Hey guys! Ever find yourself in a situation where your trusty Casio FX-991EX PLUS calculator is acting up, displaying weird results, or just needs a fresh start? Don't worry; resetting it is a piece of cake! This guide will walk you through the process step-by-step, ensuring your calculator is back to its optimal state in no time. We'll cover everything from why you might need to reset it to the different methods you can use. So, grab your calculator, and let's get started!

Why Reset Your Casio FX-991EX PLUS?

Before we dive into the how, let's quickly touch on the why. There are several reasons why you might want to reset your Casio FX-991EX PLUS. Understanding these reasons can help you troubleshoot issues and decide if a reset is indeed the right solution.

• Incorrect Calculations: Sometimes, due to various settings or memory issues, your calculator might start giving you wrong answers. This can be super frustrating, especially during exams or important calculations. A reset clears the memory and default settings, often resolving these inaccuracies.
• Frozen Screen or Unresponsive Buttons: Has your calculator ever frozen on you? You press a button, but nothing happens. This can be due to a glitch in the system. A reset can often unfreeze the screen and get those buttons working again.
• Clearing Exam Mode Restrictions: In some regions or for specific exams, the calculator might be put into exam mode, which restricts certain functions. Resetting the calculator can remove these restrictions, allowing you to access all the features again. Just make sure you're allowed to use all functions before doing so!
• Selling or Giving Away Your Calculator: If you're planning to sell or give your calculator to someone else, you'll want to clear all your personal data and settings. A reset ensures that the new owner starts with a clean slate.
• Troubleshooting Unknown Issues: Sometimes, you might encounter issues you can't quite pinpoint. A reset can be a good first step in troubleshooting, as it eliminates any potential software glitches or incorrect settings.

Remember: Resetting your calculator will erase all stored data, including formulas, programs, and settings. So, be sure to back up anything important before proceeding. Now that we know why you might need to reset your calculator let's explore the different methods to do so.

Method 1: The Shift + 9 Reset

This is the most common and straightforward method to reset your Casio FX-991EX PLUS. It's quick, easy, and usually does the trick for most common issues. Here’s how to do it:

1. Press SHIFT: Locate the SHIFT button (usually in the top-left corner) and press it. This activates the secondary functions of the keys.
2. Press 9 (CLR): Look for the number 9 key, which also has the function CLR (Clear) written above it in a different color. Press 9. This will bring up the Clear menu on your screen.
3. Select Your Reset Option: You'll see three options:
   • 1: Setup: This option resets the calculator's setup settings, such as display, angle unit, and number format.
   • 2: Memory: This option clears the calculator's memory, including stored variables and formulas.
   • 3: All: This option performs a complete reset, clearing both setup settings and memory. This is the option you'll typically want to use for a full reset.
4. Choose 'All': Press 3 to select the 'All' option.
5. Confirm the Reset: The calculator will ask you to confirm your choice. Press the equals (=) key to execute the reset.
6. Wait for Completion: The calculator will take a few seconds to reset. Once it's done, the screen will display the initial setup menu or return to the calculation screen.

And that's it! Your Casio FX-991EX PLUS is now reset to its factory default settings. You can now reconfigure your settings and start using your calculator as if it were brand new.

Troubleshooting the Shift + 9 Reset

• Nothing Happens: If pressing SHIFT + 9 doesn't bring up the Clear menu, make sure the SHIFT key is properly activated. Sometimes, pressing it too quickly or lightly might not register. Try pressing it firmly and deliberately.
• Calculator Still Acting Up: If the reset doesn't solve your issue, there might be a more serious problem with the calculator. In this case, you might want to consider contacting Casio support or looking for professional repair services.

Method 2: Using the ON Button (The Hard Reset)

Sometimes, the standard reset method might not work, especially if the calculator is severely frozen or unresponsive. In such cases, a hard reset might be necessary. This method involves using the ON button in a specific way to force the calculator to reset.

