Tektronix Phaser 840, Service Manual

Page: 74 / 207

Service Guide 63
Testing for a shorted motor
1. Reinstall the power supply if removed in the previous procedure.
2. Disconnect the process motor, the Y-axis motor, X-axis motor and the
cap/wipe/purge assembly motor wiring harness.
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 following procedure, “Testing
motor and solenoid resistances”.
If the motors and solenoids are not shorted, but the power supply still does not
function, replace the power control board.
Testing motor and solenoid resistances
1. Turn off the printer and disconnect the power cord.
2. With a DMM set for measuring resistance, test each motor's windings
for correct resistance (disconnected from the printer). Rotate the
motor's drive shaft slightly while taking the measurement.
Testing the cap/wipe/purge vacuum system
Refer to the topic “Evaluating the printhead and cap/wipe/purge system” on
page 80.
Table 5 Motor and solenoid resistances
Motor or solenoid Phaser 840 printer
Resistance (approximately) Phaser 850 printer
Resistance (approximately)
Process motor 2.9 ohms +/-15% (Difficult to
measure due to variability at the
brush/commutator interface.) 4.3 ohms +/-15% (Difficult to
measure due to variability at the
brush/commutator interface.)
Y-axis motor 1.4ohms +/- 15% (Difficult to
measure due to variability at the
brush/commutator interface.) 1.4ohms +/- 15% (Difficult to
measure due to variability at the
brush/commutator interface.)
X-axis motor 12.5 ohms/phase (red-to-yellow
and blue-to-orange 12.5 ohms/phase (red-to-yellow
and blue-to-orange
Paper-feed motor 1.5 +/- 20% ohms/phase 1.5 +/- 20% ohms/phase
Maintenance drawer
camshaft electric
clutch 186 ohms +/- 15% 132 ohms +/- 15%
Paper-pick electric
clutch 186 ohms +/- 15% 186 ohms +/- 15%
Cap/wipe/purge and
feed clutch 125 ohms +/- 12% 124 ohms +/- 5%
Transfix cam solenoid 108 ohms +/- 10% 108 ohms +/- 10%