HP-15C strange key click sound

[Miki Mihajlovic]

Couple of keys sin, cos and to the lesser extent 1 and 2 have a strange click sound after that key is released. It is like the key on its way up drags some stiff plastic sheath which, after being released snaps and makes the click sound. Is there anybody else who had the same experience and knows or have an idea what it is and how it can be fixed. Have on mind that I never opened one of these calcs so some tips would be appreciated.

[Victor Koechli]

I've never heard such a sound, but a possibility is that some of the heat stakes that fix the keyboard PCB to the calculator front have become loose, and what you're hearing could be the PCB moving.

I'd open the calc and check. It's quite easy to fix, actually, the plastics that came off would be floating around inside the case...

Good Luck! Victor

[Mike Brady (San Francisco, USA)]

I have found the differences, in the keyboard's clicking sound, are attributed to changes in ambient temperature.