Zenith Z-171 Series Service Manual page 80

Page
6-6
System Checkout and Troubleshooting
STEP
PROCEDURE
YES
NO
Id Disconnect the AC adapter from the com-
puter. Use a DVM or a YOM to check
the output voltage of the AC adapter. Does
the output voltage equal approximately 15
VDC? Ih Ie
WARNING: The AC adapter contains circuitry capable of generating
dangerous high voltages. Use extreme care when opening this unit Refer
to "Final Connections", Chapter 2 for instructions on how to open the
unit
Ie Unplug the unit and remove the cover.
Is the fuse blown?
If Replace the fuse and return to step 1.
19
Is the voltage selector jumper properly
set?
Ih Select the proper setting and return to
step 1.
Ii Replace the AC adapter and return to step
1.
Ij Check the ELON signal from the main
logic board. Use a DVM or YOM to mea-
sure the voltage at pin 15 of connector
J5. Is the voltage greater than 3 VDC?
lk Replace the main logic board and return
to step 1.
11 Check the power output from the DC
power board to the LCD by using an oscil-
loscope. Measure the waveform at the two
leads of capacitor CI as illustrated in Fig-
ure 6-2. Does the waveform approximate
If
Ig
Ii
Ih
Ii
lk