Tektronix Phaser 840, Service Manual

Page: 71 / 207

60 Phaser 840 and 850 Color Printers
Verifying power supply operation
The power supply is divided into two sections: the AC section used for heaters
and the DC section for control logic, printhead drivers and motors. Verifying the
power supply involves three steps:
■
Checking for proper AC voltage.
■ Inspecting the power supply fuses.
■
Testing for a shorted motor or solenoid driver, which shuts down the
power supply.
Measuring power supply voltages
Warning AC line voltages are present on the power supply and possibly in the
printer, via the heaters, while the printer is plugged into an AC outlet,
even if the power switch is off.
1. Turn off the printer and unplug it from its power outlet.
2.
AC Input: With a DMM set to measure AC voltages, measure the
power being supplied to the printer; it should measure between 87 to
128 VAC (115 VAC nominal) or 174 to 250 VAC (220 VAC nominal).
3. Proceed to the step, “Inspecting the power supply fuses” below.
If a heater shorts, F2 or F3 opens. The power supply does NOT shut
down, however, a
Service Required
error code is displayed on the
front panel.
Required tools
■
TORX T-20 screwdriver
■
Digital multi-meter (DMM)