The 48V is sent on pins 2 and 3 (i.e. signal +ve and -ve) and 0V is connected to the mic
ground. Unless you have a short to earth within the SM57 then there won't be any
If you have only used dynamics before then also note that if
you've got any dodgy mic leads then chucking phantom power down them will show them up by
large amounts of crackles. Be prepared to replace some mic leads!
-------------------- Disclaimer: Any opinions expressed above do not necessarily reflect my true opinions, which remain the property of my wife.