HP 15C All segments on

[howardlong]

Folks,

I just received an HP 15C supposedly in full working order from an eBay seller. It arrived with no cells installed, so I inserted three brand new ones.

As soon as the cells are inserted, and before pressing any buttons, the display came up with all segments on, including annunciators.

The keyboard is apparently unresponsive, and I cannot turn off the display without removing the cells. Not even the On button does anything.

I've tried the shorting method a number of times after removing the cells to remove any residual charge, and measured that the charge has reasonably dissipated to a few mV. Presumably there's a capacitor in there to try to maintain the device's state while you change batteries.

On one occasion after discharging, when inserted the batteries the display came up blank instead, but following the same procedure again I am back to all segments on.

Does anyone have any recommendations or suggestions?

Many thanks, Howard