Does anyone know of a good book (or video) on sewing machine repair? I now have a lovely collection of four electric and one treadle machine whose tension is either off, or the bobbin thread pulls the top thread out of the needle. I'd like to be able to figure out how to fix them myself (or, through some miracle, talk my husband into learning how!), since we have one vehicle and my husband needs it during the hours that the sewing machine shops are open.