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- Estimating Power Supply and UPS Requirements
- Gary Brown
May 15, 2007, 6:00 pm
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Is there a site that helps estimate safe power supply and UPS sizes?
The PC is on its third PSU in 4+ years. The second, an Antec 350W,
lasted less than a year despite my careful estimates from manufacturers'
Also, an APC 350 UPS was completely useless. It held voltage for at
most 10 seconds. Not time enough to shut down. I am not sure if it was
a bad unit or just inadequate for this system. It finally failed
FWIW, the configuration is:
ASUS A78XE MB
AMD 2800+ CPU
250GB SATA HD
400GB SATA HD
160GB EIDE HD
Radeon 9200 video card
Re: Estimating Power Supply and UPS Requirements
Do you have a CRT monitor and if so is it running from the
UPS (battery backup socket if not all are battey backed up)?
That will increase your UPS size requirement, as will buying
a lower end UPS. If the UPS battery is old it might just
need replaced, but generally I'd get at least a 500VA UPS
for a modern system, or higher if the monitor and other
peripherals were to run from it too.
I presume your motherboard is actually A7N8X (-XE?) which
uses 5V PSU rail to supply CPU power subcircuit on the
board. It means a good PSU for your uses would have at
least 200W of combined 3V+5V rating. This was more common
with older generations of PSU, a current generation PSU
would have to be significantly higher wattage to still
support that much 5V current.
So a website calculator would have to know that about your
motherboard in order to recommend the era of ATX spec you
needed, on an old ATX standard you might be able to use a
300W PSU but on current generation you might not even be
able to use some 500W PSU as most of those 500W are due to
it's capabilities on the 12V rail instead of 5V rail. Often
website calculators erroneously assume use of 12V current
for CPU power circuitry so I think you will not get an
applicable result from such calculators.
An example of a PSU that might work well for you is a
Fortron / Sparkle FSP400-60PFN The -60PFN part is
important, as Fortron does make newer PSU with less 5V, more
12V current as mentioned above.
However the Antec might have failed to a specific weakness
in it's capacitors, if it had different caps it might still
be working which isn't so much a matter of the wattage
rating, rather a [build quality] per wattage factor. If it
was the caps that failed, it might still be running if
higher quality caps had been used, but everything costs a
bit, most people won't pay more for a HQ 350W PSU as they
aren't informed of the difference for the money.
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