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To test the keyboard signals
Refer to chapter 6, "Replacing Assemblies," for instructions to remove covers and assemblies.
WARNING
Hazard voltages exist on the power supply, the CRT, and the CRT driver board. This
procedure is to be performed by service-trained personnel aware of the hazards involved,
such as fire and electrical shock.
1
Turn off the instrument and remove the power cable.
2 Without disconnecting the keyboard cable, follow the keyboard removal procedure
to loosen the keyboard. Leave the keyboard in place in front of the instrument.
3 Reconnect the power cable, install the operating system disk, then turn on the
instrument.
4 Run the Front Panel Test, pressing all of the keys.
5 If a random key is not operating, then go to the next step.
If a group of keys do not work, then check the keyboard voltages and signals.
Keyboard Connector Signals
Pin Signal Pin Signal
1 Keyboard Return 13 Keyboard Scan
2" 14"
3" 15"
4" 16"
5" 17"
6" 18"
7" 19LED
8" 20+5 V
9 Keyboard Scan 21 Ground
10 " 22 Knob
11 " 23 Ground
12 " 24 Knob
6 Allow the keyboard assembly to fall forward from the front panel. Separate the
elastomeric keypad and keyboard panel from the PC board.
7 Using a paper clip or screwdriver, short the PC board trace of the non-operating key
and look for an appropriate response on the display.
8 If the display responds as if the key were pressed, replace the elastomeric keypad.
If the display does not respond as if the key were pressed, replace the keyboard.
9 Check the RPG connector.
The RPG connector has a TTL pulse on pins 22 and 24 when the knob is being turned. Pin 20
of the connector is +5 V.
Troubleshooting
To test the keyboard signals
5–24