HP 48g Graphing Calculator - Manual (Page 447)

1. Press and hold (ON )■
2. Press and release the “C” key (the key with C next to it).
3. Release (M)- The empty stack display should appear.
If the self-test indicates an internal ROM or RAM failure (if I ROM OK
and I RAM OK are not displayed), the calculator requires service.
The diagnostic self-test should be successfully completed before
running any of the tests described in the following sections.
To halt the self-test (system halt):
Keyboard Test
This test checks all of the calculator’s keys for proper operation.
To run the interactive keyboard test:
1. Turn on the calculator.
2. Press and hold (ON ).
3. Press and release the “D” key (the key with D next to it).
4. Release
5. Press and release the “E” key (the key with E next to it). KB.D1
will appear in the upper left corner of the display.
6. Starting at the upper left corner and moving left to right, press
each of the 49 keys on the keyboard.
If you press the keys in the proper order and they’re functioning
properly, the calculator emits a high-pitch beep at each press of a
key. When you press the 49th key, ((Q, the displayed message should
change to KBDl OK.
If you press a key out of sequence, a five-digit hexadecimal number
will appear next to KBDl. Rerun the test by repeating steps 2 through
6 above.
If a key isn’t functioning properly, the next keystroke displays the hex
location of the expected and the received location. If you pressed the
keys in order and got this message, the calculator requires service.
Be sure to include a copy of the error message when 3 fou ship the
calculator for service.
Support, Batteries, and Service A-11