Rhodes 88 Suitcase Piano Power

[isaacalfaro]

Hi, I'm new here and I can't seem to find what I'm looking for. On the Speaker Cab of my 88, for power, there is a male plug (both prongs the same size).
I'm using a 2 prong extension cord to plug it in and it works however, i have some questions. Do positive and negative matter on this amp? is there an upgrade kit to allow for a 3 prong (with ground)male?