HP 8000dn Service Manual - Page 130

Engine Test Microswitch The Engine Test Microswitch, located on the DC Controller PCA, is activated manually through the square access hole at the right rear of the printer (see Chapter 6). This switch causes the print engine to perform an internal self test diagnostic which bypasses the Formatter PCA and then prints a full page of black parallel lines. This test is useful for troubleshooting printer problems because it isolates the print engine from the Formatter PCA. The engine test printout prints from Tray 3 and can be activated with the Formatter PCA removed. For more information, see Engine Test in Chapter 7. Motors See the General Timing Diagram (figure 5-23 on page 140) for specific timing details for the printer motors. The Main Motor, MT1, is controlled by the DC Controller PCA. The Main Motor drives the Main Gear Assembly and rotates during the Initial Rotation period (following power-on), the Print period, the Last Rotation Period, or whenever the printer front door is opened and closed. The Scanner Motor is controlled and monitored by the DC Controller. It rotates the laser/scanner mirror during the Initial Rotation period and the Print period. The Fan Motors are controlled and monitored by the DC Controller PCA. All four fans operate at full speed during the printing modes. All four fans turn off in the PowerSave mode after the Fuser cools down. The drive signal for the Tray 2 and 3 Paper Pickup Motor, SMT1, is provided by the DC Controller PCA through the Paper Input Unit (PIU) PCA mounted on the right side of the PIU. When the job instructions call for paper to be supplied by Tray 2, SMT1 rotates in a forward direction and drives the Pickup roller for Tray 2. When paper is supplied by Tray 3, SMT1 rotates in the reverse direction and drives the Pickup roller for Tray 3. 106 Chapter 5 Functional Overview EN