daviddschool said:
It is interesting that you mention this because when I disconnect the
data cable, I was still hearing the whirring up and down of the drive
and I thought it was odd. I don't have the know-how to use a
multimeter on my computer.
More interesting is that I am using WIN 7 on a 1TB drive right now on
the machine. This drive was unusable a little while ago, but seems to
be fine now. My XP drive is unusable now - not sure why. And the new
drive I bought (which I have taken out of the machine), is sitting
waiting - hopefully still in working order. I don't have a new PSU
now, so it is really hard to test the whole setup.
OK, if you lack the skills to measure the power supply, do
you know how to change out the supply and test with another ?
Is the supply a standard ATX type ? The wire color code can
be found in one of the ATX specs. For example, in the third
spec, the colors for the main connector are on PDF page 37
(section 4.5.1).
http://web.archive.org/web/20030424...org/developer/specs/atx/ATX_ATX12V_PS_1_1.pdf
http://www.formfactors.org/developer/specs/atx/ATX12V_1_3dg.pdf
http://www.formfactors.org/developer/specs/ATX12V_PSDG_2_2_public_br2.pdf
Those specs are chronological, with the specs being for:
1) 20 pin main connector, with -5V still present on the connector.
Maybe you'd find those about 10 years ago. In some cases, the
power supply has -5V on it, but the motherboard isn't actually
depending on that voltage.
2) 20 pin main connector, with -5V removed
3) 24 pin main connector, with -5V removed
So one of those specs, could be compared to your main connector.
(Naturally, the color of the wires is the same on each one, on
the corresponding pins. It is not like they changed the order
of the colors on each one or anything. Each spec is a slight
tweak from the previous one. The 24 pin spec, adds 4 pins, without
changing the colors on the existing 20 pins.)
There is a page in each spec, which lists the wire colors on
the main connector. The wire color implies a certain rail
voltage in each case. If the wires weren't in a standard
color configuration, you might suspect a non-standard supply.
There was an era, when that was popular. Later, the main
PC manufacturers came to their senses, and started using
the same supplies everyone else (like home builders) did.
But it remains as a task for people doing computer repairs,
to verify that they're not dealing with that problem.
To replace a supply, all that is needed, is a screwdriver
for the four screws holding the supply. And a careful
methodical approach to removing it. The first time I did
it, I made diagrams of how everything went back. If the supply
is a standard ATX, then all you have to ensure in that case, is
that you have enough cables on the new supply, that the wires
are long enough. For example, say your old supply had two
cable runs for disk drives, with three Molex on one, and two
Molex plus a floppy connector on the other. New supplies will
be peppered with SATA power connectors, which may not be useful
to you. So you want to check that either the new supply
has more than two cable runs, of which two cable runs are
useful configurations. Or, perhaps, you get a power supply
with modular cabling, and verify that there are some cables
present which have the hard drive and/or floppy power connectors
that you need.
You can use the model number of your pre-built computer, and
either use a general search engine, or use Ebay, to search
for a replacement supply. If there is a match, you can be
guaranteed that any prospective vendor, will not tell you
whether the supply is standard or not. If it was standard,
you'd simply run away and find a supply which is cheaper
than the one they're selling. So don't expect technical
advice, from someone claiming to sell a replacement
for your computer. Even the original computer manufacturer,
may not offer any details about power supply type. They
want you to buy their overpriced product.
If you've already replaced the motherboard in the computer,
with a retail (home builder) motherboard, then that tells you
a standard ATX supply must have been in the computer case
already. If you have the original motherboard in the pre-built
computer, the manufacturer could do whatever they wanted, and
then you have to be more observant, to check the type.
Some power supply testers, may use a "window comparator" on
each rail for testing. For example, two analog comparators,
one set to 11.4V and one set to 12.6V, could be used to test
the 12V rail. Then, a logic equation,
"is voltage > 11.4 and voltage < 12.6 ?"
is evaluated, to control a LED which says whether that rail
passes or fails.
If the power supply tester doesn't make allowances for the
motherboard to be connected at the same time, then you're not
doing a "load test". You can't tell whether a power supply is
weak, unless some kind of representative load is present. That
is why using a multimeter can be a useful exercise. For example,
by connecting the black lead to a rear I/O screw (some have a
hole in the screw body, which will provide a place for your
meter probe), then connecting the red probe to the main wiring
harness, you can check voltages while the computer is running.
The main power connector has a nylon shell for the pins, but
there is exposed metal in each "cell" defined by the nylon shell.
You can touch the tip of a meter probe, on the metal within each
cell, while the computer is running. That is how you can verify
the voltages with a load in place. The connector is not so
carefully insulated, that you cannot get a measurement. I'm
convinced someone did that on purpose, because it would have
been easy to "super-seal" the whole thing up, so that
no meter probe could get in there, if they wanted. They could
make a molded connector, with little extra effort or cost.
So the current design, does seem to support measurement
while the system is running. You probe, where the wires
go into the nylon shell. And by holding only one probe in
your hands, you can make measurements with no risk of
shorting to the other probe.
I have a load box I built for testing power supplies, which
is how I can verify a power supply before I use it. That
would cost you anywhere from $50 to $100 for some power
resistors. Mine draws somewhere around 100W, and is not
intended to "crush" the supply or ruin it. An idling
computer may draw that much power. I let the supply
drive that load for a couple hours, and take measurements
at the end of the test, to verify the supply is OK. That is
how I test a new supply, if I buy one, without connecting
it to the motherboard. I place a fan next to the power
resistors, to help keep them cool during the test. I don't
expect everyone to rush out and do that, but that is
another alternative arrangement for testing.
HTH,
Paul
