Power supply

Eberhard Roloff tuxebi at gmx.de
Wed Dec 3 11:50:57 UTC 2008

Steven Vollom wrote:

> I am down to the motherboard and the power supply.  If the power supply 
> is OK, ASUS recognizes the problem as theirs.  The Heat Sink Fan does 
> not run, when I boot up.  It did run, when I put it on one of the 3 pin 
> fan slots.  When connected properly, if the 4 pin connector doesn't work 
> the power to the processor may not work.  
When the 3pin connector worked and the fan was spinning, this is an 
indication that at least something from the PSU is working. It does not 
prove anything, but at least it is not totally dead. The same goes for 
the motherboad.
I would assume, that your fan on the sink does not power up, because the 
4pin connector is controlled by a circuit that only operates the fan, 
when needed.

It also probably supplies the
> 4 pin.  So if the cable from the power supply that goes to the Processor 
> is defective, that is the problem.  Otherwise it is the motherboard.  Is 
> there a way to check the power from the power supply that goes to the

Yes, there is.

GEnerally, in order to operate the power supply outside the computer 
(i.e. disconnected from it) you need to shorten 2 leads of the large 
power supply connector and also add a certain "load", like 2 harddisks, 
a few fans, a 12V bulp or similar. Otherwise it will not start, not 
because it's defective, just because there is no load.

So you better use it, when it's connected to the PC.

Have a multimeter ready and a VERY close look here, also looking at the 
links that are referenced there at the bottom of the page. 

There you can see, what voltage each connector should deliver. Mainly 
you should see 12V and 5V.

DISCLAIMER: You are on your own. I will not accept any liability for any 
damage to your hardware or your health that might occur.
 From my experience it is not very difficult to destroy a motherboard, 
CPU and/or a PSU.

If you are not confident that you can handle this, you might be better 
off, if you temporarily take the PSU from your current computer and use 
this for testing, whether your new PSU is faulty.

You might also very easily use your new PSU to power your old computer. 
Doing this you will easily see, whether it's largely defective or not.

In Addition:

Should you have any questions, I cordially invite you to mail me 
personally and off-list with any questions you might have, before you 
will do anything, being uncertain, how to do it.

kind regards and good luck

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