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Assembling a new desktop computer

Last response: in Systems
June 20, 2010 5:37:28 AM

I am trying to build my first own computer. intel 41rq mb standby power led is on and mercury chassis power led is constantly on.but mercury power supply fan and intel pentiun dual core E5400 processor fan is not rotating. what is the problem.
a b å Intel
June 20, 2010 12:50:52 PM


The Corsair guy is right in that if the PSU does not power up the fans, the PSU is bad.

But the fans spinning up does not necessarily mean the PSU is good. All it indicates is that the PSU will provide some small amount of 12 volt power. You do not know if the 3.3 or 5 volt outputs work. And you do not know if the control signal, "PowerOK", is working.

Now, combine that with voltage measurements and you can be reasonably sure that the PSU is working - at least under no load conditions. Measure between the colored wires and either chassis ground or the black wires. Yellow wires should be 12 volts. Red wires: +5 volts, orange wires: +3.3 volts, blue wire : -12 volts, violet wire: 5 volts always on. Tolerances are +/- 5% except for the -12 volts which is +/- 10%.

The gray wire is really important. It should go from 0 to +5 volts when you turn the PSU on with the case switch. CPU needs this signal to boot.