To Test The Keyboard Signals - Agilent Technologies 1670G Series Service Manual

Troubleshooting

To test the keyboard signals

Using an oscilloscope, probe pins 1 and 2 of J4 for +3.3Vdc
4
If +3.3Vdc is present on J4 of pins 1 and 2, and digital signals are present on the video data
pins indicated above, then the CPU board video circuit is operating properly.
Remove power. Allow time for the capacitors in the power supply to discharge
5
before disconnecting the power supply, doing the repair, and reassembling the
instrument.
To test the keyboard signals
Refer to chapter 6, "Replacing Assemblies," for instructions to remove covers and assemblies.
Hazardous voltages exist on the power supply and the LCD display. Only service-trained
W A R N I N G
personnel who are aware of the hazards involved, such as fire and electrical shock, should
perform this procedure.
Turn off the instrument and remove the power cable.
1
Without disconnecting the keyboard cable, follow the keyboard removal procedure
2
to loosen the keyboard. Leave the keyboard in place in front of the instrument.
Reconnect the power cable, then turn on the instrument.
3
Run the PV Front Panel Test, pressing all of the keys.
4
If a random key is not operating, go to the next step.
5
If a group of keys do not work, then check the keyboard voltages and signals.
Keyboard Connector Signals
Pin
1
2
3
4
5
6
7
8
9
10
11
12
5–22
Signal Pin
Keyboard Return 13
" 14
" 15
" 16
" 17
" 18
" 19
" 20
Keyboard Scan 21
" 22
" 23
" 24
Signal
Keyboard Scan
"
"
"
"
"
LED
+5 V
Ground
Knob
Ground
Knob