HP LaserJet 4 Service Manual - Page 278

Table 7-28 White or Blank Pages Possible Cause Action Defective laser shutter. Check the laser shutter for free operation when inserting the EP Toner Cartridge. EP Cartridge Support damaged, improperly positioned, or missing. Refer to item 4 in Figure 8-4a. Guide must be installed properly above the EP Cartridge, between the laser shutter opening and the fuser stop plate. Toner Cartridge. No toner is available for Remove sealing tape or replace the print. Toner Cartridge. No Transfer Roller voltage. Without transfer charge roller voltage, toner cannot be attracted from the surface of the drum to the paper. Perform the "Half Self Test Functional Check" which follows to check all other electro-photographic processes. No Developing Bias. With no Developing Refer to "High Voltage System Checks." Bias charge, toner is not attracted to the drum. No drum ground path. With no ground path the drum cannot discharge. The negative charge on the drum repels toner, and leaves a white page. Refer to "High Voltage System Checks." Bad Laser Scanning Cable Assembly. Low-level signals exchanged between the Laser/Scanning Assembly, and the DC Controller may be affecting laser output. Replace the Laser/Scanning Cable Assembly. 7-48 Troubleshooting