Tektronix Phaser 340 Service Manual page 132

6
Troubleshooting
6-6 Phaser 340 Color Printer
4. Plug in the printer and turn it on.
5. Using the Tektronix DMM 252/254 set for Hz (also, press the blue
button), measure the AC sense test point. If the power supply can
sense the AC input voltage, you should measure ~8.2 kHz for
115 VAC, or ~16.4 kHz for 220 VAC. The range varies from 6 kHz for
87 VAC to 17 kHz for 250 VAC.
6. AC Output: Fuses F1 through F5 are AC fuses. Fuse F1 is the AC
input fuse for the DC section of the power supply. If this fuse is open,
the power supply does not function.
Caution
Fuses F2, F3, F4 and F5 are used for the AC heaters within the
printer; they protect the power supply from, most often, a shorted
triac. If a F2 through F5 fuse 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.
7.
Proceed to the step, "Inspecting the power supply fuses" on page 6-8.
If a heater shorts, the respective fuse (F2 -F5) opens. The power
supply does NOT shut down, however, a Service Required error
code is displayed on the front panel.
Using the Tektronix DMM 252/254 set for Hz (also, press the blue
button), measure the heater triac control lines test points at the bottom
of the power supply. When a heater is turned on full, you should
measure a 30 Hz digital signal activating that particular heater's triac.
If not, then the main board has failed. Note that when the heater is not
activated, the reading will be zero. Also, if the heater is being partially
activated, the reading will be some fluctuating intermediate value less
than 30 Hz.
8.
DC Output: Refer to Appendix C, "Wiring Diagrams" for more
details on other voltage test points. The test points are printed on the
power supply's plastic safety cover.
If you do not measure the expected DC voltages, proceed to the next step,
"Inspecting the power supply fuses."