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  1. #1
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    TI-83 calculator can't power off. Need help please!

    I searching for TI-83 calculator schematics, but nothing found.

    The issue: When I insert batteries into calculator and power it on....OK! But when auto power off or 2nd/off pressed the screen contents disappear and the screen remain light grey. Current consumption is 20mA when power is off and 30mA when power is on.
    If power is on then all function is OK and selftest OK.

    Thank You!

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    Re: TI-83 calculator can't power off. Need help please!

    It's likely there is a component (not a relay) which turns current to the calculator On and Off. It might be inside an IC, or it might be discrete on the pcb.

    The component could be a mosfet. The gate is easily perforated by high voltage. This usually ruins the mosfet. So your calculator may turn on, but not shut off completely.

    QUESTION: What happens immediately after you insert batteries? Does the screen stay dark, or is it grey?

    Perhaps a high-voltage spike came through the battery contacts accidentally?



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    Re: TI-83 calculator can't power off. Need help please!

    When I insert batteries then happens nothing until "ON" key pressed. If powered on all functions OK. But when I press "2nd""Off" then screen is erased and remain light grey. If press "ON" again then all Ok again.

    The calculator went trough on customs x-ray gate when arrived.



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    Re: TI-83 calculator can't power off. Need help please!

    1.
    Airports tell us their security x-rays 'are safe' for passengers' electronic devices. However some people report their devices did not work after being scanned.

    2.
    When a calculator misbehaves, some instructions recommend that you do a total reset by pressing a certain button at a certain time. Or by removing batteries for several minutes. Etc.

    3.
    In case the screen driver is at fault...
    From what I read, the liquid crystals generally operate on an AC waveform, and a DC waveform at certain times. The AC portion must be centered around 0V, or else it shortens the crystals' life. (My information may be outdated.)
    Since you state the screen remains lit, then it could be receiving a bad waveform. This is not easy to verify nor fix. Nevertheless a meter might reveal a bad voltage at some component.



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    Re: TI-83 calculator can't power off. Need help please!

    Airports tell us their security x-rays 'are safe' for passengers' electronic devices. However some people report their devices did not work after being scanned.
    It is, I believe, more commonly the metal detector is the culprit to be blamed.

    The low frequency AC used by the metal detector can induce eddies on the electronic devices and can damage them. The metal detector in the frame has considerable power and can damage electronics. The handheld device can damage watches sometimes (I am told).

    In the present case (I think, as you too have suggested) the power on fet is likely to be at fault.



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    Re: TI-83 calculator can't power off. Need help please!

    I tried to find these smd part codes
    D3L 48(?FET) and RJ471A (Switching supply)
    Click image for larger version. 

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    - - - Updated - - -

    Sorry for my mistake! I pressed the big IC on top right and the calculator works again. Then I resoldered it and working.
    But here a picture:Click image for larger version. 

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ID:	149617

    Thank You!
    Last edited by jamespond; 21st October 2018 at 15:17.



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    Re: TI-83 calculator can't power off. Need help please!

    There's the word 'dropped' in your photo name. And the plastic enclosure appears discolored as would happen from an impact.
    So this is one of those times you 'accidentally' fixed it? Fortunately we get lucky sometimes beat the system.


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