A strange behaviour when my classic calculator is connected to a wall adapter

[Geoff Quickfall]

Yes, i am sure there is and electrolytic cap and as it fails to open it becomes a resistor limiting the voltage and current passed through it resulting in the lower voltage measured at the plug end.

Do let us know. And take some quick photos.

Ah, something to ad to the book, which I am working on during COVID, an appendix on adapters, I must have around 30 including some defunct ones to sacrifice to photos

Geoff