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From: Joe on 13 Mar 2010 21:37
I bought a Philips DVP 642 DVD player in December 2005, and 2 months shy
of 2 years, it failed - having symptoms of a well-known problem with a
certain capacitor in the power supply.

Well before the problem occurred, I had come across a description of the
failure and how to fix it by replacing a particular capacitor on the power
supply board.

It turns out that the particular capacitor supposedly would likely be
leaking some electrolyte or be bulging - it was doing neither.

When I opened up the player and left it turned on for a few minutes, that
particular capacitor became very much hotter than any other capacitor, so
I replaced it, and the player is still working now, some two years later.

A couple of years ago, I bought a Digital Stream DTX9900 digital to analog
converter box for my old TV. Son of a ... it too failed at about the 22
month mark. I opened up the case, and there it was - a bulging capacitor
on the power supply board.

I replaced that capacitor a couple of weeks ago, and the converter has
since been working.

Anybody else noticed any coincidences like these? About the only
similarity in use between these two boxes is that they both are on
"stand-by" power 24-7. Other than that, I use the converter a lot more
than the DVD player.

--- Joe
From: Phil Allison on 13 Mar 2010 22:08

"Joe"

>I bought a Philips DVP 642 DVD player in December 2005, and 2 months shy
> of 2 years, it failed - having symptoms of a well-known problem with a
> certain capacitor in the power supply.
>
> Well before the problem occurred, I had come across a description of the
> failure and how to fix it by replacing a particular capacitor on the power
> supply board.
>
> It turns out that the particular capacitor supposedly would likely be
> leaking some electrolyte or be bulging - it was doing neither.
>
> When I opened up the player and left it turned on for a few minutes, that
> particular capacitor became very much hotter than any other capacitor, so
> I replaced it, and the player is still working now, some two years later.
>
> A couple of years ago, I bought a Digital Stream DTX9900 digital to analog
> converter box for my old TV. Son of a ... it too failed at about the 22
> month mark. I opened up the case, and there it was - a bulging capacitor
> on the power supply board.
>
> I replaced that capacitor a couple of weeks ago, and the converter has
> since been working.
>
> Anybody else noticed any coincidences like these? About the only
> similarity in use between these two boxes is that they both are on
> "stand-by" power 24-7. Other than that, I use the converter a lot more
> than the DVD player.


** You can expect a no-brand electro operating in an environment of 65
degrees C to fail after 16,000 hours.

The answer is to turn all such devices off at the power point.



..... Phil









From: Jeff Liebermann on 14 Mar 2010 01:07
On Sat, 13 Mar 2010 18:37:29 -0800, none(a)given.now (Joe) wrote:

>Anybody else noticed any coincidences like these? About the only
>similarity in use between these two boxes is that they both are on
>"stand-by" power 24-7.

Heat kills electrolytic capacitors. Electrolytic life calculators:
<http://www.illinoiscapacitor.com/tech-center/life-calculators.aspx>
<http://www.cde.com/calc/>
<http://www.niccomp.com/Products/General/Alumlyticlifeexpect.pdf>
<http://www.edn.com/article/CA6588368.html>
<http://powerelectronics.com/images/archive/ElectrolyticCap.pdf>

For every 10C increase in temperature, the lifetime is cut roughly in
half. If the box runs hot, the caps won't last very long, especially
if they're running at the bitter edge of their voltage rating, and
have a high ripple current (common in power supply filter caps).

Note that this is for a perfectly normal electrolytic capacitor and
not the defective bulging variety caused by counterfeit electrolyte.
When a normal cap fails, it doesn't bulge. However, it does loose
capacitance and ESR rather rapidly. End-o-life is considered a 20%
drop in capacitance.

--
Jeff Liebermann jeffl(a)cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
From: Phil Allison on 14 Mar 2010 04:19

"Jeff Liebermann"

>
> Note that this is for a perfectly normal electrolytic capacitor and
> not the defective bulging variety caused by counterfeit electrolyte.
> When a normal cap fails, it doesn't bulge. However, it does loose
> capacitance and ESR rather rapidly. End-o-life is considered a 20%
> drop in capacitance.


** Electros do not lose capacitance until the ESR value has risen
dramatically.

This is why service techs use ESR meters to find bad and failing electro
caps and not capacitance meters.

Eg;

http://members.ozemail.com.au/~bobpar/esrmeter.htm


...... Phil




From: Chris Bartram on 14 Mar 2010 04:26
On 14/03/2010 02:37, Joe wrote:

> Anybody else noticed any coincidences like these? About the only
> similarity in use between these two boxes is that they both are on
> "stand-by" power 24-7. Other than that, I use the converter a lot more
> than the DVD player.
>
> --- Joe

Electrolytic caps have always been a failure point on anything switched
on all the time: a few years ago replacing them in printers at fire
stations was a regular task for me and my colleagues. As they were used
for callouts, these printers were on 24x7x365.

This is of course made worse by capacitor plague these days:

http://en.wikipedia.org/wiki/Capacitor_plague

I'm just about to replace a dodgy cap in my washing machine's control
board: the machine has been showing odd behaviour for a while, and
there's a 680uf 10v that is visibly bulging. The mchine isn't on all the
time, but the power switch is a soft on-off, so some parts must be
powerud up whenever it is plugged in. I'd say it's about 3 years old.
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