Most all of the RCA's had three prong plugs. There again the fault was most likely not due to the receiver itself but to a mis-wired GFI outlet somewhere in that circuit.
Our leadtech (B.K.) called me once a week (or at least every other week) asking me to talk a tech through this sort of problem (he called me because I had worked for an electrician before getting into the sat biz).
Remember Jason J. from Grant? He blew 4 receivers on one job in a matter of ten minutes before calling B.K. (who in turn called me) about the problem.
The two prong adapters are a quick fix to the problem, but the thing is to detect the problem before it blows the receiver up in the first place. A good outlet tester that has the GFI test button on it is what is needed. Also, you will probably find this problem more in new houses than in older homes (unless new outlets or rewiring has recently been done in the older home).