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1.3.4 High Voltage Discharge Procedure

This section describes how to discharge high voltages from the exposed

components of the display.

DANGER

+------------------------------------------------------------------------+

¦ ¦

¦  Hazardous voltages are present on the analog and video cards. ¦

¦ ¦

¦  The extra high tension (EHT) voltage on the CRT anode cap exceeds ¦

¦ 23 kV. Use extreme caution when working on the display with the ¦

¦ power on and the covers removed. ¦

¦ ¦

¦  Some adjustments require you to place tools close to the EHT ¦

¦ voltage. For safety and performance reasons, only plastic or ¦

¦ insulated metal tools should be used. ¦

¦ ¦

¦  Remove all jewelry before starting any repair process. ¦

¦ ¦

¦  Never leave the display unattended with the covers removed. This ¦

¦ applies whether or not the power cord is connected to the power ¦

¦ outlet. ¦

¦ ¦

¦  With the power cord connected, voltage may be present at the power ¦

¦ supply card even with power switched off. ¦

¦ ¦

¦  A static charge may be present at the line cord connector, at the ¦

¦ rear of the display, if the line cord is disconnected before the ¦

¦ power is switched off. ¦

¦ Always turn the power on/off switch off first, then wait ¦

¦ approximately five seconds before unplugging the power cord from ¦

¦ the back of the display. ¦

¦ ¦

¦  Under fault conditions, a static charge can remain on the CRT ¦

¦ anode long after the power cord has been disconnected. For this ¦

¦ reason, it is important to discharge the CRT anode before ¦

¦ disconnecting the anode lead. ¦

¦ ¦

+------------------------------------------------------------------------+

To avoid any shock hazard when working in the area of the high voltage

anode lead, use the following to discharge the CRT to ground:

 Screwdriver (part 1650855 or equivalent)

 Jumper (part 7838690 or equivalent) with an alligator clip (part

7838688 or equivalent) attached to each end; or Meter Lead Kit (part

6428104).

Please read the complete discharge procedure before starting; then

continue in the order given.

1. Power off the system and the display, and disconnect all cables (see

1.1.3).

2. Remove the tilt swivel stand (see "Tilt Swivel Stand" in topic 1.3.1),

or the lift tilt swivel stand (see "Lift Tilt Swivel Stand" in

topic 1.3.2).

3. Remove the rear cover (see 1.3.3).

4. Refer to Figure 3-5.

5. Connect one end of the jumper 1 to the CRT ground 2 , and the other

end to the screwdriver shaft 3 , except for models 8517 and 9517.

PICTURE 9

Figure 3-5. Connecting the Jumper for CRT Discharge

For display models 8517 and 9517, connect the jumper between the shield

around the integrated tube component and the uninsulated part of the

screwdriver shaft as shown in Figure 3-6. This will discharge the anode

of the CRT 1 to the ITC shield (ground).

PICTURE 10

Figure 3-6. CRT Discharge Connection for 8517/9517 Displays

PS/2 Displays Maintenance Manual

High Voltage Discharge Procedure

1.3.4 - 1