Troubleshooting The Low-Voltage Power Supplies; Troubleshooting The 3.3 Vdc And 5 Vdc Lvps - Xerox Phaser 7700 Service Manual

Troubleshooting the Low-voltage Power Supplies

3.3VDC, 5VDC and 24 VDCDC voltages are supplied by individual LVPS
boards. The 24 VDC LVPS requires the presence of a 5 VDC enabling signal to
operate.
Note Before troubleshooting power supply problems, disconnect the
Lower Tray Deck or Finisher, if installed, and restart the printer.
Verify the problem is still present or refer to the appropriate option
troubleshooting section.
1. Verify the printer is plugged in and the GFI is not tripped, Troubleshooting
AC Power on page 3-87
2. Remove the Image Processor Board cover and metal plate. Disconnect the
Relay Board Power Connector J300.
3. Switch the printer on. Check for 3.3VDC at J300-1, -2, -3 & -11. Check for
5VDC at J300-7. If 5 VDC is present check for 24 VDCDC at J300-9.
4. If no DC voltages are present, Troubleshooting AC Power on page 3-87
5. If 5 VDC is present but 3.3 VDC is not, Troubleshooting the 3.3 VDC and 5
VDC LVPS on page 3-88
6. If 3.3 VDC is present but 5 VDC and 24 VDC are not, Troubleshooting the 3.3
VDC and 5 VDC LVPS on page 3-88
7. If 5 VDC is present but 24 VDC is not, Troubleshooting the 24 VDC LVPS on
page 3-89

Troubleshooting the 3.3 VDC and 5 VDC LVPS

Note Switch off power and disconnect the power cord.
1. Remove the rear cover and rear shield.
2. Disconnect the harnesses to connectors P501, P574, P801 and 2ndBTR of the T1
HVPS, remove 3 screws and lower the T1 HVPS to horizontal (RRP 44, on page
7-192).
3. Connect AC Power and switch the printer on.
4. Check for proper AC Voltage at the connector at the bottom of the LVPS. If not
present go to the Troubleshooting AC Power section (link).
5. Check for 3.3 VDC or 5 VDC at the connector at the top of the LVPS. If correct
voltage is not present, unplug the connector and retest. If no voltage is present
replace the LVPS. If the voltage returns check the harness, Image Processor
Board, Engine Board and Relay Board for shorts.
3-88 Phaser 7700 Color Laser Printer