HP42S bug?



I was searching recently on the internet about the curve fitting bug in the HP42S, but haven't found any references...
It seems that, at least in my unit (1989, brazilian "A3" version, with the glass over the display), the FCSTX funcion doesn't work when used with the power fit mode (PWRF) selected: it isn't the inverse of the FCSTY one (but FCSTY works alright). I am curious to know if this bug is described somewhere else and if it affects other versions of this machine.

Iuri Wickert


Yes, this bug was documented. I believe 42s calculators then shipped with an addendum card describing a work-around. Not sure where to find that, however.



You're in luck. I have the addendum card here at work, taped to the blank Page 5 in my Owner's Manual. Good thing I checked the forum before I went home.

The addendum card is dated 12/88, and -- for those who care -- the reorder number is 00042-90042. It's a front-to-back half-size page, and it'a bit long to retype here. I will scan it to .pdf and make it available via e-mail. Please send me a request at my home email address (fel3@pacbell.net) and I will send it out to you. If anyone else needs a copy, please let me know.




To Iuri and anyone else who may have requested a .pdf copy of the HP-42S addendum card this evening, please send your request again. We had an e-mail glitch here at home and it appears that I lost several messages.



> ... the FCSTX funcion doesn't work when used with the power

> fit mode (PWRF) selected: it isn't the inverse of the FCSTY one

I think FCSTX must NOT be the 'reverse' (like you mean) of FCSTY, because the best fit line on the X direction is not the same as on the Y direction.

Yes, I know this is not clear -- just a starting point for those interested.

Take care.

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