hp 33c don´t turn off

[bernd scheurer]

hi,
i got a hp-33c in a very good condition (looks like new) via ebay. only one of the screw threads (in the battery compartment) was broken. so i fixed this little problem with glue. now i can use both screws.
but since this, the 33c don´t turn off. the on/off-button has no function. as soon as the battrypack is inside the 33c, the calculator is on. for turning off, i have to remove the batterypack.
selftest is positive an all parts (incl. on/off-slider und contacts) are in the right place!
does someone know this problem?

thanks for help or tipps.
kind regards
bernd scheurer

Edited: 9 Apr 2007, 7:25 p.m.

[Christoph Widmer]

Hi Bernd,
I had once the same problem on a HP 97. There the issue was that, with long time use, the slider had scraped some metal off the contacts of the printed circuit and deposited in the gap between the contacts for the slider - effectively making contact all the time. I had to open the calculator and remove the metal deposit between the contacts. Of course, I cannot be completely sure your calculator has the same problem, but this is my best guess. If you attempt a repair, first consult the detailed descriptions on this website for taking apart the calculator and then don't forget to put back some appropriate grease on the switch contacts, otherwise your PCB-contacts will be scraped off rather quickly.

Good luck and best regards.

[bernd scheurer]

hi christoph, thanks for your feedback and your ideas. i opened the 33c and found absolut clean contacts. after rebulid, the calculator doesnt work again. i think, it takes a lot more of time to fix this bug. thanks und best regards
bernd