Power Supply Voltage Tolerances and Measurements
Posted: Thu Oct 01, 2009 7:19 am
Hello,
Recently i had a problem with the computer where it would shut down suddenly without
any warning. At first it happened once or twice, then it started to happen once a
day, then maybe twice a day, etc., until it started happening almost any time.
It even started to happen when the computer was first powered up in the morning,
and it would start to turn on and then immediately turn right off. Sometimes it would
wait until it started to boot first, then turn off, but other times it would make it
through the boot and then later turn off. I figured that since it could turn off
immeditately after turn on sometimes that it was probably the power supply caps
failing and it was detecting a fault condition and powering down, and other times
just barely passing which allowed boot up. Anyway, i decided to try a new power
supply first and work from there.
I took a trip down to the local computer shop and found a power supply that was
appropriate and the price was $49 USD and they had a nice big case there too for
$59 USD that came with the power supply. I decided to go with the new case because
of the similarity in price to the new power supply plus the old case has a power
switch that was sticky and so getting a new case would fix that problem too.
Ok, so now i am home and have everything changed over like the motherboard and
hard drive. I boot up and notice that the power supply voltage levels are a bit
different than with the old power supply. The older power supply had voltage
levels a little higher except for the Vcore which was a tiny tiny bit lower.
Anyway, my main concern was with the +12v supply which was considerably lower than
with the previous supply. It was down to 11.26v while the old one was 11.71v.
The new PS will also load down a little to as low as 11.14v which is quite a bit
under spec (the spec being 11.40v minimum). The +5v supply is just barely over
the min being 4.78v while the minimum is 4.75, but at least it is within spec.
It's the +12v supply that has me wondering if this supply is good enough for the
system.
I checked the rating of the power supply and the +12v line is rated for 2 amps
above the recommended requirement for the motherboard.
What i didnt know was the spec on the measurement system used to measure the +12v line,
which came with the motherboard system of course so i decided to measure the power
supply lines with my best meter. The measurements were quite surprising:
The +12v line measured +11.82 volts, and the +5v line measured 5.02 volts.
These two measurements basically say that the power supply is operating within spec,
and that the measurement system used by the ASUS motherboard is not as good as it
could be, measuring everything a bit low.
The measurements with the meter were all at the end of an unused hard drive cable
and compared with the ASUS software measurements at the same time.
I thought i would let everyone know about this.
Comments welcome.
Recently i had a problem with the computer where it would shut down suddenly without
any warning. At first it happened once or twice, then it started to happen once a
day, then maybe twice a day, etc., until it started happening almost any time.
It even started to happen when the computer was first powered up in the morning,
and it would start to turn on and then immediately turn right off. Sometimes it would
wait until it started to boot first, then turn off, but other times it would make it
through the boot and then later turn off. I figured that since it could turn off
immeditately after turn on sometimes that it was probably the power supply caps
failing and it was detecting a fault condition and powering down, and other times
just barely passing which allowed boot up. Anyway, i decided to try a new power
supply first and work from there.
I took a trip down to the local computer shop and found a power supply that was
appropriate and the price was $49 USD and they had a nice big case there too for
$59 USD that came with the power supply. I decided to go with the new case because
of the similarity in price to the new power supply plus the old case has a power
switch that was sticky and so getting a new case would fix that problem too.
Ok, so now i am home and have everything changed over like the motherboard and
hard drive. I boot up and notice that the power supply voltage levels are a bit
different than with the old power supply. The older power supply had voltage
levels a little higher except for the Vcore which was a tiny tiny bit lower.
Anyway, my main concern was with the +12v supply which was considerably lower than
with the previous supply. It was down to 11.26v while the old one was 11.71v.
The new PS will also load down a little to as low as 11.14v which is quite a bit
under spec (the spec being 11.40v minimum). The +5v supply is just barely over
the min being 4.78v while the minimum is 4.75, but at least it is within spec.
It's the +12v supply that has me wondering if this supply is good enough for the
system.
I checked the rating of the power supply and the +12v line is rated for 2 amps
above the recommended requirement for the motherboard.
What i didnt know was the spec on the measurement system used to measure the +12v line,
which came with the motherboard system of course so i decided to measure the power
supply lines with my best meter. The measurements were quite surprising:
The +12v line measured +11.82 volts, and the +5v line measured 5.02 volts.
These two measurements basically say that the power supply is operating within spec,
and that the measurement system used by the ASUS motherboard is not as good as it
could be, measuring everything a bit low.
The measurements with the meter were all at the end of an unused hard drive cable
and compared with the ASUS software measurements at the same time.
I thought i would let everyone know about this.
Comments welcome.