Ralph Shumaker wrote:
I notice that you did not mention anything that draws much of a load.
When I was in computer repair, I recall having *some* power supplies
that would not give the OK signal to the motherboard if there was not
enough of a load. I ended up having to have a hard disk drive plugged
into the power of the power supply to give it enough of a load. I
didn't connect the data cable, not for the most basic test. But I
always connected the power. Several motherboards that otherwise would
not POST, suddenly came to life, simply by giving enough load to the
power supply. Weird.
Actually, that's normal for most switching power supplies (which PC
supplies are). On a switching supply, there's generally a couple sense
lines that connect to the output and detect when current is being drawn
from the supply - when a load is connected. In simple terms it's part of
how they regulate the output.
On PC supplies of the type you refer to, there is a "Power Good" line
that serves this purpose that connects to +5V on the MoBo. In addition,
they need to have a load on them large enough to draw enough current so
they can regulate power efficiently and not burn up.
Also of note with most PC supplies, they can not provide the power they
state they can, and if they can they don't do it well. The only ones
that really can are those that cost more than double digits. Those that
are supplied with the $100 cases are pieces of crap. I can't tell you
how many PC supplies I've placed on a load bench and found they couldn't
regulate worth a damn and at rated output, would drop the voltage like
mad (not to mention the noise they started to supply).
One of the best things you can do for your system is spend the money on
a good power supply.
PGA
--
Paul G. Allen, BSIT/SE
Owner, Sr. Engineer
Random Logic Consulting Services
www.randomlogic.com
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[email protected]
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