Travis,

Thanks again. Yes, I can do the math and understand ohm's law... and your
75% efficiency number seems about right (I assumed 80%) and consistent with
the fuse sizing, but the piece I missed in the spec sheet is the maximum 3A
in rush current. Where was this specified?

I think you've hit upon why the part exploded and burned up. It appears it
was indeed undersized for the application. So from their listing, which
part has the higher in rush current limit? Again, I did not see this
specified in the part list table. Thanks in advance.

Bob S

"Travis Jordan" wrote in message
m...
If it is a 600W non-PFC power supply we might assume at 80% efficiency
the input power to be somewhere around 750W.

750/120 = 6.25A (sound familiar) - full power operation.

Per Ohm's Law: 5 ohm starting resistance = 31W if starting inrush is
100% of full power load (not likely).
.18 ohm ending resistance = 1.125W at full power.

Note that the inrush current limit for the 5D-9 is only 3A, so either
you don't have a 600W supply or (most probably) the max starting surge
is calculated at 50% of the full power load or perhaps as you stated the
device is underrated. You decide.