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HP 20S Calculator - Resetting the Calculator

Description

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

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Resetting the calculator using the keyboard

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

  1. Press and hold the [C] key.

  2. Press and hold the third key from the left on the top row.

  3. Release both keys at the same time.

  4. The calculator will now display "0.00" (if the number of decimal places is set to two.)

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

  1. Press and hold the [C] key.

  2. Press and hold the first key from the left (the N key) and the first key from the right (the sigma +) on the top row. Release all three keys at the same time.

  3. You should see "ALL CLr" on the display.

  4. Pressing the [C] key will clear the message.

  5. The calculator will display "0.00."

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Resetting to drain the capacitor

If the above resets do not resolve the calculator issue, try one of the following resetting procedures.

Coin reset

  1. Take the batteries out.

  2. Lightly press a coin across both battery terminals.

  3. Hold the coin across the battery terminals for approximately ten seconds.

  4. Replace with a fresh set of batteries, being sure to follow the polarity assigned. Note the picture beside the battery cover.

  5. The calculator should display "ALL CLr."

  6. Press the [C] key to clear the message.

Paperclip reset

  1. Take the batteries out.

  2. Bend a paperclip out enough to cross over from one terminal to the other.

  3. Hold the paper clip across the battery terminals for approximately ten seconds.

  4. Replace with a fresh set of batteries, being sure to follow the polarity assigned. Note the picture beside the battery cover.

  5. The calculator should display "ALL CLr."

  6. Press the [C] key to clear the message.

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Other solutions

If the calculator did not display the "ALL CLr" message after resetting, or if it did not correct the error, then remove the batteries for 24 to 48 hours.

NOTE: The batteries must be removed for at least 24 hours to drain the capacitor completely.

After letting the calculator sit without batteries for at least 24 hours, replace with fresh batteries.

If the calculator continues to malfunction, it will need to be sent in for repair or replaced.

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