Transformer burning out in an Evcon DES 80

[BigDave67s]

I have a Coleman Evcon D.E.S. 80, Model # 8975E676, in which the transformer keeps burning out.
Where should I look for a short or other current overload? What are the most likely places/items to be bad?

I'm planning on putting in an in-line fuse holder, with a 3A fuse, to protect the next transformer. Do I put the fuse on the primary or secondary side of the transformer?

Thanks