[Coco] OT -- PC needs TWO Shut Downs

[Gene Heskett]

On Tuesday 04 April 2006 03:07, RJRTTY at aol.com wrote:
>In a message dated 4/4/06 2:38:26 A.M. Eastern Daylight Time,
>
>gene.heskett at verizon.net writes:
>>An enterpriseing individual could make  this 'capacitor wizard'
>> thingie and peddle it for a lot less than $175  too, its not really
>> that complex a circuit.  Hey Roy, are you  listening?  For those
>> interested, see
>
>Hey, I leave the easy  stuff for the amatuers.  :)  At work we
>usually detected bad power  caps by using the AC voltage
>setting on a good quality analog  meter.

Yeah, but those are now made out of darnednearunobtainium.
Not to mention copper oxide rectifiers use in many of those pretty well 
fade away by the 10khz mark in terms of rectification efficiency.

And modern digital stuff often doesn't bother to block the dc component 
when measuring AC, and frankly don't have the frequency response to 
respond to a 50khz switching circuit.  I've checked a few well known 
brands and found them down >10db in response by 250hz!

>Any detectable 
>reading meant that the cap was bad.   THis was a common
>problem with the old analog systems.  Before  everything
>went digital and was replaced by workstation terminals.
>It was  so common that when anything was serviced for
>any reason the caps where  tested and replaced too as standard
>procedure.

We've changed about 3 of those 3 lb coffee cans full of those little 
1/8" x 3/16" surface mounted electrolytics used in the dvc-pro 
broadcast tape recorders since they were new about 10 years ago.  At 
the cost of those, we've bought the 15 $3k to $8k machines several 
times over.  The failure rate was so high (>40% of about a thousand per 
machine per year) there was a rumor that the users were going to get 
together and start a class action suit.  But nothing ever came from it 
I guess.  Winning it would have bankrupted Panasonic without a doubt.
And boards get to looking like they've been to a barbeque after the same 
cap has been replaced for the 5th time using that tweezer style iron 
from gc, running on a powerstat to keep it down in the 550-650 degree 
area.  Otherwise it gets way the heck too hot.

Based on the performance and lifetimes of those capacitors, I would 
never consider going that route for a new design.

>Roy

-- 
Cheers, Gene
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Copyright 2006 by Maurice Eugene Heskett, all rights reserved.