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'[EE] Bulging capacitors'
2007\10\27@145715 by Tony Smith

picon face
Remember them?  Bloated and leaking all over your circuit boards?

I had a PVR starting to act flaky, claiming the hard drive was full.  Hmmm,
drive must be failing.  Pull the drive, put it in a PC to copy the files,
and find it works perfectly well.

Replace drive in PVR, and it won't boot.  Drive goes 'click click click...'.
Check voltages, everything ok.  Uh oh.  Back to the PC, and the drive is
still ok.  Ok, it's a power problem.  Maybe, as the PVR works fine without
the drive.

But then power supply looks ok...  Apart from that capacitor with the dome.
Nah, that 'stolen formula dodgy cap' stuff went out of fashion in 2001,
didn't it?  This box is from early 2005 (well, the chips are).

Replace capacitor and everything is fine.  The old one may have been low
ESR, just how do you tell anyway?

Anyone else noticed this still happening?

No wonder the old radio guys hate caps.  Another time was when a VCR got
unplugged for the first time in years and wouldn't restart.  Flatmate said
to toss it and get a new one (so much for her hippy cred).  I found a
capacitor on the power-up delay had dried out.  A new one got it working,
the old one became the "Hippies For Rampant Consumerism' Award.

Tony

2007\10\27@154802 by Randy Glenn

picon face
I think around 2005 Nichicon had a problem with caps with too much
electrolyte in them. Could that have been it?

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

-Randy

On 10/27/07, Tony Smith <spam_OUTajsmithTakeThisOuTspamrivernet.com.au> wrote:
{Quote hidden}

> -

2007\10\27@171258 by Jinx

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> Anyone else noticed this still happening?

I spent most of Wednesday deep in the guts of a 1986 Akai amp
trying to find out why volume had gone way down on one side. A
minute signal-path 1uF had bulged on the underside and gone very
high R. Extremely satisfying to find that and get the volume up after
6 months of the balance pot being at 99:1. Not quite so enjoyable
(but prudent I guess) re-soldering a zillion 20-year old joints and
over-soldering the hundreds of brittle wire-wrap inter-connections

But to answer your question........no ;-)

2007\10\27@171449 by Herbert Graf

flavicon
face

On Sun, 2007-10-28 at 05:56 +1100, Tony Smith wrote:
> Remember them?  Bloated and leaking all over your circuit boards?
>
> I had a PVR starting to act flaky, claiming the hard drive was full.  Hmmm,
> drive must be failing.  Pull the drive, put it in a PC to copy the files,
> and find it works perfectly well.
>
> Replace drive in PVR, and it won't boot.  Drive goes 'click click click...'.
> Check voltages, everything ok.  Uh oh.  Back to the PC, and the drive is
> still ok.  Ok, it's a power problem.  Maybe, as the PVR works fine without
> the drive.
>
> But then power supply looks ok...  Apart from that capacitor with the dome.
> Nah, that 'stolen formula dodgy cap' stuff went out of fashion in 2001,
> didn't it?  This box is from early 2005 (well, the chips are).
>
> Replace capacitor and everything is fine.  The old one may have been low
> ESR, just how do you tell anyway?
>
> Anyone else noticed this still happening?

Yes. It's always been happening, the "stolen formula" period just had an
amazingly large rash of these issues.

I once repaired a TV of mine with that problem, was at least 15 years
old. Two bulging caps replaced in the power supply circuitry (they were
200V+ caps) and the TV still works to this day.

TTYL

2007\10\27@173310 by Neil Cherry

picon face
Jinx wrote:
>> Anyone else noticed this still happening?
>
> I spent most of Wednesday deep in the guts of a 1986 Akai amp
> trying to find out why volume had gone way down on one side. A
> minute signal-path 1uF had bulged on the underside and gone very
> high R. Extremely satisfying to find that and get the volume up after
> 6 months of the balance pot being at 99:1. Not quite so enjoyable
> (but prudent I guess) re-soldering a zillion 20-year old joints and
> over-soldering the hundreds of brittle wire-wrap inter-connections
>
> But to answer your question........no ;-)

We've lost a lot of little 3Com switch/router thingies (I don't
support these devices directly) and a number of _old_ fancy switches
made by a company who I think I'd better not name (I want to keep
my job). The problem in all of them is bulging/pop'd caps. Our routers
and big Frame & ATM switches are not having this problem.

--
Linux Home Automation         Neil Cherry       .....ncherryKILLspamspam@spam@linuxha.com
http://www.linuxha.com/                         Main site
http://linuxha.blogspot.com/                    My HA Blog
Author of:            Linux Smart Homes For Dummies

2007\10\27@175042 by Jinx

face picon face
> may have been low ESR, just how do you tell anyway?

ESR meter ?

