HP 2420 Service Manual - Page 78

Timing Sequence of operation The microprocessor on the dc controller controls the printer operation sequences. Table 5-1. Operation sequences describes engine operations for each period of a print operation. Table 5-2. Power-on sequence describes each step of the power-on sequence. Table 5-1. Operation sequences Name Timing Purpose WAIT From power-on until the end of the main motor initial drive Detects presence of a print cartridge. Clears potential from the drum surface and cleans the transfer roller. See Table 5-2. Power-on sequence for a complete description of the WAIT (poweron) period. Also see General timing diagrams for detailed information about printer timing. STBY (standby) From the end of the WAIT or LSTR period until either a print command is sent from the formatter or the power is turned off. Prepares the printer to receive print commands INTR (initial From the time of the print command until Prepares the photosensitive drum for rotation) the pickup solenoid is turned on. printing. PRINT LSTR (last rotation) From the end of the INTR period until the top-of-page sensor detects the trailing edge of the media. Forms the image on the photosensitive drum and transfers the toner image to the media. From the end of the PRINT period until the main motor stops rotating. Delivers the last page of a print job. After LSTR, the printer either returns to STBY or, if another print command was sent from the formatter, enters INTR. Table 5-2. Power-on sequence Step Action 1 Power-on 2 CPU initialization 3 Video-interface communication start 4 Sensors check for residual media 5 Main motor initial drive 6 Fuser heater initial drive. The fuser heater reaches a surface temperature of 120°C. 7 Fuser-motor initial drive 8 Laser/scanner-motor initial drive 64 Chapter 5 Theory of operation ENWW