Texas Instruments' graphing calculators are commonly used in American high schools and universities. They are handheld devices that run on AAA batteries, and feature LCD displays to render graphs and other mathematical aids. TI calculators are generally more stable than home PCs running complex operating systems, but problems can still occur, ranging from loss of memory to corruption of the operating system. Unless your calculator is broken beyond repair, a few simple troubleshooting steps will correct almost all problems you might run into during ordinary use.
Adjust the contrast of the LCD display as a first step if the calculator seems not to turn on properly, or anytime the screen is blank or totally black when the calculator is on. For model numbers lower than the TI-89, press the "2nd" key, then press and hold either the up arrow key (for blank screens) or the down arrow key (for black screens) until the contents of the display are again visible. For the TI-89 and TI-92, press the diamond key, then press and hold the plus or minus key to adjust the contrast.
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Replace the batteries if the calculator does not seem to turn on properly and adjusting the contrast does not fix the problem. If the calculator frequently loses its memory (a "RAM cleared" message may appear), replace the round lithium battery as well; this battery maintains power to the memory banks while the calculator is turned off, and the memory will be lost if it is drained. Adjust the contrast as in Step 1 after replacing the batteries.
Reset the calculator's memory in situations where the calculator's interface seems to work properly, but unexpected data or results appear. Many of the calculator's complex functions may be using data left over from previous uses, and clearing the RAM will clear out any residual values and let you start from scratch. For the TI-83 Plus and TI-84 Plus models, remove one of the AAA batteries, then hold the "Clear" key while turning the calculator on. On a TI-85, TI-86, or TI-89, reset the memory from the memory menu (press the "2nd" key then the "Mem" key to access it). For most models below the TI-89, remove a AAA battery and hold the "On" key for 20 seconds before replacing the battery. All of the data on the calculator will be lost, so if possible back up any programs or other data you need to keep by using a TI Connectivity cable before clearing the RAM. If any of these these methods do not work, remove all of the batteries, including the round lithium battery, for 5 minutes.
Reinstall the calculator's operating system from a PC using a TI Connectivity cable if you suspect its software may be corrupt. This is also the appropriate response if a message appears indicating the calculator is awaiting the installation of code, or if the calculator is stuck in a defragmentation process.
Inspect the calculator for physical damage; pay close attention to the data port. Foreign objects in the data port are the cause of a known issue which causes some models to respond sluggishly to key presses.