Had the same problem, replaced the large cap on the main board. You need to take all the knobs of and unscrew the switches to get to it. It is a 470uF 25V 85°C AXIAL ALUMINUM ELECTROLYTIC. Works great now. Good luck.
JerseyMatt, Did you get it fixed? If not, I could do the work on it. I still have my Sov with multiple coils, so I can test before opening. Let me know.