I have a TI-Nspire CAS calculator, probably by now two years old. Recently when i turn it on the brightness of the screen has been going from normal, to so dark i cannot see the display. I have tried using the (CTRL) and - key to adjust brightness, which works up until a point, but its is still extremely hard to see.

SOURCE: TI-82 Screen Not Working or Black

Try a hard reset. Take out all the batteries, and while putting them back in, hold down the "DEL" key. Then, turn it back on and you can adjust the contrast by pressing the "2nd" key and the down arrow at the same time. I just got this info. online and it finally worked for me...good luck!

SOURCE: How do I increase the screen brightness on my TI-85 calculator?

push the 2nd key and then the up arrow.
Jon

SOURCE: No decimal display on TI BA-II calculator

Your BA II PLUS stores numeric values internally to an accuracy of 13 digits. However, the numbers it displays depends on the number of decimal places to which you have it set (choice of 0–9 or floating decimal). To set the number of decimal places displayed to three: hit [2ND][FORMAT][3][ENTER]This setting also continues indefinitely (even though the calculator is turned off and on) until it is changed.

SOURCE: My TI-nspire CAS doesn't want to go on! I changed

Hello,
Try the other recipes from the TI knowledge base concerning a calculator failing to turn on

For the TI-Nspire™ Family:

1. Remove thekeypad (for TI-Nspire) or the battery door (for TI-Nspire CAS) andremove at least 1 battery from each column of batteries. After 2-5seconds, reinsert the batteries and turn the unit on. This will causethe unit to reboot the operating system.
2. Remove the keypad(for TI-Nspire) or the battery door (for TI-Nspire CAS) and remove atleast 1 battery from each column of batteries. After 2-5 seconds,reinsert the batteries and LEAVE THE UNIT OFF (do not turn on and thenback off). Hold down [Home] [Enter] [P], and while holdingthese keys, press [On]. The device will boot up as in the previousreset, but will display a menu with the following options. Please tryoptions 1, 2, 3, and 4 in that order. ** The [Home] key is located atthe top right of the TI-Nspire keypad and has a picture of a house onit.

SOURCE: My TI-nspire CAS doesn't want to go on!

Hello,
Here is what the TI knowledge base says about a calculator failing to turn on.

For the TI-Nspire™ Family:

1. Remove thekeypad (for TI-Nspire) or the battery door (for TI-Nspire CAS) andremove at least 1 battery from each column of batteries. After 2-5seconds, reinsert the batteries and turn the unit on. This will causethe unit to reboot the operating system.
2. Remove the keypad(for TI-Nspire) or the battery door (for TI-Nspire CAS) and remove atleast 1 battery from each column of batteries. After 2-5 seconds,reinsert the batteries and LEAVE THE UNIT OFF (do not turn on and thenback off). Hold down [Home] [Enter] [P], and while holdingthese keys, press [On]. The device will boot up as in the previousreset, but will display a menu with the following options. Please tryoptions 1, 2, 3, and 4 in that order. ** The [Home] key is located atthe top right of the TI-Nspire keypad and has a picture of a house onit.