john deere stx38 won't turnover

I have a 1985 STX38 and while I was mowing one day, it shut down like I turned the key off. No power to anything. I was having trouble with the PTO kicking out before this happened if that tells you anything. I did find 2 wires that are not hooked anywhere. One is a black wire that is part of the PTO harness and the other is a black cable like a ground cable. Where should these be hooked? Thanks.