Keyboard Signals Check - HP 54501A Service Manual

6-16 . HP 54501 A Keyboard Signals Check
1 .
To isolate faulty elastomeric keypad or keyboard when random key(s) not operating, perform
the following steps :
a .
Remove top cover and and power supply. (Refer to Removal and Replacement of Power
Supply Assembly, if necessary .)
b .
Remove the four screws securing the keyboard assembly to the front panel .
c . Replace power supply and apply power to the instrument.
d .
Run Keyboard Self Test . If keydown power-up was not performed when power was ap-
plied, do so before invoking the self test.
e.
Allow keyboard assembly to fall forward from front panel and separate the elastomeric
keypad from the printed circuit keyboard .
f .
Short keyboard trace (with a paper clip or screwdriver) of non-operating key and look for
appropriate response on display .
9.
If display responds as if key were pressed, replace elastomeric keypad .
h.
If display does not respond to short as if key were pressed, replace keyboard .
2.
The row scan signal of 60 Hz is present at all times . This signal is found on pins 14 through
20 of keyboard cable connector . The same signal is on pins 3 and 9 through 13 only when a
key is being pressed . Refer to table 6-4 for all signals going to and from the keyboard .
Table 6-4 . Keyboard Connector Voltages and Signals
* Row scan signal of 60 Hz is on these pins only when a key in the
corresponding column is pressed .
HP 54501A SERVICE
6-21
PIN SIGNAL PIN SIGNAL
1 RPG A 2 RPG B
3 COLUMN DATA* 4 COLUMN DATA*
5 COLUMN DATA* 6
COLUMN DATA*
7 COLUMN DATA* 8
COLUMN DATA*
9 COLUMN DATA* 10 COLUMN DATA*
11 60 HZ SCAN 12 COLUMN DATA*
13 60 HZ SCAN 14
60 Hz SCAN
15 60 HZ SCAN 16 60 HZ SCAN
17 60 HZ SCAN 18 60 HZ SCAN
19
+5 (DIGITAL) 20 60 HZ SCAN