HP 54501A - Keyboard Signals Check

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 COLUMNDATA* 4 COLUMN DATA*
5 COLUMNDATA* 6 COLUMN
DATA*
7 COLUMNDATA* 8
COLUMN DATA*
9 COLUMNDATA* 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