Archived from groups: microsoft.public.windowsxp.hardware (
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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.
Mousey Mick wrote:
> 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 . . .
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