In the end I discovered that the '1A'
fuse rating was marginal. The
PSU would work with one brand of 1A anti-surge fuse in the holder,
but would routinely blow a 1A anti-surge fuse of a different brand.
That took a _long_ time to sort out!
This is marked "1.6A MDL" and I have no clue what MDL is.
MDL is a slow-blo fuse, designed to take the "shock" of the inrush
current without blowing.