w_tom

On Aug 16, 2:25 pm, "Spirit" <no...@notthere.net> wrote:
> Actually for a power supply to cause problems the voltage can be
> low or not clean enough of a wave length (tough generally computers
> are fairly forgiving of either of these issues). High voltage or a high
> forced amperage can also cause issues, especially spikes.

Power supplies must maintain perfectly in-spec power even when AC
mains voltage drops so low that light bulbs are only at 40%
intensity. Even Intel specs for power supplies make that demand.
That is another function of power supplies - to make AC power problems
irrelevant. But again, when computer assemblers only buy on dollars
and watts, then dumped into the market are many supplies missing those
required functions.

Let's look at the output of a computer grade UPS when in battery
backup mode. That 120 volt modified sine wave is ... two 200 volts
square waves with up to a 270 volt spike between those square waves.
Is that clean electricity? Of course not. Why does that one UPS not
cause computer problems? Again, power supplies make such power
problems irrelevant. That is required.

That UPS outputs power so 'dirty' as to damage some small electric
motors. Same electricity is perfectally acceptable to properly
constructed computers. Just another function that must be inside that
power supply.

However we don't let such power problems remain. For example, if
wall receptacles are installed with wires pushed into the back, then
intermittents can occur that exceed power supply functions. Whereas
'push in the back' wiring is acceptable for lights, it is completely
unacceptable for computers. A quick inspection by removing receptacle
cover plates will confirm good wiring wrapped around and secured by a
side mounted screw. Using the screw to clamp wires is important so
that power supply can make other electrical problems irrelevant.

But when a supply is failing, the computer may still boot. Only way
to find that failure is using a tool so ubiquitous as to be sold even
in K-mart, Sears, Radio Shack, Wal-mart, hardware stores, Lowes, etc.
That 3.5 digit multimeter costs only $20 - less in Wal-mart and when
on sale. Two mnutes with the meter means previous posts were
unnecessary beause meter numbers are so definitive - not subjective..