160 Chapter 7
Troubleshooting the Processor, Power Supply, and Display
Isolating a Display Problem
Isolating a Display Problem
NOTE There are no front panel adjustments for intensity and contrast of the
LCD.
1. Verify the instrument went through a complete power-on sequence.
Refer to "Troubleshooting Power-up Problems" on page 46.
2. If the display is dark, (not visible), connect an external VGA monitor
to the rear panel VGA output connector on the instrument. Some
multisync monitors might not be able to lock to a 60 Hz sync pulse. If
the video information is not present on the external VGA monitor,
the most probable cause is the A26 CPU assembly.
3. If the external VGA monitor is functioning, verify that the front
panel ribbon cable (W2) is properly plugged into the motherboard.
4. If W2 is properly connected, suspect cable W5 from the LCD display,
a defective A2 Front Panel Interface board, one or both of the
inverter boards (A2A1 and A2A2) mounted on the interface board, or
the LCD assembly itself (A1).
Verifying the Inverter Boards
WARNING High voltage is present on the inverter boards and the front
panel interface board. Be careful when measuring the following
signals and voltages.
NOTE In order to access the front panel boards for measurements, it is
necessary to drop the front frame from the deck and remove the front
frame shield. Refer to Chapter 11 for these procedures.
Measure the signals and voltages as indicated in Figure 7-2. If the
signals and voltages measure good, the inverter boards are functioning
correctly.
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