Agilent Technologies 54502A Manuale di Servizio Scaricare il pdf (Pagina 103)

Keyboard Signals

Check

Isolate a faulty elastomeric keypad or keyboard when random key(s) not operating

by performing the following steps.

1. Remove instrument power cable.

2. Without disconnecting the keyboard cable, follow keyboard removal

procedure to loosen keyboard. Leave keyboard in place in front of

instrument.

3. Apply power.

4. Run Keyboard Self Test and press all keys.

5. Allow keyboard assembly to fall forward from front panel. Separate the

elastomeric keypad and keyboard panel from the PC board.

6. Short PC board trace (with a paper clip or screwdriver) of non-operating key

and look for appropriate response on display.

7. If display responds as if key were pressed, replace elastomeric keypad.

8. If display does not respond as if key were pressed, replace keyboard.

The RPG connector has a TTL pulse on pins 1 and 3, when the knob is being

turned. Pin 5 of the connector is + 5 V.

The ROW (scan) signal is approximately 60 Hz, a low duty-cycle pulse. It is

continually present on pins 11 through 18 of the keyboard cable. Because of the

resistance of the keypad contacts, the signal does not appear the same on the

COLUMN (data) pins when keys are pressed. Refer to the following table for

signals going to and from the keyboard.

PIN SIGNAL PIN SIGNAL

1 RPGA 2 RPGB

3 COLUMN 1 (Data) 4 COLUMN 2 (Data)

5 COLUMN 3 (Data) 6 COLUMN 4 (Data)

7 COLUMN 5 (Data) 8 COLUMN 6 (Data)

9 COLUMN 7 (Data) 10 COLUMN 8 (Data)

11 ROW 8 (Scan) 12 ROW 7 (Scan)

13 ROW 6 (Scan) 14 ROW 5 (Scan)

15 ROW 4 (Scan) 16 ROW 3 (Scan)

17 ROW 2 (Scan) 18 ROW 1 (Scan)

19 +5 V (Digital) 20 GROUND (Digital)

Table 6-3. Keyboard Connector Voltages and Signals

Service HP 1650B/1651B

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Agilent Technologies 54502A Manuale di Servizio Pagina 103