[ale] Pictures of the culprit (was OT: Diagnosing HW problem)

[Calvin Harrigan]

Jeff Hubbs wrote:

>I think that's either a regulator IC or a power transistor.
>
>Jeff
>
>On Tue, 2005-06-14 at 22:16 -0400, James P. Kinney III wrote:
>  
>
>>WooHoo! Nice pics of dead hardware!
>>
>>That stuff is power component devices. Likely a capacitor used to trim the
>>power to the CPU (they are often the largest things on the board).
>>
>>If I recall, you had some power supply issues with this rig earlier. It is
>>likely that the PS was failing and cracked/nearly blew the case open on
>>the cap. The new PS is fine but the on-rush of current was the end of the
>>part.
>>
>>The _bad_ news is you are likely not going to get a new mobo on a warranty
>>return. Unless the board was super expensive it's not worth a claim to
>>insurance.
>>
>>As to tv tuner cable being the source of the power spike, Yes! It CAN happen.
>>
>>My first system that I bought myself was toasted during a lightning strike
>>that was too close to the phone line. The box was OFF and UNPLUGGED but
>>the phone line to the modem was still in and the modem was serial port
>>cabled to the box. Chips were exploded in the modem, the mother board had
>>burn marks all over it between traces and the hard drive heads were welded
>>to the drive.
>>
>>More recently, lightning hit a tree outside my office (~5' from where I
>>was standing!!). The EMP wave trashed all sorts of things. It induced a
>>high voltage on wires like the Cat5e all over the office. That destroyed
>>NICs and routers and switches and (I'm convinced but lacking direct
>>evidence) the untimely dead of motherboard and hard drive 2 days later.
>>I'll never forget seeing a pair of flourescent light tubes that were still
>>in the plastic wrap leaning against the wall lit up like they were running
>>at 500W instead of 35W! That was what let me figure out that the EMP
>>induced an electric field over 5kV! All of my surge protectors were
>>unphased. Even the first line of one shot wall wart protectors.
>>
>>So a very nearby lightning show even with great surge protection can wreak
>>havoc.
>>
>>    
>>
>>>Guys,
>>>
>>>After examining the mb with a flashlight, I found the culprit.
>>>
>>>See:
>>>
>>>http://www.sourceillustrated.com/mb_1.jpg
>>>http://www.sourceillustrated.com/mb_2.jpg
>>>
>>>Ok...now for real technical lingo here...
>>>
>>>Of the four square thingies with the silver circle in the middle, notice
>>>one is most definitely *not* like the other.  First, what is this fried
>>>and charred thingie?  Second, does this look like it may have resulted
>>>from a lightning strike (we had some good ones here this weekend).  I have
>>>the box behind a good surge protector and UPS, but like a DAU I have cable
>>>running directly into a tv tuner card with no surge protection, so I'm
>>>wondering if that may have provided a clear path.
>>>
>>>Interested in learning your thoughts.  Thanks again for the help!
>>>
>>>John
>>>
>>>_______________________________________________
>>>Ale mailing list
>>>Ale at ale.org
>>>http://www.ale.org/mailman/listinfo/ale
>>>
>>>      
>>>
>>_______________________________________________
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>>Ale at ale.org
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>>    
>>
>
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>  
>
Seems like a power transistor (probably a MOSFET)  for the switch mode 
regulator. Typically used to drop the 3.3 Volts down to the 1.4-2.0 
volts used by most CPUs.  That circuit is pretty far in from the outside 
world.  If I had to take a guess two things might have happened, it was 
shorted by a screw or some other piece of metal or the least likely one 
of the capacitors shorted and caused an over current situation.  Either 
way motherboard is bye-bye.  Sorry.

Calvin...