What is the exact nature of your concern? Do they still owe you more money?
If you sign a receipt for the check, then most likely that's an appropriate action. However if they're asking you to sign a release form indicating that they don't owe you any additional money, that is a whole different scenario.
What is it you're being asked to sign? Is it a release from their having any further financial obligations or is it a receipt saying that your received your check?
If you don't sign a simple receipt of a check, then you are keeping yourself unpaid and not accomplishing anything worthwhile legally.
However, if you have a legitimate complaint that you deserve additional pay ... such as for overtime, or unpaid hours, sick pay etc., then you should conduct matters differently...such as filing a written grievance to Human Resources/Personnel Dep't, and/or contacting a lawyer or Labor Board.