I've got a HP28C that hasn't been used for years. I've changed the batteries and run the self test. But it can't be switched on. Anybody knows what's the problem is? and how to deal with it?
I'll be grateful to hear from you.


How could you run the self test if you can't switch it on? If you mean you can't switch it _OFF_ then pls note that the on/off key is not a toggle, press Shift then ON to put it off (that's like M$: "press Start for shutdown").



That's why I couldn't understand why the screen was black when I pressed the on button.

But I've solved the problem now. Got a tip to short circuit the battery spring. It's working now.

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