[Tfug] Pizza-box power problem

[Bexley Hall]

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*!!  :-/