Phaser 4400 Laser Printer Service Manual 3-13Inoperative Front PanelFront Panel is not operative (no backlight or LED).Erratic Printer OperationInoperative Front Panel Troubleshooting ProcedureStep Actions and Questions Yes No1 1. Disconnect J790 on the Image Processor Board.2. At J790 on the Image Processor Board, measure thevoltage between frame ground and each pin of J790listed here.Are all the voltages are correct?Go to step 2. Replace theImageProcessorBoard(RRP 9.2 onpage 6-88).2 1. Disconnect J550 from the Front Panel.2. Measure continuity on all wires between J550 andJ790.Are all checks good?Replace theFront PanelAssembly(PL 1.1,page 7-2).Replace theFront PanelHarness(PL 1.1,page 7-2).Erratic Printer Operation Troubleshooting ProcedureStep Actions and Questions Yes No1 1. Disconnect all host cables.2. Enter Service Diagnostics and select Test Print. Run15 to 20 test prints.Does the printer generate test prints?Go to step 4. Go to step 2.2 1. Switch the printer power OFF.2. Disconnect P/J PN1 from the LVPS Assembly.3. Switch the printer power ON.4. Check the voltage between P/J281 pin 7 and frameground.Is the voltage +5.0 VDC?Go to step 3. Switch theprinter powerOFF andreconnectPN1. Go toPowerSupply onpage 3-14.3 Replace the Engine Logic Board (RRP 9.3 onpage 6-89).Does the problem still appear?Go toElectricalNoise onpage 3-33.Problemsolved.4 Does the printer RESET while generating testprint?Go to PowerSupply onpage 3-14.Go to step 5.Pin Voltage Pin Voltage1 0.0 VDC 6 3.4 VDC2 3.4 VDC 7 0.0 VDC3 0.0 VDC 8 0.0 VDC4 3.4 VDC 9 5.0 VDC5 0.0 VDC 10 5.0 VDC
