Technical data

96 4000 X-Series Oscilloscopes Service Guide
4 Troubleshooting
To check the keyboard supplies
This procedure checks the keyboard supply voltages on the
system board test points when the keyboard cable is
disconnected.
If one or both of these voltages are bad when the keyboard
cable is connected but good when the cable is disconnected,
it indicates problems with the keyboard assembly.
1 Follow the instructions in “To prepare for internal
assembly troubleshooting” on page 83.
2 Connect the negative lead of the multimeter to a ground
point on the oscilloscope.
3 With the power cord disconnected:
a Disconnect the keyboard cable from the system board
connector J3403.
4 Connect the power cord, and turn on the oscilloscope.
Test Point
(near J2000)
Expected Value Assemblies
Supplied
If Good If Bad
VP3V3
(+3.3V)
+3.3 V ±3% LCD, System
Board
If good when the display cable is
disconnected from the system
board, but bad when the display
cable is connected, this indicates a
problem with either the display
cable or the display assembly,
1 Turn off the oscilloscope, and
disconnect the power cord.
2 Replace the display cable.
3 Connect the power cord, and
turn on the oscilloscope.
If the problem is not fixed, replace
the display assembly.
Replace the system board.