Stu Gotts wrote:
Not really common knowledge and you could screw it up if you're not
careful. You need to take the actual digits out, then clean the
contacts with a good cleaner or maybe even alcohol. If they're not
bad, this will bring them back to life. It's takes a bit of patience,
but it's not brain surgery.


A pencil eraser is commonly used to burnish the contacts.

John Mireley