HP broken : help!


Hello, I need your help because my HP100LX is broken (I know, it isn't a true calculator but please, I really need some help....).

While it was connected to the external power supply it was overheat near the power connector and then it was off.
Now with the batteries all it's ok, but with only the external power supply it's all off.

I have opened it and I have found a smd component with a melted plastic case. It's the first component on the line from the power supply connector.

I can read that this component is a "15DM" in a SO23 case, but I don't know what kind of semiconductor it's, and how substitute it (possibly with an original replacement). I suppose that it's a diode to protect the HP by reverse polarity of the supply, but I am not sure.

Is there anyone who knows this component and where I can find it?

I can send you a picture of the pcb of the HP with the broken component.

Thank's very much for any help.

Best wishes,


(remove the double _nospam_ from my e-mail address)



Hi Claudio. By all means send me your photo.


It's a diode I guess. Nothing special about it, probably but it could be a Schottky diode. Knowing hp they may have used one.
Schottky diodes just turn on better (lower voltage drop and more quick turn-on) than regular rectifier diodes.

You can replace it with a IN 4001 rectifier diode or a UF4001
which is the high speed schottky version.

BUT, I'd get a circuit diagram or some help doing all this first.
After all your calc is still working, so far. What happened?



Hi Don and thanks for your reply.

I have sent the photo.



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