[ARC5] regarding stacking surplus switching regulator modules

[Dennis Monticelli]

Actually DC/DC switching regulators are mostly non-isolated.  But the little
modules you see in surplus stores are often from the telecom industry which
is the chief user of isolated power and for good reason considering the huge
ill-defined ground loops that would otherwise result in a big telco central
office.

Do be careful about how high you stack them because they were not designed
for that.  Extra insulation in the case mounting area is a good idea and
also antiparallel diodes across the output to prevent inadvertant current
backfeeding.  No guarantee these supplies will all power up in the right
sequence and could easily force current into their slow-to-come-up brothers.

I had some Lamda 100V AC/DC bricks (isolated) that I tried stacking even
though I could not find a hard spec on their voltage floating ability.  I
did real well up to 400V and then blew out the "top" brick when I went for
500V. Like the hams say, "If your antenna survived the winter, it wasn't
tall enough!"

Dennis AE6C