HP-19c almost works

[teenix]

(11-17-2021 08:26 AM)Jonas Sandstedt Wrote:  A couple of months ago I acquired an HP-19C that needed some overhaul. It now functions normally when the printer is in “MAN”. The settings “TRACE” and “NORM” both function as the setting “NORM”, and when any one of these setting is chosen, the calculator will not calculate more “advanced” calculations such as sinus, logarithms and y^x, while "ordinary" calculations such as addition, multiplication, squares etc. work. When pressing for example 15 SIN, the printer prints “15 SIN” but with the result 15 on the display. My theory is that the printer motor somehow creates a disturbance that affects calculations that take longer time, such that they are not completed. Has anyone encountered such a problem, and/or have any tips how to approach it?
The calculator is powered by 4 AA NIMH cells.

Best regards
Jonas

The HP-91C has some transistor logic to expand the functions of the flag input to the ACT. Part of those functions are for the printer switch. Maybe one of the transistors is faulty.

cheers

Tony