The first sign of HP-35’s ln(2.02) bug

[Kretsh]

I owned one of the first manufactured HP35 calculators and received a certified letter from HP, just 1 or 2 months after receiving the calculator, alerting me to the computational bug: if e (epsilon) is raised to the 0.000200 exactly (or something like that) it would give an incorrect answer.

The letter stated, that if I could not "live" with this error, I could take it to my local HP center and they could change out the ROM chip with the corrected algorithm, at no charge. That I did as the HP center was just up the road in Dallas, from where I worked in Dallas. The ROM was swapped out and HP also changed the slider/button on the On-Off switch to designate the update. This new sliding button was only fractionally higher.

Kretsh
Ex-Texas Instrument Employee
1971-1974