I have a janome that went through this- slowed right down to seeming like it just couldn't make another stitch- I took it back to the shop- they said it needed to go back in for 'warranty work- and sent it off- 2 weeks later it is back- no real explanation- but they seemed to have dealt with the issue- if you are still under warranty I would be sending it in- it has nothing to do with your 'power' source- it is something wrong with the machine.