Can a bad mobo damage a good power supply?

I have a computer that is damaged due to a near-by lightning strike.

I tested the power supply with my little power supply tester, and it shows
no -5v leg, and a red 'danger' light comes on. So, I replace the power
supply with a new one, plug the puter back into the wall, hit the button,
and guess what? Nothing, that's what. I put the new power supply on my
little power supply tester and it shows the exact same thing as the 'known
bad' power supply showed, no -5v leg and a red 'danger' light comes on.

What gives?

I did not check the new power supply to make sure that it was good before
installing it, therefore there is a chance that the new power supply was bad
all along.

or,

is there anything in the mobo (or elsewhere) that would damage a good power
supply in this way?

I don't want to install yet another power supply if there is a chance that
it can be damaged, too.

Thanks, y'all.

--
Captain Lon

Captain Lon

On Wed, 06 Jul 2005 19:47:29 GMT, "Captain Lon" <>
wrote:

>I have a computer that is damaged due to a near-by lightning strike.
>
>I tested the power supply with my little power supply tester, and it shows
>no -5v leg, and a red 'danger' light comes on. So, I replace the power
>supply with a new one, plug the puter back into the wall, hit the button,
>and guess what? Nothing, that's what. I put the new power supply on my
>little power supply tester and it shows the exact same thing as the 'known
>bad' power supply showed, no -5v leg and a red 'danger' light comes on.
>
>What gives?
>
>I did not check the new power supply to make sure that it was good before
>installing it, therefore there is a chance that the new power supply was bad
>all along.
>
>or,
>
>is there anything in the mobo (or elsewhere) that would damage a good power
>supply in this way?
>
>I don't want to install yet another power supply if there is a chance that
>it can be damaged, too.
>
>Thanks, y'all.

Did you check the supply under load? Switching power supplies need
about 10% of rated load on the +5 at least, and possibly other legs as
well.

Yes, a bad motherboard can damage a power supply.

Tom

Tom MacIntyre

Tom wrote: > Did you check the supply under load?

How would I do that in this situation? I did not have a working computer,
so I am puzzled as to how to go about this.

--
Captain Lon

A good sailor does not need good luck or a boat!


"Tom MacIntyre" <> wrote in message
news:...
> On Wed, 06 Jul 2005 19:47:29 GMT, "Captain Lon" <>
> wrote:
>
>>I have a computer that is damaged due to a near-by lightning strike.
>>
>>I tested the power supply with my little power supply tester, and it shows
>>no -5v leg, and a red 'danger' light comes on. So, I replace the power
>>supply with a new one, plug the puter back into the wall, hit the button,
>>and guess what? Nothing, that's what. I put the new power supply on my
>>little power supply tester and it shows the exact same thing as the 'known
>>bad' power supply showed, no -5v leg and a red 'danger' light comes on.
>>
>>What gives?
>>
>>I did not check the new power supply to make sure that it was good before
>>installing it, therefore there is a chance that the new power supply was
>>bad
>>all along.
>>
>>or,
>>
>>is there anything in the mobo (or elsewhere) that would damage a good
>>power
>>supply in this way?
>>
>>I don't want to install yet another power supply if there is a chance that
>>it can be damaged, too.
>>
>>Thanks, y'all.
>
> Did you check the supply under load? Switching power supplies need
> about 10% of rated load on the +5 at least, and possibly other legs as
> well.
>
> Yes, a bad motherboard can damage a power supply.
>
> Tom

Captain Lon

On Wed, 06 Jul 2005 20:33:52 GMT, "Captain Lon" <>
wrote:

>Tom wrote: > Did you check the supply under load?
>
>How would I do that in this situation? I did not have a working computer,
>so I am puzzled as to how to go about this.

A different motherboard with the same or similar PS requirements.
Sometimes you can get away with using automotive bulbs or the
appropriate resistor values, but they'd have to be calculated based on
the PS, and they'd probably get a little hot also.

Tom

Tom MacIntyre

Hey Tom. A good power supply tester is the load. Mine is designed to be
plugged into the MB plug and gives a load so that the supply comes on. It's
not a good idea to leave it on for long. The instructions on the tester say
not to and it does get pretty warm but it gives me a green light if all of
the voltages are right.

AG
"Tom MacIntyre" <> wrote in message
news:...
> On Wed, 06 Jul 2005 19:47:29 GMT, "Captain Lon" <>
> wrote:
>
>>I have a computer that is damaged due to a near-by lightning strike.
>>
>>I tested the power supply with my little power supply tester, and it shows
>>no -5v leg, and a red 'danger' light comes on. So, I replace the power
>>supply with a new one, plug the puter back into the wall, hit the button,
>>and guess what? Nothing, that's what. I put the new power supply on my
>>little power supply tester and it shows the exact same thing as the 'known
>>bad' power supply showed, no -5v leg and a red 'danger' light comes on.
>>
>>What gives?
>>
>>I did not check the new power supply to make sure that it was good before
>>installing it, therefore there is a chance that the new power supply was
>>bad
>>all along.
>>
>>or,
>>
>>is there anything in the mobo (or elsewhere) that would damage a good
>>power
>>supply in this way?
>>
>>I don't want to install yet another power supply if there is a chance that
>>it can be damaged, too.
>>
>>Thanks, y'all.
>
> Did you check the supply under load? Switching power supplies need
> about 10% of rated load on the +5 at least, and possibly other legs as
> well.
>
> Yes, a bad motherboard can damage a power supply.
>
> Tom

AG

First, a power supply can test just fine on those testers
and still fail in the computer. The best load is a computer.
The best tester is a 3.5 digit multimeter that also provides
essential numbers. Numbers that report more about that power
supply's health AND other parts of the power supply system.
The power supply system is not just a power supply.
Summarizes of how to check a power supply were posted
previously in:
"Computer doesnt start at all" in alt.comp.hardware on 10
Jan 2004 at
http://tinyurl.com/2t69q and
"I think my power supply is dead" in alt.comp.hardware on 5
Feb 2004 at
http://tinyurl.com/yvbw9 .

In your case, most important first numbers are from purple
wire before powering computer and from purple, gray, and green
wire after power button is pressed.

Second, can motherboard damage a power supply? No, as
others have stated. Correctly posted was a reply even 30
years ago. Short together all power supply outputs, and still
the supply must not be damaged by that short circuit. Power
supplies even 30 years ago protected themselves from load
damage.

Function (that the power supply manufacturer should have
provided in writing) is called overpower protection. However
power supply manufacturers that are missing essential and
required functions also forget to provide written specs.
Claim nothing and one cannot be held liable for the defective
product. Therefore inferior supplies forget to provide
written specifications.

There is no faster way to confirm the integrity of, or
locate the defective component in your power supply 'system'.
Get a meter and have important numbers in but two minutes.
Even if those numbers mean nothing to you, to others those
numbers provide far more information than yet posted. Without
those numbers, currently, your responses are mostly
speculation.

Captain Lon wrote:
> Tom wrote: > Did you check the supply under load?
>
> How would I do that in this situation? I did not have a working
> computer, so I am puzzled as to how to go about this.

w_tom