On Wed, 21 Jan 2004 19:29:47 -0500, w_tom wrote:

Assumed: a power supply can be damaged by too much load.
Not possible. In fact, Intel spec says how big a wire must be
to short together all power supply outputs - without damage.
That's right. All DC outputs from a power supply can be
shorted together and no damage may occur. So how does the
trivial load of that keyboard draw too much power?

Then a circuit limiting fuse on motherboard that provides
power to keyboard. Just another reason why keyboard could not
damage power supply.

The keyboard power is separate from main power, it is always on, and I
don't want to hear any friggin' more about how keyboard power "can't"
damage a power supply, when it most definitely DOES, and repeatably,
and demonstratably. The keyboard can draw 500ma, ATX spec calls for
720ma on 5v standby, almost all AT and cheap ATX supplies are only
rated at 200 or 300 ma, that can fail, often within a minute,
sometimes after a week or more, but it DOES, and only because keyboard
power is enabled. Drop by sometime, and I'll blow some power supplies
for you.... g

. Steve ..

Many 'bean counters' don't buy minimally acceptable power
supplies. Technical specs are simply irrelevant since price is
more important. Overseas manufacturers have discovered that
American computer assemblers are technically ignorant. So
they dump, at higher profits, supplies that can even be
damaged by load. If a keyboard is damaging a power supply,
then the problem is directly traceable to the North American
who buys that supply.

There is nothing new in these facts. Concepts are industry
standard for longer than PCs have even existed. Any
acceptable power supply is not damaged by too much load or a
short circuit of all outputs.

More myths - a plug-in UPS cleans power. Wrong. Power
connects directly to AC mains when UPS 'is not in' battery
backup mode. Where is the 'protection'? Furthermore a
plug-in UPS typically outputs its dirtiest power when 'is in'
battery backup mode. Power very dirty because any properly
selected power supply is not adversely affected by dirty AC
power. Electricity so dirty from this UPS that 120 VAC is two
200 volt square waves with up to a 270 volt spike between
those square waves. Electricity that could be destructive to
a small electric motor but is quite sufficient for a computer
power supply - because computer power supplies (properly
purchased) are so resilient.

The key phrase here is 'properly purchased'. Most power
supply problems are directly traceable to the human who got
the power supply they wanted. Price rather than value being
the reason for purchase.

Power supplies already have effective power conditioners -
internally. It is why that 200 volt square wave UPS output
does not affect computers. Increasing output wattage also
does not solve anything.

Every power supply listed by jbr sounds like classic 'dump
trash on Americans' power supplies - to increase
manufacturer's profits. If supply did not come with long list
of numerical specs, then, typically, it is a 'dumped' supply.
Such power supplies would be missing essential functions -
that means other computer parts would be damaged. Properly
purchased power supplies can not damage other computer
components. Just another function that those importers hope
North Americans don't know.

Why did those supplies fail? First, where are the long list
of specifications? No specs? Then supply probably performed
as manufacturer claimed. Then myth purveyors cite dirty
electricity, surge protectors, UPS solution, line
conditioners, and other nonsense. The supply was defective
when selected; a failure directly traceable to the human. No
long list of detailed numerical specs? Then assume the worst
- such as three failed supplies in one system.


"Steve(JazzHunter)" wrote:
I would like to hear JBR say "Yes, I checked the keyboard power
jumper." It may not seem a logical cause for repeated power supply
failure, but that is what actually happens. Until I discovered this
one computer would lose its power supply within two weeks, in one case
the supply lasted about a minute. I finally read the manual,
discovered the jumper, and the system has lasted since 2000. In
another case a store-built clone was losing supplies, when the second
one failed he brought it to me, sure enough keyboard power was
enabled, changed the jumper, and no more failures. Yes using better
supplies would help, but only to provide enough standby current.
That's why I'm chipping in with this suggestion, it doesn't appear
that others in this thread have encountered this issue, or have, but
don't know it.

Step one, check for this jumper, if it exists even, and assuming it's
a PIII, THEN move on to incoming AC. Logical?

Also I don't find that the supplies "degrade" usually it's the zener
shorting, a resistor overheating, or some such.