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To check the backlight inverter voltages
The backlight inverter board is accessed by opening the front chassis as described
in the "Replacing Assemblies" chapter. Below is a picture showing what the
inverter board looks like (this picture is of the back of the front chassis - the display
is on the other side of this piece).
This is the backlight inverter board
• There is an input connector at one side of the board.
• There are two output connectors on the other end of the board, that power the
The output voltage is approximately 300-450 Vrms, 40 kHz (measured
differentially between the two wires) when the backlight is illuminated. The
voltage is approximately 1 kV before the backlight tube is illuminated. A red LED
on the backlight inverter board illuminates when the output voltage is present.
When the backlight goes off (when the oscilloscope's operating system switches
to screen saver mode) the voltage on pins 1 and 2 (with respect to ground) slowly
decays to 0 V.
The outputs are controlled by the input. Notice that input pin 5 goes low to enable
the output voltage. These pins can be reached at J1 on the display board MP12.
Table 11 Backlight Inverter Board Input Voltages
Input Pin #
Backlight OFF
Backlight ON
Infiniium 9000 Series Oscilloscopes Service Guide
two backlights which are inserted into the flat panel display.
7
0 V
5 V
6
5
4
0 V
0 V
0 V
0 V
2.5 V
0 V
Troubleshooting
3
2
1
0 V
0 V
0 V
0 V
12 V
12 V
4
75
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Troubleshooting
