HP-67 stuck in scientific (DSP 0) mode

[Roland57]

(11-02-2023 03:10 PM)Hiwi Wrote:  Hi,
i have another display problem, see picture.
My HP-67 is in very good condition and working well, however there is one part of the segment in the exponent sign permanently turned on.

Is this a problem of the display or driver IC? (Cathode or anode driver)
Has anyone seen this before?

The exponent and the normal sign are working as expected.

Ralf

Hello Ralf,
I had a hp67 showing this kind of "ghost segment". The reason was corrosion (coming from the battery compartment) on the main pcb. There was visible green dirt covering several traces of the pcb. This green stuff is conductive. After cleaning with IPA the ghost segment vanished.

Roland