Tektronix Phaser 840, Quick Reference Manual

Page: 50 / 160

40
Phaser 840 Color Printer
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 the 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.
Inspecting the power supply fuses
Three fuses (F1 - F3) are mounted on the power supply.
1. Turn off the printer and remove the power cord.
2. Remove the screws securing the power supply. Disconnect the wiring
harnesses plugged into the power supply and remove power supply.
3. With a DMM, determine that the fuses on the power
supply are functional. Fuse F1 is the AC input fuses for the DC section
of the power supply. If F1 opens, the power supply does not function
and should be replaced.
Caution
Fuse F2 and F3 are used for the AC heaters within the printer;
they protect the power supply from, most often, a shorted triac. If
F2 or F3 blows, it is best to replace the power supply rather than
the fuse. Otherwise, with the fuse replaced, but the triac shorted,
AC power may be applied to the heater without the printer even
being turned on, resulting in a thermal runaway condition.
If the fuses are functional, but the printer's power supply does not output DC
voltages, proceed to the topic, “Testing for shorted drivers” on page 41.