Tektronix Phaser 840, Service Manual

Page: 72 / 207

Service Guide 61
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 right side of the power supply and remove
power supply.
3.
With a DMM, determine that the fuses on the power
supply are functional. Measure the resistance of all fuses to LINE as
indicated on the power supply’s shield.
If any fuse opens, the power supply does not function and should be
replaced.
Caution Fuses 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, 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 62.
Fuse F1 is for the DC power supply, all DC outputs.
Fuse F2 is for the following heaters:
■ H3 Jet Stack Left
■ H4 Paper PreHeat
■ H10 Jet Stack Right
■
H11 Reservoir #2
■
H12 Drum #2
■
H14 Reservoir #4
Fuse F3 is for the following heaters:
■ H1 Drum #1
■ H2 Reservoir #1
■ H5 Black Ink Melt
■
H6 Magenta Ink Melt
■
H7 Cyan Ink Melt
■
H8 Yellow Ink Melt
■
H9 Cap Wipe Heat
■
H13 Reservoir #3