[Tfug] power supplies & motherboards

[Harry McGregor]

erich wrote:
> OK,
>        Thanks. The person I had the conversation with was a non-technical
> hear-say person.
>         My first attempt to resuscitate  this box  ended in failure
> because
> it was later determined that the "new" power supply was bad. My friend
> has assured me that another "new" power supply  will be tested first
> before it enters my shop. If this 2nd attempt fails then I will end up
> with an uninstalled power supply and a motherboard that is e-waste.
>         It is difficult to test a power supply stand-alone. The new ones
> have many sensing feedback controls that work only in the
> appropriate environment.

That is not true...  You just have to short the correct pins in the ATX
connector, and it will fire up.

You can then test voltages all you want.

The pin is between the mess of black (ground) wires in the connector,
and is PS_ON or Power ON

http://en.wikipedia.org/wiki/ATX#Power_supply

I used to use this trick to power a bunch of hard drives for wiping with
DBAN.

You can also get a handy dandy power supply tester rather cheap.  I
think SWS has them in town, or you can order one:

http://www.geeks.com/details.asp?invtid=KM-LCD-1&cpc=SCH

http://www.newegg.com/Product/Product.aspx?Item=N82E16899887102&cm_re=power_supply_tester-_-99-887-102-_-Product

Also, some older motherboards (mostly with ISA slots) need a -5 volt
rail, and a lot of newer power supplies don't have the -5V rail.

                      Harry


>                                                                                           
> Erich
> Harry McGregor wrote:
>> Hi,
>>
>> erich wrote:
>>  
>>> OK,
>>>        I have a vintage 2004 tower that had a power supply failure.
>>> At least I'm pretty sure it was the power supply: the smell
>>> of burnt components came from the power supply. The
>>> motherboard smells/shows no signs of damage.
>>>
>>>        Then I heard a rather disturbing thing in a conversation.
>>> Power supplies have been known to fail on some models
>>> of computers and take out the motherboard with them.
>>>
>>>         So I have two questions:
>>>
>>>            1) If a power supply fails, is there a chance that
>>> it will take out a motherboard?
>>>     
>>
>> This can of course happen, depending on the failure in the power
>> supply.  I have seen far far more power supply failures that did NOT
>> kill the motherboard, but I have seen a couple that did...
>>
>>  
>>>            2) If a motherboard is suspected to have failed.
>>> will it take out a power supply?
>>>
>>>     
>> Unlikely, power supplies have short protection built in, about the worst
>> you could do is try to draw more power than the PS can provide, but that
>> would most likely be noticeable ahead of time.
>>
>> I would suggest getting a cheap power supply (I know, in general, not a
>> great idea), and if it works with that, get a good power supply, and
>> keep the cheap one as a bench supply for testing.
>>
>>
>>                    Harry
>>
>>
>>  
>>>                                                                   Erich
>>>
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>
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