Casio FX-850P question

Hi,

I hope this group is not totally dead.

I have a Casio FX-850P calculator (actually, the labelling says:
"personal computer") which I bough sometime in the 80's. It works, but I
have a little problem:

If I press the red button on the right hand side labelled "BRK (ON)" it
sometimes switches off.

Not always. I used the "P" hole on the back that I think does a full
reset: previous to that it switched off always.


Is this known?

I'm happy to RTFM, I just need to know the location of that "M" :-)

Or google, but I don't know what string to search for.

--
Cheers,
Carlos E.R.