How do I Choose the Right Power Supply?

  • Thread starter Thread starter Jeremy
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Jeremy

Hello. A few days ago the fan in my power supply started making weird
noises. The "whirring" sound of the fan would fluctuate like the fan was
slowing down. I talked to a man at CompUSA and he said the power supply is
going out. It's not even a year old!

The power supply is 300 watts and I would just buy a new one but I have to
think about the future: Right now I have an AMD Athelon for XP processor
with a cooling fan, 1 80 GB hard drive, an internal graphics card with a
cooling fan, an internal sound card, a CD-RW and an old CD-ROM I never use.
In the future, though I'm going to get a DVD burner (which will replace the
CD-ROM), an external Sound Blaster Extigy card, a new case with fans I'll
add, myself, a second 40 GB hard drive and an internal video capture card.
With all this, do I need to get a new power supply with a higher wattage? If
so, what wattage?

Here are my two BIG questions:

**How do I go about selecting the right wattage of power supply for my
needs?**

** Are there other points I need to consider?**

Thank you for any information you can give.

Jeremy
 
Hello. A few days ago the fan in my power supply started making weird
noises. The "whirring" sound of the fan would fluctuate like the fan was
slowing down. I talked to a man at CompUSA and he said the power supply is
going out. It's not even a year old!

The power supply is 300 watts and I would just buy a new one but I have to
think about the future: Right now I have an AMD Athelon for XP processor
with a cooling fan, 1 80 GB hard drive, an internal graphics card with a
cooling fan, an internal sound card, a CD-RW and an old CD-ROM I never use.
In the future, though I'm going to get a DVD burner (which will replace the
CD-ROM), an external Sound Blaster Extigy card, a new case with fans I'll
add, myself, a second 40 GB hard drive and an internal video capture card.
With all this, do I need to get a new power supply with a higher wattage? If
so, what wattage?

Here are my two BIG questions:

**How do I go about selecting the right wattage of power supply for my
needs?**

** Are there other points I need to consider?**

Thank you for any information you can give.

Jeremy
Click to expand...

There are lots of individual methods used for selecting the right
power supply...

Some people buy the best they can afford.
Some buy what will power the most "stuff" they can fit in the case
they're using.
Some will just jump up 50W with slightly faster parts.
Some will buy a junk power supply rated at 300W but only worth 200W
then think they need 400W when they still only need 300W.

Some want to run their power supply at only 70% of max continuous load
rating.

Some want an "over"-rated power supply with plans to swap in a
quieter fan for a silent system, instead of paying 2X as much for a
PSU marketed as "quiet/silent".

Some people use an online calculator which invariably suggests they
need about 150% of the power they actually do.

Some people believe false reviews that all Athlons use 12V for CPU
power, leading them to believe they need 18A on the 12V rail when they
have no idea.

Some people will buy a bigger power supply than they need because
they believe they'll someday buy a super-fast new video card that will
need a nuclear reactor hooked to it.

Which people are you?

Thinking about the future, buy a name-brand (manufacturer name) 400W
with a dual ball-bearing fan or two, with SATA drive plugs.
Sparkle/Fortron are one of the best values, but Antec, PC Power &
Cooling, Delta and others make good units too.

Or if you want to just replace the fan, if the present power supply
still works fine, that'd be the most economical and "green" thing to
do... no sense creating landfill when it costs less to reuse
something. A name-brand (fan manufacturer name-brand) dual
ball-bearing fan should last a long time.. likely the original fan in
your power supply was a cheap sleeve bearing fan.

If you wanted to replace the fan you'll need to determine how it's
connected, plugged or soldered. It may be easiest to just splice the
wires, soldering and heatshrinking the new fan leads to the old leads
or using a crimp connector, but be sure it's crimped good. Choose a
fan similar in rating to the current fan, or for "most" power supplies
a .12A-.16A fan is a good compromise between airflow and noise.


Dave
 
Jeremy said:
Hello. A few days ago the fan in my power supply started making weird
noises. The "whirring" sound of the fan would fluctuate like the fan was
slowing down. I talked to a man at CompUSA and he said the power supply is
going out. It's not even a year old!

The power supply is 300 watts and I would just buy a new one but I have to
think about the future: Right now I have an AMD Athelon for XP processor
with a cooling fan, 1 80 GB hard drive, an internal graphics card with a
cooling fan, an internal sound card, a CD-RW and an old CD-ROM I never use.
In the future, though I'm going to get a DVD burner (which will replace the
CD-ROM), an external Sound Blaster Extigy card, a new case with fans I'll
add, myself, a second 40 GB hard drive and an internal video capture card.
With all this, do I need to get a new power supply with a higher wattage? If
so, what wattage?

