HP41 bugs - testing


Hi All, are there comprehensive test steps written down somewhere to determine which bugs a 41c has ? If so, can someone point me to those please ?



You should have been there (when the HP-41C was launched in 1979)!!


A full list is in "Extend Your HP-41" available on the DVD Version 7

Main versions:

ROM   Date codes   Comments
DDE 1926-1940
FDE 1936-1952
FEE 1951-2034
GFF 2035-84??
HFF 84??-Present CV version
NFL 2329- Present current CX version

John, if you scroll to to the bottom here you see the range of serial numbers which have specific bugs.

A simple test to see if you have most/all bugs is the following:
49, Sto 00, SF IND 00

If the Bat-indicator goes on you have bug 3 and hence most likely all other bugs as well.



Edited: 3 Mar 2010, 11:48 p.m. after one or more responses were posted


For bug 1:

48 SIGMA+ LASTX ... if 48 is not displayed, it has bug 1.

For bug 2:

999 ENTER 3 STO IND Y.... if this works, it has bug 2.

For bug 3:

49 STO 00 SF IND 00...if the BAT indicator turns on, it has bug 3. Note: this is 49, not 59.

BUG 4 is bad results from SIN for small angles. Can't remember the arguments.

The information below is from http://www.finseth.com/hpdata/hp41c.php

#4: Early models compute the SIN of small angles incorrectly.

#5: CLP would only clear 1089 program lines.

#6: -67A/-97A prorams that contain combinations of number entry, EEX, and CHS do not translate correctly. Example:


translates to


instead of

1E-7 -5

#7: The second nybble of the seventh byte of Alpha is copies along
with the first six bytes during an ASTO.

#8: Early machines do not decompile programs if they are turned off
during PRGM mode.

#9: Executing CAT 1 while in PRGM mode, then interrupting it with R/S causes step labelling oddities.

#10: If flag 25 is set and MEAN or SDEV causes an overflow, some flags can be altered.

#11 (CW1): If a program at the end of CAT 1 is replaced or deleted, a return to that program will return into the new program or off-program memory.

#12: On early models, the function LN(1+X) gives wrong answers for
values of X between -.9990234374 and -1.00.

#13: On early models, the operation (.1)^-43 gives an answer of
9.999999999E42 instead of 1E43.



And to know we paid sooo much for such faulty machines. I feel cheated by HP. <wink>



Thanks All,

I have a 1954 serial number, with the "tall keys".


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