HP 41-C Petroleum Fluids Pac


I have an HP 41-C with the Petroleum Fluids Pac and I'm thinking of selling both on e-Bay but haven't seen the PF Pac for sale alone nor with a calculator. Does anyone know if the PF Pac is scarce or in demand? I'm really curious.



The PF Pac is not on demand. The Math, Stat, and Math/Stat modules are the most common modules. Other less common modules are Financial, Survey, and Circuits. You can place the PF Pac for sale alone first. If it sells then fine. If not, include it in an auction with the HP41C.



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The Petrolium Fluid module includes advanced unit management routines - interesting for HP41 enthusiasts. Refer to the book "Expand your HP41" from Wlodek...

Regards - Chistoph Klug


There are several others out there. In the last two months I have repaired three HP41CX machines all with fluids pacs in them. My battery store referred the first guy to me, he referred the other two. All were VERY glad to get their machines humming again.


You can also try to sell the PF pac here on this website and sell the calculator on eBay.


The PF module appears with some regularity on eBay (often combined with a calculator), going for about $50 or more. You might try and advertise it on this site. I sold one here last summer, and received about3 serious offers. Factor in no listing fee or commision, plus the satisfaction of offering to a fairly select group of individuals that have helped to sustain interest in these machines.


Vicki, I second what Miki said. just because it is not advertised, don't think it is not in demand. Up to about six months ago, I was trying very hard to find one for daily use. I finally did, and I think the cost was about 50 dollars.

The pac does have the CON and INCON routines as someone mentioned. It is a cool feature. basically, you enter into the Alpha register the units you want to convert. For example, F-C would convert degrees fahrenheit to celsius. Then enter the number in (say 32) and XEQ CON. The X reg. shows you your answer. To convert back, XEQ INCON (inverse conversion I guess).

I do remember that when new (I was a young petroleum engineering student back then) the pack was more expensive that the Math or Stats pacs. If I remember correctly, it was about $75 or so. The others went for about 35-50 dollars.

Good luck!



You are right Jim, the original list price was $75. A friend of mine bought one second hand about 20 years ago for $100. They were in demand at that time among petroleum engineers. I bought one recently for $50 from Chris Catotti.

1234 to delete.


Thanks so much for the info you have shared with me. This is a great group of people !

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