Hi Roger_S,
It's not working with J300 set to 1 and 2, because that selects TICK signal from the PSU (mains frequency). It "should" be working set at 2 and 3, though AC TICK is probably best.
Sorry if this is stating the obvious, but did you try re-seating all the socketed chips? (I once had an A500 with screwy video, re-seating Paula cured it.)
