Oh no! That sounds bad. Here, I don't have a Texas instrument calculator, but I can give you some tips! :)
1: Please check the volts on both the battery and the display, if they look fine, go to step 2.
2: Look for any damaged or misplaced cables. Sometimes they can cause a problem, oh and look for loose screws too.
3: If it still dosn't work, it might be a circuit board problem. There's not much you could do with that. We could buy another one on ebay, here's one I found. [link|https://www.ebay.com/itm/186730756717?_skw=Ti-82&itmmeta=01JAY0FH3PV8RWET13XCK95QV5&hash=item2b7a053a6d:g:j00AAOSw6p9nDcDn&itmprp=enc%3AAQAJAAAA4HoV3kP08IDx%2BKZ9MfhVJKmExDvHL0%2BsxEkCs4IuZN8ynBIgKVQSTvI3heOwOFyOChok7othl6wVb7q1s61x7zlnXE432UJ7UEREBbHNdV3F9siH6%2F7Gc75WrV%2FsJsiq7RYBmiWdv7CvIppiXp7FKrkzCIaMNyoPyz4IR4V2D%2FAxwL4j7kMQStbnI%2Fye0MP1DBNx68pB%2B7P3WeNFsmG5a8TVOudzL1XTFCqmr0yt5vNOAnWTeCpdlFJSmqZ7vHPyZvk%2B1E%2BU09LARPPuiMvRnWLi7Ya%2B3G%2BY455Xeknd52iY%7Ctkp%3ABFBM9pG-wNdk|TEXAS INSTRUMENTS TI-82 PERFECTLY WORKING SCIENTIFIC CALCULATOR|new_window=true]
Thank you for your patience! :D