Here are my two BIG questions:

**How do I go about selecting the right wattage of power supply for my
needs?**

** Are there other points I need to consider?**

Thank you for any information you can give.

Jeremy
Click to expand...

Calculate Here
http://www.jscustompcs.com/power_supply/

Note that the calc comes out on the high side so even if your at say 450 a
400 will still do.

Zalman 400w
http://www.casecooler.com/za400waqupos.html

Lane
 
Jeremy said:
Hello. A few days ago the fan in my power supply started making weird
noises. The "whirring" sound of the fan would fluctuate like the fan was
slowing down. I talked to a man at CompUSA and he said the power supply is
going out. It's not even a year old!
Click to expand...

Power supplies are notorious for using cheap fan motors. Most use a 80mm
sleve bearing fan. You can easily replace it with a dual ball bearing
fan which will last much longer. Don't belive those who say lethal
voltages lurk in power supplies for days. Just leave it unplugged for
ten minutes before you open it. You may have to splice the wires
(usually black and red), but just a well twisted joint insulated with
electrical tape will work OK.

It is dangerous. You can easily cut your fingers on the sharp edges
of most PS covers!
The power supply is 300 watts and I would just buy a new one but I have to
think about the future: Right now I have an AMD Athelon for XP processor
with a cooling fan, 1 80 GB hard drive, an internal graphics card with a
cooling fan, an internal sound card, a CD-RW and an old CD-ROM I never use.
In the future, though I'm going to get a DVD burner (which will replace the
CD-ROM), an external Sound Blaster Extigy card, a new case with fans I'll
add, myself, a second 40 GB hard drive and an internal video capture card.
With all this, do I need to get a new power supply with a higher wattage? If
so, what wattage?
Click to expand...

You've already got the main power consuming devices: The CPU and the graphics
card. If your PS was OK and you don't plan to add more than a second HD and
fans, 300W should be OK.

As many have said, you can't count on the advertized rating of a PS for its
actual performance, but yours has lasted so far. I'd spend 5 bucks for a new
fan right now. Just don't let it run with impaired cooling.
Here are my two BIG questions:

**How do I go about selecting the right wattage of power supply for my
needs?**

** Are there other points I need to consider?**

Thank you for any information you can give.
Click to expand...

kony has hit on the main considerations.


Virg Wall
 
kony said:
There are lots of individual methods used for selecting the right
power supply...

Some people buy the best they can afford.
Some buy what will power the most "stuff" they can fit in the case
they're using.
Some will just jump up 50W with slightly faster parts.
Some will buy a junk power supply rated at 300W but only worth 200W
then think they need 400W when they still only need 300W.

Some want to run their power supply at only 70% of max continuous load
rating.

Some want an "over"-rated power supply with plans to swap in a
quieter fan for a silent system, instead of paying 2X as much for a
PSU marketed as "quiet/silent".

Some people use an online calculator which invariably suggests they
need about 150% of the power they actually do.

Some people believe false reviews that all Athlons use 12V for CPU
power, leading them to believe they need 18A on the 12V rail when they
have no idea.

Some people will buy a bigger power supply than they need because
they believe they'll someday buy a super-fast new video card that will
need a nuclear reactor hooked to it.

Which people are you?
Click to expand...

After all the discussions about power supplies, I remembered a unit
that came with a cheap case about three years ago. It was marked:
L&C Technology LC-235ATX. I had changed out the fan/motor a couple
of years ago, but paid no attention to the supply itself and had built
a new computer in a different case.

Just today I opened the unit to take a detailed look.
I was suprised to find how well it was constructed. It was labeled
"Deer" on the PC board, which is one of the most maligned supplies.
All of the electrolytics were rated at 105 degrees C., and the board
lay-out was very good.

I did not try loading it to the max currents, but the components
seemed to be well within the required ratings. The internal wiring
was well positioned with cable ties where needed.

I do believe "You get what you pay for.", but I think many pay
for "Monstor Cables" for their hi-fi, with gold plated RCA plugs,
and will insist they can hear the difference.

I don't know any way of checking for value, especially in an area
where brand names mean so little.

The computer field is one of the few remaining consumer areas where
you can find good value if you know how to look!

Virg Wall
 
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