It might be more efficient to make the calculator perform
a self-test. Here is the procedure.
Verifying Proper Operation (Self-Tests)
If it appears that the calculator will not turn on or otherwise is not operating properly, use one of the following procedures.
1. With the calculator off, hold down the [ON] key and press [X] (the multiply key)..
2. Release the [ON] key, then release the [X] key. This initiates a complete test of the calculator’s electronic circuitry. If everything is working correctly, within about 25 seconds (during which the word RUNNING the display should show –8,8,8,8,8,8,8,8,8,8, and all of the status indicators (except the * battery power indicator) should turn on. If the display shows Error 9, goes blank, or otherwise does not show the proper result, the calculator requires service.
Tests of the calculator’s electronics are also performed if the [+] key or the [divide] key is held down when [ON] is released. These tests are included in the calculator to be used in verifying that it is operating properly during manufacturing and service.
If you had suspected that the calculator was not working properly but the proper display was obtained in step 2, it is likely that you made an error in operating the calculator. We suggest you reread the section in this handbook applicable to your calculation — including, if appropriate, appendix A.
If it needs repairs, contact FixThatcal.org
Here are some examples from the manual (there is overlapping in the first two screen captures)