[mythtv-users] Power supply for ATX

Brian Wood beww at beww.org
Sun Jan 21 23:46:33 UTC 2007

On Jan 21, 2007, at 4:13 PM, Bill Williamson wrote:

> On 1/21/07, Damian Surr <damian at gingermagic.com> wrote:
>> only see ATX2 and high wattage power supply's. I think the one  
>> that's in
>> there is 300W and I don't really want to go any higher if I don't  
>> have
>> to as I don't want it to drink electricity.
> Power supplies are rated on peak capacity, not power usage.  A 1KW
> power supply will not draw any more power than a 300W power supply
> hooked to the same computer, and may even draw LESS power as it will
> likely be more effecient.

True but incomplete.

The rating of a PS is the total of the various voltages, so you  
could, for example, overload the +12V output while still staying  
within the total wattage rating of the supply.

Add to that the fact that the manufacturers outright lie in a lot of  
cases and the rating of a PS can become pretty meaningless.

Then there are factors other than the voltage and current, like  
ripple, regulation, power factor and others. The result is that two  
supplies with identical "ratings" can be totally different animals.

Especially for a supply for a Myth box, which tends to be on all the  
time, the "power factor" and the overall efficiency should be taken  
into consideration.

It drives me crazy when I see an ad for a "600 watt supply - $19.95",  
but such things are common.

The bottom line is that good power supplies are expensive, and you  
get what you pay for. A good unit from PC Power and Cooling or  
Thermaltake will cost you up front but pay for itself in the end.

IMHO buy the best supply you can afford, you will never regret it.  
Power supplies are the most overlooked parts of modern PCs, and the  
cause of more problems than people suspect.

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