Sometimes the HP 33 S calculator may locks up or will not respond correctly. The calculator might require a reset for a variety of reasons. The first reset listed below will not affect the memory on the HP 33 S calculator. However, the other resets will erase the memory and restore the HP 33’s defaults. For this reason, it is important that you back up any critical data before resetting.

Resetting the calculator using the HP 33 S keyboard

To halt the calculator and reset the keyboard, follow the procedure below:

• Press and hold the {C} key on the HP 33.
• Press and hold the {LN} key (third key from the left on the top row).
• Release both keys at the same time.

The calculator may not appear to change, depending on what was displayed on the HP 33 screen.

To completely reset the calculator and erase all user memory, follow the procedure below:

• Press and hold {C}.
• Press and hold the first key from the top left and the first key from the top right.
• Release all three keys at the same time.
• The calculator will display ‘MEMORY CLEAR.’
• Press {C} to clear the message.

Resetting to drain the HP 33 S capacitor

If the above resets do not resolve the calculator problem, try one of the following resetting procedures:

HP 33 S Coin reset

• Remove the batteries.
• Lightly press a small coin (such as a dime) across both battery terminals.
• Hold the coin across both battery terminals for approximately ten seconds.
• Remove the coin, and replace with fresh batteries. (Insert the batteries with correct polarity. Note the picture beside the battery cover for polarity.)
• Press the {ON} key and the calculator should display ‘MEMORY CLEAR.’
• Press the {C} key to clear the message.

HP 33 S Paperclip reset

• Flip the HP 33 over and slide open the battery cover.
• Remove the batteries.
• Bend a paperclip enough to cross over from one terminal to the other.
• Hold the paperclip across the battery terminals for approximately ten seconds.
• Remove the paperclip, and replace with fresh batteries. (Insert the batteries with correct polarity. Note the picture beside the battery cover for details.)
• Press the {ON} key and the calculator should display ‘MEMORY CLEAR.’
• Press the {C} key to clear the message.