2-4 Phaser 4400 Laser Printer Service ManualGeneral Notes on Troubleshooting1. Unless indicated otherwise, the instruction ìswitch ON printer main powerî meansfor you to switch ON printer power and let the printer proceed through POST.2. When instructed to take voltage, continuity or resistance readings on wiringharness, proceed as follows: check P/J 232ñ1 to P/J 210ñ5 by placing the red probe(+) of your meter on pin 1 of P/J 232, and place the black probe (ñ) of your meteron pin 5 of P/J 210.3. When you are instructed to take voltage readings between ìP/J 232 P/J 210î(without specified pin numbers), check all pins. Refer to the section Wiring Dataon 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 (ñ) is generallyconnected to a pin that is either RTN (Return) or SG (Signal Ground). You cansubstitute any RTN pin or test point in the printer, and you can use FG (frameground) in place of any SG pin or test point.5. Unless a troubleshooting procedure instructs otherwise; before measuring voltagesmake sure the printer is switched ON, the Imaging Unit and the paper trays are inplace, 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 componentis receiving the correct voltage value from the power supply and if gating (avoltage drop) occurs during component actuation. Gating signals may be nothingmore than a pulse, resulting in a momentary drop in voltage that may be difficult orimpossible to read on the average multi-meter.7. When a Troubleshooting Procedure instructs you to replace a non-sparedcomponent and that component is part of a parent assembly, you should replace theentire parent assembly.Voltage MeasurementsPower and signal grounds are connected to frame ground. You can perform all circuittroubleshooting using the metal frame (chassis) as the grounding point. If you needmore 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 thissection.Voltage MeasurementsStated Measured Stated Measured+3.3 VDC +3.0 to 3.6 VDC +24.0 VDC +21.6 to +26.4 VDC+5.0 VDC +4.8 to +5.2 VDC 0.0 VDC Less than +0.5 VDC
