AC355WL wood Lathe running slowly

Hiya. proud owner of the above lathe and it has given faultless service over the past 5 years. However, today I noticed that it was taking a rather long time to get up to max revs. Six months ago I changed the motor brushes and headstock bearings. The digital readout stopped showing revs last year and I changed the sensor and readout to no effect. Could this be a control box issue.