HP 48g Graphing Calculator - Manual (Page 445)

5. Install a fresh, 3-volt 2016 coin cell in the plastic battery holder,
and reinsert the holder (with battery) into the card. Be sure to
install the battery with the side marked “+” toward the front of the
card.
6. Mark the card with the battery-installation date, and set an alarm
for 1 year from that date to remind you to change it. (If you
unplug the card, the HP 48 can’t check the card’s battery level.)
7. Replace the plug-in port cover.
Testing Calculator Operation
Use the following guidelines to determine whether the calculator is
functioning properly. Test the calculator after every step to see if
operation has been restored. If your calculator requires service, see “If
the Calculator Requires Service” on page A-16.
If the calculator won’t turn on or doesn’t respond when you press
the keys:
1. Make sure that three fresh batteries are correctly installed in the
calculator.
2. Press and release (H)-
3. If the calculator comes on, but the display is blank, press and hold
fON 1, press and release (+() several times until characters become
visible, then release
(ON
). If no characters appear in the display, the
calculator requires service.
4.
If
a halted program won’t respond when you press (CANCEL), try
pressing ( cancel ) again.
5. If the keyboard is “locked,” perform a system halt;
a. Press and hold
(ON ).
b. Press and release the “C” key (the key with C next to it).
c. Release
(ON
). The empty stack display should appear.
d. If the problem still exists, perform a manual system halt (see
page 5-17).
Support, Batteries, and Service A-9