Thanks for the replies. I wasn't considering a repair, and the unit appears dead. It is a Sharp PW-9100 just for info. I have no idea of its history as it came in a large box of leads, wall warts, guitar tuners, cameras and vintage Japanese-to-English dictionary PDAs etc. These last included 3 unused Casio Ex-Word Dataplus 3 units. Probably worth zero these days but I will save one with my old calculator collection!
I will tear the Sharp to bits to have a look at the polariser etc just to educate myself.
Sorry, I missed the identical issue with the HP calculator!
Regards, BT