HP-67 stuck in scientific (DSP 0) mode

[Helix]

(07-17-2020 08:06 PM)tribidouille Wrote:  Then the HP-67 is broken?

Stupid question, but are the batteries in good state and fully charged?
Also, dirty contacts under the ON/OFF and PRGM/RUN switches can cause very strange behavior. I had such an experience with a calculator whose PCB was very dirty.
So, try to clean the PCB under the switches, and then put silicon grease, or better dielectric grease:
https://www.hpmuseum.org/forum/thread-13159.html