Try to find something newer. That head is around thirty years old, yes? It's got many aged, deteriorated parts in it (every cap., to mention just a few). I have a couple of them. I had one looked at and the cost to repair it was way above what it cost me, and, really not worth the bench-fee to open it up. Peavey doesn't offer much help on the parts, anymore, either.
Dirt cheap is right. If you really like them, find another, working one.
It's not the arrow, it's the indian!