Xerox 4400DT Service Manual - Page 41

General Notes on Troubleshooting 1. Unless indicated otherwise, the instruction "switch ON printer main power" means for you to switch ON printer power and let the printer proceed through POST. 2. When instructed to take voltage, continuity or resistance readings on wiring harness, proceed as follows: check P/J 232-1 to P/J 210-5 by placing the red probe (+) of your meter on pin 1 of P/J 232, and place the black probe (-) of your meter on pin 5 of P/J 210. 3. When you are instructed to take voltage readings between "P/J 232 P/J 210" (without specified pin numbers), check all pins. Refer to the section Wiring Data on page 9-1 for the location of all wiring harnesses and pins. 4. When you are instructed to take a voltage reading, the black probe (-) is generally connected to a pin that is either RTN (Return) or SG (Signal Ground). You can substitute any RTN pin or test point in the printer, and you can use FG (frame ground) in place of any SG pin or test point. 5. Unless a troubleshooting procedure instructs otherwise; before measuring voltages make sure the printer is switched ON, the Imaging Unit and the paper trays are in place, and the interlock switches are actuated. 6. All voltage values given in the troubleshooting procedures are approximate values. The main purpose of voltage readings is to determine whether or not a component is receiving the correct voltage value from the power supply and if gating (a voltage drop) occurs during component actuation. Gating signals may be nothing more than a pulse, resulting in a momentary drop in voltage that may be difficult or impossible to read on the average multi-meter. 7. When a Troubleshooting Procedure instructs you to replace a non-spared component and that component is part of a parent assembly, you should replace the entire parent assembly. Voltage Measurements Power and signal grounds are connected to frame ground. You can perform all circuit troubleshooting using the metal frame (chassis) as the grounding point. If you need more information to locate connectors or test points, refer to Wiring Data on page 9-1. Unless otherwise specified, the following voltage tolerances are used within this section. Voltage Measurements Stated +3.3 VDC +5.0 VDC Measured +3.0 to 3.6 VDC +4.8 to +5.2 VDC Stated Measured +24.0 VDC +21.6 to +26.4 VDC 0.0 VDC Less than +0.5 VDC 2-4 Phaser 4400 Laser Printer Service Manual