Technical data

Troubleshooting 4
4000 X-Series Oscilloscopes Service Guide 97
5 Check the keyboard supplies:
To check the fan
The fan speed is controlled by a circuit on the system board.
If the fan is running, perform the hardware self-tests. Go to
“To perform hardware self test” on page 76.
If the fan is not running, it may be defective. Follow these
steps:
1 Follow the instructions in “To prepare for internal
assembly troubleshooting” on page 83.
2 Disconnect the fan cable from the system board.
3 Connect the power cord, and turn on the oscilloscope.
4 Measure the fan voltage at the J4300 connector on the
system board.
See the following figure for the location of the fan
connector.
Test Point
(near J4303)
Expected Value Assemblies
Supplied
If Good If Bad
VP5V (+5V) +5 V ±3% Keyboard,
System Board
If good when the keyboard cable is
disconnected from the system
board, but bad when the keyboard
cable is connected, this indicates a
problem with either the keyboard
cable or the keyboard,
1 Turn off the oscilloscope, and
disconnect the power cord.
2 Replace the keyboard cable.
3 Connect the power cord, and
turn on the oscilloscope.
a If the problem is not fixed,
replace the keyboard.
Replace the system board.
VP13V_PRB
(+13V_PRB)
+13 V ±3% AutoProbe
Interface
Replace the system board.
VM15V_PRB
(-15V_PRB)
-13.2 V ±4% AutoProbe
Interface
VP7V5_PRB
(+7.5_PRB)
+6.28 V ±4% AutoProbe
Interface
VM7V5_PRB
(-7.5_PRB)
-6.25 V ±4% AutoProbe
Interface