# what should be the reading on the power_good/power_ok pin?



## jjbtnc (Aug 27, 2007)

hello - my old psu just failed on me a antec truepower 480w

I have 2 possible emergency replacements until i get a permanent replacement as the antec maybe under warranty.

1 is a Dell nps-250gb - 250w max - which amazingly for dell has the standard atx pin out so it will work with non dell motherboards - i've checked all the pins with a voltmeter.

2 - is a Dell nps-300gb - 330w max - which is a 24pin atx psu and as with a lot of dells has a non standard pin out - i've been through and checked all the voltages on the pins and i'm quite happy with moding the wiring to make it a standard atx connector.

Thing is i've double checked and double checked but looking at each psu's pin that corresponds to power_good/power_ok/pwr_ok/pwr_good (depending on how it is spelt) - they have different values

On the Dell nps-250gb the power_good pin is pin8/grey and it reads 5.14v - this is done with the psu not plugged in to any motherboard/pc components and with the green pin shorted to ground i.e. shorted to make the psu run without a motherboard.

Now on the Dell nps-300gb the power_good pin is pin5/orange and this is giving a reading of 0.02v again this is done by running the psu with no pc components and shorting the ps_on with a ground which happens to be pin13/grey as ps_on (don't forget this is a 24 pin connector so if pin1 is the bottom left of the psu connector then pin 13 of the psu connector is top left)

i realise the wiring is different which is why the nps-300gb will need an adapter to be the same as a standard 24pin atx connector - i have an adapter to fit a 24pin connector on to a 20pin motherboard (which is what i have - a asus a7n8x-e deluxe)

running the 24pin connector through the 20 pin adapter gives the same result - it's power_good gives a reading of 0.02v

so if i rewire the dell nps-300gb 24pin and then use the 20 pin adapter i will end up with a standard 20pin atx connector - the same as the nps-250gb EXCEPT one will have a value of 5.14v on the power_good pin while the other will have a value of 0.02 on the power_good pin

so.......one sounds like it's broken - which one is it? and what voltage reading should a psu be giving on the power_good pin?


hope somebody can help with this


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## dai (Jul 2, 2004)

these should cover all
http://www.tech-forums.net/pc/f77/how-measuring-psu-rails-130666/
http://www.techsupportforum.com/f210/test-your-power-supply-with-a-multi-meter-151526.html
http://www.endpcnoise.com/cgi-bin/e/std/sku=dellconverter
http://www.bluemax.net/techtips/ATXPowerSupplyWiring/ATXPowerSupplyWiring.htm


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## jjbtnc (Aug 27, 2007)

cheers dai - thanks for the links, i did search but i was looking for words like power good, power_good, pwr_good, power_ok etc etc - i thought that they would throw up any posts, my mistake.

i aslo found this after a bit of googling

http://www.informit.com/articles/article.aspx?p=31105&seqNum=2

and


http://www.scotsmist.co.uk/power_supply2.html#Heading6

http://web2.murraystate.edu/andy.batts/ps/POWER_OK.HTM

thought i'd post those in case somebody else is looking


So.....the lower wattage one does a self check and when it is happy that it's volatages are ok it puts out a voltage on the power-good pin thereby telling the motherboard it can boot/run/whatever (please excuse my layman's language)

whereas the other higher wattage supply is not putting out the voltage so there is a chance that it's not happy with itself!!!!!

I forgot to actually write down the voltages on the different pins to see if any of them are out of wack - shame though as i was hoping to use the higher rated supply as an emergency one till i got my rma sorted out.

thanks for your help Dai


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## jjbtnc (Aug 27, 2007)

ok

the 250 watt nps-250gb

=5v reads 5.15 ; 3.3.v reads 3.34v ; 12v reads 11.68 ;-12v reads -11.93v ; 5vsb reads 5.14 and power_ok reads 5.14v

all voltages in spec (but not under load!) as it has this voltage on the power_good pin it runs the motherboard!


on the 330w nps-300gb

5v reads 5.22v ; 3.3v reads 3.34v ; 12v reads 11.44v ; -12 reads 11.91 ; -5v reads -5.02 v ; 5vsb reads 5.11v
i believe they are all in spec of +or- 5% but the power_good is reading zero, well 0.02

I've read on some sites that some of the cheaper psus son't have a true power_good signal they just wire off from another 5v signal to this pin - so the psu doesn't check if it's performing well enough before attempting to run the motherboard it just runs the motherboard.
i could do the same manually and so in theory have this psu run the motherboard.

is it really asking for trouble though? as i said before the voltages seem to be in spec so in theory it shouldn't do any damage to the motherboard/components and should run the motherboard ok

Agree? disagree? LOL


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## dai (Jul 2, 2004)

both are dicey the second is that close to out of spec on the 12v line you may as well consider it out


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## TheMatt (May 9, 2006)

The Power_Good signal should be between 3v and 6v. Sorry I didn't read the entire thread.


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## jjbtnc (Aug 27, 2007)

Thanks guys - yeah it would be a bit risky and not worth it.
been up and running on the 250w max nps0250gb for a day now so hopefully it will be ok until the warranty replacement comes through.
what i did though was remove/unplug any components that aren't essential.
When the antec psu went i initially removed all components bar cpu, graphics card, 1 stick of ram (i disconnected the hard drives/dvd drives and even the front switches and leds) as all i was concerned with at first was whether the motherboard/cpu was still ok.

Checked the replacement psu and plugged it in to the motherboard and then shorted the power on pins on the motherboard to fire her up. Ran ok so i started to put things on 1 by 1, starting with the front switches and leds, then the hard drives, and then a dvd writer.

gonna leave it at that - i only need 1 dvd drive not 2, i don't need the pci cards for extra usb and firewire and dialup modem at the moment.
So just having 1 dvd writer and 2 hard drives plugged in will do me for now and keep the power demands as low as possible.

I do miss my pci audigy sound card though - according to the antec power usage checker adding the sound card brings me really close to 250w limit and that's on an old 250w max psu, so i don't know if it's worth trying the audigy or not. I do have onboard sound which is disabled at the moment, i wonder if that would be less power demanding, though i'd have to check that even with the audigy not plugged in,whether i have to uninstall the creative drivers before installing the onboard drivers.

I might even consider underclocking the cpu temporarily.

thanks again guys


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## TheMatt (May 9, 2006)

jjbtnc said:


> - is a Dell nps-300gb - 330w max - which is a 24pin atx psu and as with a lot of dells has a non standard pin out - i've been through and checked all the voltages on the pins and i'm quite happy with moding the wiring to make it a standard atx connector.


One thing to note with the Dell proprietary PSUs is that the 20-pin ATX connector doesn't just have the wires switched around, they are completely different. The Dell 20-pin connector included no 3.3v pins and a lot more 5v pins. You can't just move around the wires. You should probably end up getting a new PSU.

Hope this helps. Don't try using that Dell proprietary PSU.


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