The +5 Vdc Interlock Circuit - Xerox 7700DX - Phaser Color Laser Printer 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 +5 VDC 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 +5 VDC between P536-6 of the Engine Control Interface Board
and frame ground. If not present, check the Front Cover Interlock Switch.
3. Check for +5 VDC 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 +5 VDC 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 +5 VDC is present, then replace the Engine Control Board (RRP 42, on
page 7-206).
3-92 Phaser 7700 Color Laser Printer Service Manual