electrical/voltage spike problem

I have a 83 tercel that keeps burning out the voltage regulator, we brought it in the shop and 2 guys said it was fine, so they just cleaned it up and gave it back to us, then we put it on drove it for about a week and the same thing happened, so we brought it back and this time they put a voltage regulator on the alternator instead, so we drove it for about 2 weeks and the same thing happened, so then we brought it back and burned that one up too, we did that about 2 more times and the same thing happened, we've tested everything on that car and could not fine the problem, anybody got any ideas?

check wires, could be shorting out.