SF-2 at Guitar Center

[Bob_Ross]

I doubt anyone at GC knows how to work one.

^^^This was how I stumbled upon mine ~25 years ago...shopping at the Guitar Center in Boston (back when it was on Comm. Ave. across from the BU central campus) I saw an SF-2 in the clearance rack and the sales dweeb literally said "If you can figure out what it does you can have it for what we paid for it"

[mica]

If the wrong polarity power supply is used the green light indicator will turn on but there will be no sound. There's a post in the FAQ about the choke (inductor) that blows when you use the wrong polarity for the unit.

Hum is a different (or one of several different) but repairable issue(s).