😟 i have burnt out two sail winches type

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=121173284235 they both got got caught around the main spline (came off the drum) have opened them up and found all ok except circuit bourd power in nothing out i took a bourd for a 90 degree servo and soldered that to the potentiometer and and was working well in rig on the bench put in the boat and now stopped can any one help we ideas as to what im doing wrong thanks mark