Found Electical Problem. Need Help

[BCReefer]

A few weeks ago we discussed why my GFI keeps on tripping. I now believe that it is caused by the 2 30W actinics/transformer. This morning with only that one transformer plugged in, my GFI would blow. I then unplugged it and plugged in everything else, turned on the 175 W MH and it worked beautifully.

What test can I do to see if it the transformer, wireharness, connectors etc. at this moment I have it disconnected. Should I bite the bullet and buy another transformer? The transformer is used and about 2 –3 years old.

Thanks
Patrick