Those MkIII/IV scrapers are certainly riehl hard to work on. Out of 5 or 6 lots I've only got 2 going. I try to make sure there's an encapsulated IC amongst them, which invariably do work. He doesn't seem to have these any more though.
Get yourself an unopened MkI/II. I'm sure you'd get one of these fired up in no time.
Rgds.