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teenix · 11-17-2016, 12:07 AM

Hi all,

This chip seems to appear in the printer type calculators like HP-19C and HP-10

It seems to be a mystery. Anyone ever find out what it is for?

cheers

Tony

Dave Frederickson · (This post was last modified: 11-17-2016 12:37 AM by Dave Frederickson.)

According to the HP-97 service manual, it's a quad comparator used in the motor speed control circuit. See para. 2-28 for a complete description. The 19C schematic by Tony Duell identifies it as an LM339.

teenix · 11-17-2016, 04:59 AM

(11-17-2016 12:26 AM)Dave Frederickson Wrote: According to the HP-97 service manual, it's a quad comparator used in the motor speed control circuit. See para. 2-28 for a complete description. The 19C schematic by Tony Duell identifies it as an LM339.

Cool, thanks Dave.