powering up is it a bad idea?

[xwarp]

if it is a "powerstat" brand autotransformer type 21, this connections will be this:

for counter clockwise knob rotation:

terminal 4,5 = voltage input

terminal 1, 3 = voltage output

for clockwise knob rotation:

terminal 1,2 = voltage input

terminal 3,4 = voltage output

bill

edit: yes, an isolation transformer is good too.