Which version of the 120 is it ? Some years back , Rick Matte of YS( then a separate company) posted trouble shooting techniques for the 120 versions and the 140 FZ. I have a copy somewhere .I believe he now works for Airtronics. Check out NSRCA.org ( pattern association ) and also post this question on the pattern forum on RCU. Remember to say the version- NC, AC, SF, FZ , etc.