19 Dec
2015
19 Dec
'15
10:59 a.m.
On 12/19/2015 04:56 AM, Robert Jarratt wrote:
Actually, I may have just narrowed it down a bit. I connected a 12V DC bulb
to the -12 output, in parallel to a 15R resistor, and the PSU shuts down
immediately. The 12V bulb has a 21W rating. If my calculations are correct,
that means the bulb draws 1.75A. The 15R resistor would draw 0.8A. So a
total of 2.5A, which is well under the spec of 4A, but causes the PSU to
shutdown. Using the 5W filament of the bulb does not cause the PSU to shut
down.
Is there a flaw in my calculations, or am I really not overloading the -12V
supply? Just to recap I had a 15R resistor and a 12V DC 21W bulb in
parallel, on the -12V output.
Cold light bulbs draw WAY more current than when the
filament is hot. Not sure if a 21 W 12V bulb could draw 20
A cold, but it might.
Jon