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

Started by jjbtnc, Aug 27, 2007, 19:54

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hello - my old psu just failed on me.

I have 2 possible emergency replacements until i get a permanent replacement.

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)

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

Mohie Ali

Hi there

You are doing the hard way,

Simple as this :

1- get a new power supply

2- In Most ATX connectors, the connector has two pieces one is 20 pin and the other is 4 pin and easly you can split them

3- So, if you have an old Dell system with 20 pin connector, then you can use 20 pin part only.

4- From what I know all ATX motherboard have to use standard ATX connector 

I hope this help


Hi - thanks for your reply, and yes it was helpful

i sort of know what you mean about the 'hard way' and quite agree with your info - the only thing is that my psu is still under warranty with antec so a replacement from them is being sorted.
This post has come from the fact i want to try to muddle through until the replacement comes through

thanks for your advice!