The +5 Vdc Interlock Circuit - Xerox Phaser 7700 Service Manual

The +5 VDC Interlock Circuit

The 5 VDC Interlock Circuit runs from the 5 VDC LVPS to the L/H Door Switch,
then to the Engine Control Interface Board, out to the R/H Door Switch, back to
the Engine Control Interface Board, out to the Front Door, through the coil of the
LD Power Relay and back to the 5 VDC LVPS. This circuit helps identify which
door has interrupted the 24 VDC circuit.
If the circuit is complete, LD Power Relay activates, and 5 VDC is sent to the
Waste Cartridge Installed Interlock Switch and through all four Print Cartridge
connectors and to the Engine Control Interface Board. This signal merely
confirms that all Print Cartridges are installed. Individual missing components
are identified at power-up or when a door is closed (completing the 24 VDC
circuit) and the Engine Control Board interrogates the Print Cartridge NVRAM. If
the Print Cartridges are present, then the Waste Toner Cartridge is missing by
default.
1. With all doors closed and printer power on, check for +5VDC between P536-4
of the Engine Control Interface Board and frame ground. If not present, check
the LD Relay and the LH Cover Interlock Switch.
2. Check for +5VDC between P536-6 of the Engine Control Interface Board and
frame ground. If not present, check the Front Cover Interlock Switch.
3. Check for +5VDC between J568-7 (top pin) of the LD Power Relay and frame
ground. If not present, check the RH Cover Interlock Switch.
4.
Check for +5VDC between P536-1 of the Engine Control Interface Board and
frame ground. If not present, check the LD Power Relay, and the circuit
through the Waste Cartridge Sensor and the four Print Cartridge connectors.
5. If +5VDC is present, then replace the Engine Control Board (RRP 42, on page
7-190).
Service Quick Reference Guide - Troubleshooting
3-91