Power Supply !!!

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Tim

I am going to replace my power supply with a new one due
to certain problems. What wattage should I go for? Does
it make a difference whether I get a 300w or a 400w?
Please advise me on this.

Regards, Tim.
 
You need a power supply that will supply 120% of the load
required by the installed devices and those you intend to
add. You can figure 50 Watts for the mobo-75-100 W for the
CPU, 50-100 W for the graphics card, 25 w for each drive
plus any extras you have added such as lights. Each cooling
fan will draw 5 w, each USB device draws 0.5 w, you do the
math and allow some extra.

The power supply will only supply what the system demands,
but if the power supply is rated at 300 watts and you
connect 400 watts of draw, it will try to carry the load and
will over-heat. The load at start-up is highest as the
drives try to spin up to speed, so failing to boot is likely
with an undersized power supply.


--
The people think the Constitution protects their rights;
But government sees it as an obstacle to be overcome.


| I am going to replace my power supply with a new one due
| to certain problems. What wattage should I go for? Does
| it make a difference whether I get a 300w or a 400w?
| Please advise me on this.
|
| Regards, Tim.
 
What problems ?

Am just interested . . .

Are you aware that in a small number of cases replacing
the power supply will cause your Motherboard to fail ?
 
Strictly anecdotal from being an on-site support tech for
many years . . . Power supply output specs change over
time as internal components wear from heat, power cycling,
dust buildup, etc.

Introducing a new power supply to a motherboard, after a
period of years with a steady decrease in performance by
the original power supply, can sometimes be enough to blow
a capacitor or other component. I've seen this primarily
on Microstar motherboards . . .

It's not a high-percentage problem, just thought the user
should be aware of this particular risk factor . . .
 
Power supplies only output the demanded power. Unless the
mobo voltage regulator is defective or there is a short
already, the PS will only deliver what is needed. If the
"need" is greater than rated power, the PS will deliver that
amount until it burns up or blows a limiting fuse.
But the heads up on MicroStar mobo is useful, personally I
prefer other name brands.


--
The people think the Constitution protects their rights;
But government sees it as an obstacle to be overcome.


message | Strictly anecdotal from being an on-site support tech for
| many years . . . Power supply output specs change over
| time as internal components wear from heat, power cycling,
| dust buildup, etc.
|
| Introducing a new power supply to a motherboard, after a
| period of years with a steady decrease in performance by
| the original power supply, can sometimes be enough to blow
| a capacitor or other component. I've seen this primarily
| on Microstar motherboards . . .
|
| It's not a high-percentage problem, just thought the user
| should be aware of this particular risk factor . . .
|
| >-----Original Message-----
| >No. Please provide references.
| >--
| >Cari (MS-MVP Windows Client - Printing, Imaging &
| Hardware)
| >www.coribright.com
| >
| in message
| >| >
| >> Are you aware that in a small number of cases replacing
| >> the power supply will cause your Motherboard to fail ?
| >>
| >
| >
| >.
| >
 
It's about as likely as somebody leaving a screw loose on the motherboard,
scraping the motherboard with a screwdriver, or doing something else that
kills the motherboard.

As far as any bad capacitors you've seen, there have been a whole lot of bad
capacitors, and it has nothing to do with power supplies blowing them, just
a huge batch of defective capacitors. Could just be that a computer stops
booting, someone replaces the PS with a known good one, maybe a momentary
surge of power, and on inspection, there are bad capacitors. But...the
capacitors were probably bad all along.
 
A power supply outputting less voltage does not damage
electronics. That low voltage causing damage is urban myth
based upon anecdotal evidence that is not tempered by first
learning underlying theory and not learning how capacitors
fail.

But some power supplies can damage the motherboard. These
are supplies recommended, again, by those who fail to first
learn underlying theory. That theory says every power supply
must have overvoltage protection. A new power supply that
fails must never cause motherboard damage. But without
overvoltage protection - a function that was defacto standard
even 30 years ago - then a new power supply bought only on
price can damage rest of computer.

Notice what causes damage. Human who fails to learn
underlying theory, who fails to demand a long list of
numerical specifications for that supply, and who used a bean
counter mentality to obtain that power supply only on the
specification called price. Does that power supply
specifically state that it has overvoltage protection as
defined by Intel specs? If not, then we now know why that
power supply sold at a lower price.

What happens when a power supply is undersized? On power
up, supply will not provide the Power Good signal and computer
will not boot. A power supply that is undersized will output
a slightly lower voltage. The 3.5 digit multimeter quickly
identifies the undersized power supply even when computer
appears to be fully functional. Is power supply undersized?
That is why the informed computer assembler uses a 3.5 digit
multimeter.

Will a 300 watt power supply overheat if the computer
demands 400 watts? Of course not. Properly purchased power
supplies contain overpower protection. Will a properly
constructed power supply be damaged if all outputs are
shorted? Of course not. In fact, Intel even defines how
large the wire must be to short all power supply outputs - and
the power supply must not be damaged. Just two more myths too
often promoted by computer assemblers who failed to learn
underlying concepts.

The point is that every power supply must first meet a long
list of specifications. Specs that too many computer experts
neither understand nor bother to demand. Anecdotal evidence
alone to explain how capacitor failure happens is wrong. One
must first learn the underlying theory which means that long
list of specifications with numbers is comprehended. What is
a common source of computer failure? Human who fails to first
learn lessons from generations of experience. Top of that
list is to first learn the underlying theory and basic
electrical knowledge.
 
Does not make a difference if you are not planning to add drives or USB
devices.

If you are planning to exapnd you PC later (adding drives or USB devices)
then it would make sense to go with the 400w now, instead of later when you
find out that your system will not boot with your added devices.

Also, I would not trust any of the generic, noname power supplies that may
be available. Consider buying a brand-name power supply (like Antec or
Enermax) if possible, These are made better and have a longer warranty.
 
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