging roller), but
those portions exposed to light have been discharged to ground, to form
the latent electrostatic image.
Developing Stage
The developing station
develops the latent electrostatic image into a visible image on the
drum. The developing unit consists of a metallic cylinder that rotates
around a fixed magnetic core inside the toner cavity. Toner is a powdery
substance made of black plastic resin bound to iron particles, which is
attracted to the magnetic core of the cylinder. A rubber blade
“brushes” the toner on the developing cylinder to a uniform thickness.
The toner particles obtain a negative surface charge by rubbing against
the developing cylinder which is connected to a negative DC supply. The
negatively charged toner is attracted to the discharged (grounded)
areas of the drum exposed to laser light, and repelled from the
negatively charged (non-exposed) areas. An AC potential is applied to
the developing cylinder to decrease the attraction between the toner and
the magnetic core of the cylinder, and to increase the repelling action
of toner against the areas of the drum not exposed to laser light. This
AC potential improves density and contrast.
The DC bias of the
developing cylinder is adjusted to change the force of attraction
between the toner and drum by changing the print density setting from
the control panel. A change in DC bias causes
either more or less toner to be attracted to the drum, which in turn
either increases or decreases the print density. The print density
variation is approximately ±10%. Both the primary and developer DC bias
voltages are changed in response to the density setting.
Transferring Stage
At the transferring
station, the toner image on the drum’s surface is transferred to the
paper. A positive charge applied to the back of the paper by the
transfer roller causes the negatively charged toner on the drum’s
surface to be attracted to the page. The small radius of the drum and
the stiffness of the paper peel the paper away from the drum. The static
charge eliminator also helps separate the paper from the drum. The
static charge eliminator weakens the attractive forces between the
negatively charged drum surface and the positively charged paper.
Without this help, thin paper can wrap around the drum. After
separation, the paper moves to the fusing station and the drum rotates
to the cleaning and conditioning stations.
Fusing Stage
