Casio fx4000p repair question

[Tugdual]

(12-28-2022 06:11 PM)Dan C Wrote:  I have an fx-4000p also, but i have never actually figured out how the power switch works.
Not much help for you, but i assume you have seen these great pictures from jebem?

http://2.bp.blogspot.com/-9s28vY7K15A/Vm...0P_018.jpg

Full tread: https://www.hpmuseum.org/forum/thread-5278.html

Thanks Dan, yes I had seen these pictures and this is where I found I was missing that part. See the carbon film with 3 strips and a white dot? The the white dot is missing on mine and I wonder what it is made of. It seems to ensure that the main board is pressed against the carbon contact.

The whole switch is a weird choice it is simply a carbon film pressing the board and shorting two points on the main board in one position. I guess this is introducing a lot of resistance in the main power circuiit.