Metspitzer said:
The correct answer was Power Supply. When I changed it with another
power supply, it started.
Every power supply I ever tested (less than a dozen) shows continuity
from hot to neutral. I assume this means the fuse is good. This
power supply shows no continuity from hot to neutral. I have
contacted Antec to see if it is still under warranty, so I don't plan
to open the case. (I think I ordered the PS from Amazon and it seems
that Amazon has lost it's order history)
The thing is, I can't explain how the fan rotated for an instant if
the fuse was bad.
If the fan "twitches", then you know the primary is intact, and something
is defective on the secondary. To "twitch", there has to be some
transformer action, between the primary and secondary. The switching
transistors on the primary, have to run for a short period of time,
to provide enough energy through the transformer, to make the cooling fan
on the CPU to twitch. The power supply has capacitors on the secondary side,
and they'd need to be charged high enough, to cause the fan motor to start
moving. So it's going to take thousands of switching cycles on the
switching transistors (maybe 35 milliseconds worth), to get that far.
*******
With respect to your testing the contacts on the AC side of the
supply, you'd need to understand how the multimeter does its test,
to understand the results.
For example, look at the primary here, and tell me under what
conditions the input will conduct. Hint - two diode drops into
a capacitor. Does the multimeter provide a high enough voltage
to cause two diodes in series to conduct ? You really need a
good understanding of how the multimeter works, before you
can understand the results. Some measurements are worthless,
because they can be ambiguous. (Double hint - just because
it reads open, doesn't mean its open. It's a function of
what the meter is doing. To remove the ambiguity, you
remove the power supply cover, and ohm out the fuse directly
if you can find it.) In this example, there is that 560K
on the primary side in parallel, and perhaps you can see
that one.
http://www.pavouk.org/hw/en_atxps.html
An ohmmeter is "a voltmeter, in parallel with a
current source with a limited compliance voltage".
And in English, it means the ohmmeter has two "corner
conditions". Into a dead short, the current source won't
put more than the current limit value into the circuit
(like, 1.000 milliamps of test current or 100.0 microamps
of test current). And when open circuit, the current source
voltage level won't rise to higher than the compliance
voltage level. (Perhaps that is 1 volt on a low power ohms range,
for example. My old Simpson analog meter, could apply as much
as 9 volts under similar conditions. My Simpson is the one
that's going to "find the fuse" for me.)
http://www.allaboutcircuits.com/vol_3/chpt_3/2.html
"Beware that some digital multimeters equipped with a "diode check"
function may output a very low test voltage (less than 0.3 volts)
when set to the regular "resistance" (ohm) function: too low to
fully collapse the depletion region of a PN junction. The philosophy
here is that the "diode check" function is to be used for testing
semiconductor devices, and the "resistance" function for anything
else. By using a very low test voltage to measure resistance,
it is easier for a technician to measure the resistance of
non-semiconductor components connected to semiconductor components,
since the semiconductor component junctions will not become
forward-biased with such low voltages."
That's an explanation of so-called "low power ohms" versus
"high power ohms" type measurements. The difference is the first
one, doesn't use a compliance voltage value high enough to turn
on diodes.
A great learning experience, is to connect two multimeters
together. For example, put one of them on "ohms" and the
other on "volts". Or, put one on "ohms" and the other
on "current" (after changing the holes the test leads go into).
The things you read out, should help you better understand
the stimulus the meter is applying to a circuit. And at
least explain, how two meters might reach a different
conclusion.
Paul
But in a 110 country, switching to 220