HP 4 Plus Manual

1
2
3
4
Figure 7-13 Major Assembly and Connector Locations (3 of 3)
NumberPart
1 Power Supply Assembly
2 Envelope Feeder Main Motor (M4)
3 Lower Cassette Drive PCA
4 Lower Cassette Main Motor (M3)
Table 7-33
Troubleshooting 7-61 

Figure 7-14 Switch Locations 
NumberPart
SW101 AC Input ON/OFF Switch (Power Supply Assembly)
SW 601 Top Cover Open Sensing Switch
SW602 TEST PRINT Switch
SW603 PC (Tray 2) Tray Size Switches
SW604
SW605
Table 7-34
7-62 Troubleshooting 

Figure 7-15 Optional 500 Sheet Lower Cassette
NumberPart
SW851 Optional 500 Sheet Paper Feeder Paper Tray (Tray 3)
Size Switches
SW852
SW853
Table 7-35
Troubleshooting 7-63 

5VR202
J206
J203 J204 J205
61 1
8 1
1
7
1 2
1
3 1J202
J201
13
1
3 J212 CP202
16TB201
CP201J211
4 110 1
J210 3 1
J209 4 1
3 1 25 26
J213
J208
J207
Figure 7-16 DC Controller PCA Layout—LaserJet 4/4M
Number
Part
J201 Paper Control PCA
J205 Scanner/Beam Detect
J206 Laser Drive PCA
J207 Formatter PCA
J208 Deliver/Exit Sensor PS3
J210 Interconnect PCA
J209 Cooling Fan
J211 Main Motor
J212 Power Supply/Fuser Drive
VR202 Registration Adjustment
TB201 DC Voltages (from Power Supply)
Table 7-36
7-64 Troubleshooting 

5J204 15 1
1
9 2
1
J206 J205
VR201
1
13 31
17
J201
J212 31
J215
TB201 6 1 J214
10 1J213 31
J211 3
J210 1
8 1
1
7
J209J208
J207
31 32
Figure 7-17 DC Controller PCA Layout —
LaserJet 4 Plus/5
NumberPart
J201 Paper Control PCA
J208 Scanner/Beam Detect
J209 Laser Drive PCA
J207 Formatter PCA
J210 Deliver/Exit Sensor PS3
J213 Interconnect PCA
J211 Cooling Fan
J214 Main Motor
J215 Power Supply/Fuser Drive
VR201 Registration Adjustment
TB201 DC Voltages (from Power Supply)
J206 Control Panel
Table 7-37...

TB403 TB404TB405 TB406VR401
J402
3
1
J401
5 1A
B
A
B
TB402
TB401
Figure 7-18 High Voltage PCA Layout
Number Part
J401 High Voltage PS Connection To DC Controller PCA via Interconnect PCA
TB401 Transfer Roller Contact
TB402 Drum Ground Contact
TB403 Toner Low/EP Toner Cartridge-in-Place Contact
TB404 GND
TB405 Developer Roller Contact
TB406 Charge Roller Contact
VR401 Factory Adjustment Only
Table 7-38
7-66 Troubleshooting 

Repetitive Defect Template  
Repetitive print defects usually are associated with a specific
roller within the printer, or the Toner Cartridge.  The following
templates are provided to help quickly isolate the cause of
repetitive print defects.  Align the first occurrence of the defect
with the top of the “ruler” , and measure to the next occurrence of
the defect to determine the roller in question.  When you are
certain that your defect pattern matches the pattern of the
template, replace the indicated...

Figure 7-20 Main Wiring Diagram (LJ 4+/5 only)
7-68 Troubleshooting 

Voltage Test Points  
The operating voltages of the printer can be verified by:
1Listening for the exhaust fan. A rotating fan indicates that the
+5 VDC and +24A VDC voltages are present. (The fan runs on
+24A VDC.  The +5 VDC enables the +24A VDC.)
2Listen for the Main Motor.  If the Main Motor runs, the +24B
VDC is enabled, therefore +24A VDC must be present.  
Measuring the DC Voltage Levels 
The DC voltage levels can be measured directly on the DC
Controller TB 201. TB 201 connects the DC Controller...

7-70 Troubleshooting