Troubleshooting Checking High Voltage - 9
Checking High Voltage
This high-voltage check is a required procedure for some of the
symptoms in this chapter. After checking high voltage, return to
the symptom chart, if necessary.
Caution:
Do not attempt this procedure without the Apple high-
voltage probe (Apple part number 076-0392). Use only the
Apple high-voltage probe; other high-voltage probes will not
give accurate readings for this procedure.
±
Warning:
Read all of the warnings, notes, and steps of this
procedure before beginning.
±
Warning:
Voltage at the anode, with the power on, can cause
serious injury. Double-check all multimeter connections before
taking the reading.
±
Warning:
Probe the anode carefully. Serious damage and
injury may occur if the anode is knocked off while the CRT is
charged.
1 Turn off the monitor and computer. Disconnect the power
cords and video/USB cables. Wait at least two minutes for the
CRT to discharge.
2 Refer to the Take Apart chapter to remove the following:
• USB cover
• Rear housing
• Anode cap cover (but not the anode cap)
3 Attach the Apple high-voltage probe to a multimeter and
attach the ground wire to the chassis.
±
Warning:
Verify that the ground wire connection to the
chassis is secure.
4 With the power switches off, connect the power cords and
video/USB cables.
5 From the rear of the CRT—away from the CRT frame—
carefully insert the probe under the anode cap.
6 Turn on the computer and monitor.
7 The reading should be 27.3 kV DC (
±
0.3 kV DC). Most of the
voltage is across the high-voltage probe.
±
Warning:
Do not remove the probe from under the anode
cap until power is turned off. Injury or damage to equipment
may occur.
8 If reading is 0 VDC, contact Apple Technical Support.
9 Turn off the monitor.
10 Unplug the monitor.
11 Remove the probe from under the anode cap.
12 Go back to the symptom chart for the next cure, if necessary.
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