Testing For A Shorted Motor; +24 Vdc Safety Interlocks - Tektronix Phaser 440 Service Manual

6
Troubleshooting
6-6 Phaser 440 Color Printer

Testing for a shorted motor

1.
Reinstall the power supply removed in the previous procedure.
2. Disconnect the drum motor, the thermal head lift motor, transfer roll
take-up motor and the paper-feed motor.
3.
Turn on the printer again to see if it does not overload now that the
motors are disconnected from the power supply.
If the power supply is functional, move to the procedure "Testing motor
resistances" on page 6-8.
If the motors and solenoids are working properly, but the power supply still
does not function, replace it. Refer to the Chapter 8 topic "Card cage and power
supply" on page 8-36.

+24 VDC safety interlocks

The printer features two +24 VDC safety interlocks. They are two switches, in
series, that can disconnect +24 VDC to all the motors. The +24 VDC supplied to
the motors is supplied through the interlock switches. The interlocks function
off of the top and front covers. Generally, when an interlock switch is opened,
the front panel COVER light is on.
1.
Turn off the printer.
2. Use a VOM, set to measure resistance, and test each switch when it is
opened and closed.
3. Inspect the wiring harnesses for pinched wires, nicks and opened
connections.
If you find a switch that does not function correctly, replace it.
If the switches work correctly and the DC voltages are correct, then the problem
may be an opened or otherwise bad motor. Proceed to the topic "Testing motor
resistances" on page 6-8.