rectifier converts the 70 odd ac volts down to ~14 dc volts , i would start with a new rectifier if its not controlling the voltage ,
the ebay mosfet type are much better than the original
eg
http://www.ebay.com.au/itm/Ricks-Hot-Sho...3f3e8c24d5
the ebay mosfet type are much better than the original
eg
http://www.ebay.com.au/itm/Ricks-Hot-Sho...3f3e8c24d5