You can try

    require 'iconv'
    myEncoding = 'iso-8859-15' # or 'CP1252' or what you have
    s1 = '
    s1 = Iconv.new('utf-8', myEncoding ).iconv(s1)

Maybe, you will need the "Byte-order mark". That are 3 special Bytes
at the very beginning of your utf8-file:
wikipedia.org > utf-8 > "Byte-order mark"