Unless something is leaking smoke, it's more likely you have an "open" than a "short".
By the era this tractor was made, things had already got QUITE complicated, there's a lot involved in the PTO safety circuit... operator presence switch, time delay electronic module, etc., too much to post here.
You need a factory manual with detailed troubleshooting instructions.
You can download a copy as a LARGE .pdf (over 900 pages) at this link:
Electrical starts at Page 220.