Troubleshooting
4
90000 A-Series Service Guide
65
Checking the Backlight Inverter Voltages
The backlight inverter board MP13 is located in the front-left corner of the
oscilloscope.
• There is an input connector at one side of the board.
• Two output connectors are on the other end of the board to power the two
backlights, which are inserted into the flat panel display.
The output voltage is approximately 300-450 V
rms
, 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.
Backlight inverter board input voltage
Input pin #
7
6
5
4
3
2
1
Backlight OFF
0 V
0 V
0 V
0 V
0 V
0 V
0 V
Backlight ON
5 V
0 V
2.5 V
0 V
0 V
12 V
12 V
Summary of Contents for Infiniium 90000A Series
Page 1: ...Keysight Infiniium 90000 A Series Oscilloscopes Service Guide...
Page 6: ...6 90000 A Series Oscilloscopes Service Guide...
Page 12: ...12 90000 A Series Service Guide 1 General Information...
Page 18: ...18 90000 A Series Service Guide 2 Calibration...
Page 116: ...116 90000 A Series Service Guide 5 Replacing Assemblies...
Page 120: ...120 90000 A Series Service Guide 6 Replaceable Parts Fan and Acquisition Assembly...
Page 121: ...Replaceable Parts 6 90000 A Series Service Guide 121 Power Supply and PC Motherboard...
Page 122: ...122 90000 A Series Service Guide 6 Replaceable Parts Sleeve and Accessory Pouch...
Page 128: ...128 90000 A Series Service Guide 7 Theory of Operation Oscilloscope block diagram...
Page 135: ......