Note: This method is less documented but has been known to work in certain situations. It might not work for everyone, but it's worth a try if the Shift + 9 method fails.

Here’s how to attempt a hard reset:

1. Press and Hold SHIFT and ON: Simultaneously press and hold the SHIFT and ON buttons. Keep holding them down.
2. Press 7: While still holding SHIFT and ON, press the 7 button.
3. Release All Buttons: Release all three buttons (SHIFT, ON, and 7) at the same time.
4. Check for Reset: The calculator should either reset immediately or display a diagnostic screen. If it displays a diagnostic screen, follow the on-screen instructions (if any).

If this method works, your calculator should now be reset. If it doesn't, don't worry; there might be other troubleshooting steps you can try, or it might indicate a hardware issue.

Why This Method Might Work

This method likely triggers a deeper level of reset within the calculator's firmware. The combination of buttons might access a hidden diagnostic mode or force the calculator to clear its memory and reload the default settings. However, it's important to note that this is not an officially documented method, so its effectiveness can vary.

Method 3: Battery Removal (The Last Resort)

If all else fails, you can try removing the battery from your Casio FX-991EX PLUS. This is a more drastic measure, but it can sometimes help in cases where the calculator is completely unresponsive. Removing the battery forces a complete power cycle, which can clear any residual memory or glitches.

Caution: Be careful when removing the battery, and make sure you have the correct replacement battery on hand.

Here’s how to remove the battery:

1. Locate the Battery Compartment: Turn your calculator over and locate the battery compartment. It's usually on the back of the calculator and secured with a small screw or latch.
2. Open the Battery Compartment: Use a small screwdriver to carefully open the battery compartment. Be gentle, as the plastic can be fragile.
3. Remove the Battery: Once the compartment is open, carefully remove the battery. Take note of the battery type and orientation.
4. Wait a Few Minutes: Leave the battery out of the calculator for at least 5 minutes. This allows any residual charge to dissipate.
5. Reinsert the Battery: Put the battery back into the compartment, making sure it's oriented correctly.
6. Close the Battery Compartment: Securely close the battery compartment with the screw or latch.
7. Turn On the Calculator: Press the ON button to turn on the calculator. It should now be reset to its factory default settings.

Potential Issues with Battery Removal

• Forgetting Battery Type: Make sure you remember the type of battery your calculator uses so you can replace it correctly.
• Damaging the Compartment: Be careful when opening and closing the battery compartment to avoid damaging the plastic or the screw.
• Data Loss: As with other reset methods, removing the battery will erase all stored data in the calculator's memory.

What to Do After Resetting Your Calculator

Once you've successfully reset your Casio FX-991EX PLUS, there are a few things you'll want to do to get it back up and running smoothly.

1. Reconfigure Settings: Go through the settings menu (usually accessed via SHIFT + MENU (SETUP)) and reconfigure your preferred settings, such as display, angle unit (degrees or radians), number format, and statistical settings.
2. Test Basic Functions: Perform some basic calculations to ensure that the calculator is working correctly. Try adding, subtracting, multiplying, and dividing simple numbers to verify accuracy.
3. Restore Important Data: If you backed up any important formulas or programs before resetting, now is the time to restore them. Refer to your calculator's manual for instructions on how to import data.
4. Familiarize Yourself with the Manual: Take some time to re-familiarize yourself with the calculator's manual. This can help you discover new features or remember how to use specific functions.
5. Keep Your Calculator Updated: Check the Casio website for any available firmware updates for your calculator. Updating the firmware can improve performance and fix bugs.

Conclusion

Resetting your Casio FX-991EX PLUS is a simple process that can solve a variety of issues. Whether you're dealing with incorrect calculations, a frozen screen, or simply want to start fresh, the methods outlined in this guide should help you get your calculator back in top shape. Remember to back up any important data before resetting, and be careful when removing the battery. With a little patience and these helpful tips, you'll be back to crunching numbers in no time! Happy calculating!