[Tfug] Pizza-box power problem

[erich]

OK
      I got it pulled apart. Have extracted the riser card. Nothing 
looks burned/bulged.
That's right. Failed electrolytic capacitors mean voltage ripple. CMOS 
components
do not like ripple. I don't think we have that problem in this case: 
Once the motherboard
is properly energized it works fine.
      I know this is a long shot but I'm taking the part to SWS to see 
if it can be replaced.

      The box has a QA inspection stamp dated Jun 5 2001 :)

                                                                                                                                           
Erich
Bexley Hall wrote:
> Hi Zack,
>
> On 12/14/2012 1:08 PM, Zack Williams wrote:
>> On Fri, Dec 14, 2012 at 11:37 AM, Bexley Hall<bexley401 at yahoo.com>  
>> wrote:
>>>
>>> I've also encountered "the" bad cap *inside* the power supply
>>> itself!  So, the MB can look (and *be*!) good -- the problem
>>> lying in the supply, instead.
>>
>> +1.  I've seen them in both.
>
> The PS is easy to overlook -- when you think the symptoms match
> problems you see on the MB!  First time I encountered a bad cap
> in a PS had me stumped -- symptoms *looked* like a bad cap but
> all the caps "appeared nominal", were from reputable manufacturers,
> etc.  "What am I failing to *see*??  Ah, power supply is also
> part of this chain..."
>
>> Especially hard to deal with when the PSU is somewhat unique.
>
> Yeah, I've got a cute little "4 CD" enclosure with a blown PS.
> Oddball size, shape, etc.  So, I'll have to service it.  But,
> hasn't percolated to the top of my ToDo list, yet...
>
>>> Ideally, you'd want a voltmeter to look at the actual voltages
>>> coming from the supply (though I suspect these will be nominal)
>>> and a 'scope to see the sorts of ripple you're encountering
>>> (which is a sign of how well/poorly the caps are performing
>>> their duties).
>>
>> Best do to this when the machine is connected/running, as the voltages
>> can be wonky when tested in isolation.
>
> Ideally, under a dynamic load.
>
> And, be sure not to slip with the scope probe (and remember the
> collar around the probe is ground so it doesn't want to bump
> into anything, either!)
>
> I toasted a large audio amplifier when I was in school by
> "slipping" with the scope probe.  <frown>  At those voltages
> and power levels, you don't just get magic *smoke*, you also
> get magic *flame*!!  :-/
>
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