Remove invalid database characters on a file

Hi All -

I'm building a script wherein it is design to remove characters that are not accepted on a non-unicode database. Examples are the following: �,�,�,�,�, etc.

I can easily sed those characters one-by-one but I there's a problem when other unicode characters are found. Is there any way to remove all of them? I'm thinking they are all not found on a standard keyboard.

Please help. Thanks.

Also, I can't sed/grep characters with grave/accent like: �

this might help