Inspecting The Power Supply Fuses; Safety Interlocks - Tektronix Z740/N - Phaser 740 Color Laser Printer Service Manual

Inspecting the power supply fuses

The 115 VAC power supply features a 8 A and a 10 A fuse. The 220 VAC power supply
fuse uses a 4 A and a 5 amp fuse.
1.
Turn off the printer.
2. Remove the power supply.
3.
Remove the power supply cover to access the fuses.
4.
Visually, and with a VOM, check to determine that the fuse is in working
order.
If the fuse is good, but the printer's power supply does not output DC voltages,
proceed to the next topic, "Testing for a shorted motor."

Safety interlocks

The printer features four safety interlock switches:
Front door-opened switch.
Right side door-opened switch.
Left door-opened switch.
Optional Lower Tray Assembly door switch.
When any of the switches are opened, the +24 VDC supply to the motors is shut
down, as well as the high-voltage power supply.
1.
Test the functionality of the interlock using the service tests described in
"Service tests" on page 57.
2. Turn off the printer.
3.
With a VOM, set to measure resistance, test each switch when it is opened
and closed.
4.
Inspect each switch's wiring harness for pinches, nicks or open connections.
If you find a switch that is defective, replace it.
If the switches work correctly and the DC voltages are correct, then the problem may
be an open or otherwise faulty motor.
Service Guide
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