HP 4 Plus Manual

							Formatter Cage Removal
NoteYou may wisht to remove the metal cover (on the
lower right side) and the power supply for easier
access to the Formatter Cage screws.
1Remove the Right Side Cover and the Top Cover.
2LaserJet 4 and 5:  Remove the (7) screws (6 screws in the LJ
5) shown in Figure 6-24a.  (2) screws are on the right rear of
the printer, (1) screw is under the lower front of the Formatter
Cage (except LJ 5). 
LaserJet 4 Plus:  Remove the (3) screws shown in Figure
6-24b (one screw is located behind the SIMM door), and the (2)
screws on the right rear of the printer (shown in Figure 6-24c).
3Remove the Rear Door Support Strap.
4Slide the Formatter Cage straight out the right side of the
printer, being careful not to damage the Formatter/DC
Controller pin connectors.
(continued on next page)
Figure 6-24a Formatter Cage Screws (Right Side View - LaserJet 4 and 5)
Removal and Replacement  6-27 
						

							Figure 6-24b Formatter Cage Screws (Right Side View -LaserJet 4 Plus)
Figure 6-24c Formatter Cage Screws (Rear View - LaserJet 4Plus)
6-28 Removal and Replacement 
						

							Formatter PCA Removal 
CautionThe Formatter PCA is very sensitive to Electro-
static Discharge (ESD) damage. Observe proper
ESD procedures when servicing the printer.
NoteBefore removing the old Formatter PCA, print a
05 SELF TEST
 to check the current printer page
count, if possible.  If a self test is not possible,
enter the Service Mode, if possible, to display the
page count (see  “Service Mode ” in Chapter 3).
Remove the Formatter Cage from the printer before beginning
the Formatter PCA removal procedure. After the Formatter Cage
is removed, remove the Formatter PCA as detailed on the
following pages.
(continued on next page)
Removal and Replacement  6-29 
						

							LaserJet 4 Formatter PCA:
1Remove any MIO or SIMM modules from the Formatter
Assembly.
2Remove the (2) black screws from the side of the Formatter
Cage (see Figure 6-25a, callout 1).  
3Remove the MIO Connector Support Bracket (see Figure
6-25a, callout  2).
4Remove the (2) Formatter PCA mounting screws (see
Figure 6-25a callout  3).
(continued on next page)
Figure 6-25a Formatter Cover and PCA Mounting Screws (LaserJet 4)
6-30 Removal and Replacement 
						

							5Remove the (4) Interface Connector Support Screws from the
rear of the Formatter Cover. The RS-232 connector is held
with 5mm hex-head cap screws (see Figure 6-25b, callout 1).
The parallel connector (see Figure 6-25b, callout  2.) is held in
place with Phillips screws.
6Remove the Formatter PCA.
Note When replacing the Formatter Assembly be sure
to reinstall all SIMM modules and MIO cards.  Be
sure to reset the page count and the Cold Reset
paper size after replacing the Formatter.
(continued on next page)
Figure 6-25b Interface Connector Support Screws (LaserJet 4)
Removal and Replacement  6-31 
						

							LaserJet 4 Plus and 5 Formatter PCA
1Remove any MIO or SIMM modules from the Formatter
Assembly.
2Remove the MIO Connector Support Bracket (see
Figure 6-25a, callout 2).
3Remove the (4) I/O screws (see Figure 6-26 callout  1).
4Remove the (2) Formatter PCA mounting screws (see
Figure 6-26 callout  2).
Note When replacing the Formatter Assembly be sure
to re-install all SIMM modules and MIO cards.
Be sure to reset the page count and the Cold
Reset paper size after replacing the Formatter.
Figure 1-26 Interface Connector Support Screws (LaserJet 4
Plus and 5)
6-32 Removal and Replacement 
						

							DC Controller Removal
NoteNote the cable routing before beginning this
disassembly procedure.  Be careful not to damage
the cables during re-assembly.
1Remove the Right Side and the Top Cover Assemblies.
2Remove the Formatter Cage Assembly.
3Remove the 6-wire connector from the Power Supply.
4Remove the plastic DC Controller cover (LaserJet 4 Plus).
5Remove the DC Controller connectors (see Figure 6-27a or
6-27b, callout 1). 
6Release the DC Controller from its retaining clips (2) and
remove the DC Controller (see Figure 6-27a or 6-27b,
callout  2).
Figure 1-27a DC Controller Connectors/Retaining Clips
(LaserJet 4)
6-33 Removal and Replacement 
						

							Figure 1-27b DC Controller Connectors/Retaining Clips(LaserJet 4 Plus/5)
6-34 Removal and Replacement 
						

							DC Controller Installation     
CautionWhen reinstalling the DC Controller PCA it is
extremely important that 
all cables be properly
routed.   If cables are not routed properly, it is
difficult to reinstall the Formatter Cage and cable
damage may result.
When replacing the DC Controller, be sure to set the leading edge
adjustment as shown in the following procedure.
Note The Leading Edge Adjustment is set at the
factory and is 
not required as a maintenance
procedure. The Leading Edge Adjustment should
be done only when the DC Controller is replaced.
The following procedure is performed with the Formatter
Assembly removed.
To set the Leading Edge Registration:
1Install the new DC Controller in the reverse order of the
removal.
2Run a test print to check the leading edge adjustment (as
shown in Figure 6-28.
3Use VR202 (LaserJet 4) or VR201 (LaserJet 4 Plus and 5) (see
Figure 6-29) to adjust the leading edge registration to the
dimension shown in Figure 6-28 (a=2mm).
4Make several test prints ( 15 ENGINE TEST as shown in
Figures 3-5 and 3-6) and check the adjustment. Repeat the
above steps until the adjustment is correct.
6-35 Removal and Replacement 
						

							Figure 1-28 Leading Edge Registration AdjustmentDimensions
Figure 1-29 VR202 Settings (LaserJet 4 shown)
6-36 Removal and Replacement