You should say "power centre" instead of "converter" so we don't get confused. The converter is in the power centre and just converts 120v to 12v.
Meanwhile you do have a ground fault somewhere in the rig, which is why he cut off the ground prong (it is not "broken" --he cut it off) instead of finding the problem and fixing it.
Meanwhile, don't stand in a puddle and put your hand on the skin of the rig. :(
Agree, if you are not familiar with electrical issues, get a pro to fix it. In a 1996 rig it could be anything, but the first suspect might be the shore power cord plug itself that he cut the prong off. Perhaps a new plug on that cord, that is properly connected to the three wires would fix it right there. You have to replace that plug anyway with a proper three-prong.
If not, it is a time-consuming task to find the ground fault in the rig, and time is money (100/hr?) so lots of motivation to try to find the problem yourself.
That gets you to the suggestion earlier to try one breaker at a time to narrow down which circuit is guilty. Then you can chase down what on that circuit is guilty. (But start outside with the shore power cord plug in case that was it and save a bunch of work checking inside the rig)