REPAIR HP 48S

[Pluscrafter]

I've found my HP 48, witch I've had learned programming 10 years ago, but today the calculator stucks, when I press the on BUTTON and the F Key. In won't react to any key press. Why is this happen? Could it be a rusty solder joint or something other and how can I open the calculator?

[radioFlash]

You can try resetting it using a paper clip. There's a small hole you can access under one of the plastic feet:
http://www.hpmuseum.org/cgi-sys/cgiwrap/hpmuseum/archv014.cgi?read=61858

The calculator is held together with heat stakes, so disassembly is a pain and once reassembled, it may not fit together quite right again. You can search for "how to open hp48" to find some instructions and videos.

[Pluscrafter]

The reset doesn't help and the calc freezes after pressing the on key.

Gesendet von meinem G8341 mit Tapatalk

[helius]

My experience with these units is that they frequently have poor contact between the keypad and the board. You can try holding gently below the display bezel and see if that makes the keys work. If it does, the problem is inconsistent pressure on the "zebra strip" of the keypad.

[SiliconWizard]

Here is  a web page that describes the disassembly of the HP48 (to upgrade its RAM, but you'll see how to open the case). http://www.datacomm.ch/grundsch/page_upgrade.html
Some pictures are missing but you should get the idea. Yes disassembling it requires drilling plastic rivets. Sucks. But if it's toast... you have nothing much to lose.

Could be anything from a dry solder joint, broken wire, rust, or even a bad ROM...?
Could also just be a stuck key.

[Pluscrafter]

The key works, but the calc(microcontroller?) freezes and you have to reset it.