> No wonder the old radio guys hate caps

I notice that restorers routinely replace old (paper, wax, electro) caps.
When possible they mount the replacement inside the body of the old
one to keep up appearances. When that's not possible, the old one is
left inside the radio, taped to the case, to show the original parts used

2007\10\27@190500 by Mike Harrison

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face

>No wonder the old radio guys hate caps.  Another time was when a VCR got
>unplugged for the first time in years and wouldn't restart.  Flatmate said
>to toss it and get a new one (so much for her hippy cred).  I found a
>capacitor on the power-up delay had dried out.  A new one got it working,
>the old one became the "Hippies For Rampant Consumerism' Award.

This is a very common failure mode for things like VCRs which spend most of their life powered on,
and run fairly warm - the cap on the startup supply goes leaky, but not so leaky that it loads the
supply when running - the fault only manifests itself after a powerdown, when the startup supply
can't get high enough through the high-value resistor that supplies it during startup.

Presented with a SMPS that fails to start, the first thing I do is look for a low-voltage
electrolytic in the mains side and replace it. at least half the time this fixes it.


2007\10\27@203227 by Jinx

face picon face

> This is a very common failure mode for things like VCRs which
> spend most of their life powered on, and run fairly warm - the
> cap on the startup supply goes leaky

One that does deteriorate over time is the back-up clock supercap.
Although they're claimed to start at 0.47F or 1F and can power the
time for up to an hour, after a few years that time drops dramatically.
Supercaps I've pulled from most VCRs are not much good at all

2007\10\27@222416 by David VanHorn

picon face
A long time ago, I worked for Muzak.  After repairing amps there for a
few months, I noticed that the root cause of most of our field
failures were bad electrolytics. The guys had been replacing the bad
transistors and whatever caps were noticably bad, and putting them
back in service.
When I started pre-emptively replacing electrolytics on any failure,
(not just the ones that were already bad, but anything that was old or
had a lot of current) our re-repair rate fell off to near zero.

2007\10\28@085906 by Tony Smith

picon face
>
> I think around 2005 Nichicon had a problem with caps with too
> much electrolyte in them. Could that have been it?
>
> http://en.wikipedia.org/wiki/Capacitor_plague


Maybe.  It's just been a while since I've come across one, I fixed quite a
few PC motherboards a few years back, and replaced a few power supplies that
went bang.

Caps that dry out is different, that's been happening forever.

Oh well, something else to look forward too.

Tony

2007\10\28@085930 by Tony Smith

picon face
> > may have been low ESR, just how do you tell anyway?
>
> ESR meter ?


I suppose, but wouldn't it read high anyway?  The ones that go bang would be
really high.  A bit moot as I don't have an ESR meter.

I was interesting that there was no ripple on the output.  This was the 12v
rail, obviously it couldn't supply the power for the drive to start
spinning.

Tony

2007\10\28@181914 by Russell McMahon

face
flavicon
face
>> I think around 2005 Nichicon had a problem with caps with
>> too
>> much electrolyte in them. Could that have been it?
>>
>> http://en.wikipedia.org/wiki/Capacitor_plague

[added by me]

___________

My friend Ken Mardle says (also citing the above article):

There is a well-known problem with 1000uF/6V3 electrolytic
capacitors dying
on nVidia GeForce FX5200 video adaptor cards in Dell 8300
PC's.  The caps
are in some kind of local switchmode voltage regulator.
There are four
identical caps on the board and typically two of them bulge
(and in some
cases leak electrolyte) and develop very high leakage (100's
of mA @ 5V in
my case).  The card stops working or displays random stripes
and other junk.

I've had to replace the caps in two of our machines (and
many others on the
web report the same problem).

[It is reported that]There was also a problem with
bulging/exploding caps on motherboards in Dell
Optiplex GX270 machines.  [It is reported that] Dell even
set aside a big lump of money in
expectation of having to deal with the problem.  The
original CNET article
is here: [folded link]

"www.news.com/PCs-plagued-by-bad-capacitors/2100-1041_3-5942647.html?t
ag=nefd.lede
"

There is a general article here:

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

Regards,

Ken Mardle

___________________

           Russell

2007\10\28@181915 by Russell McMahon

face
flavicon
face
> I suppose, but wouldn't it read high anyway?  The ones
> that go bang would be
> really high.  A bit moot as I don't have an ESR meter.

Easy ESR tester.

Square wave source at V around 1 Volt.
Lower the impedance the better.
(Having a stiff enough source to not be loaded too much by
ESR + resistor load helps brain when calculating.)
Series resistor to test point - value maybe a bit above
expected ESR levels.
Oscilloscope at test point.

Observe waveform at each end of resistor (or across resistor
and at one end or whatever works for you).

When square waveform steps it will initially be constrained
only by the ESR/resistor ratio.
Ignore what happens from then on until next transition as it
will be affected by capacitor value.
Apply Ohms law.

IF source drops under load apply intelligent processing of
readings.

Vstep/Vsignal = ESR/(ESR+Series_R)
or for Vstep/Vsignal = k

   ESR = kR/(1-k)


eg Assuming stiff 1 volt square wave.
Series 4R resistor (nice simple arithmetic)
If cap voltage steps by 0.2 Volts at transition then

k = 0.2/1 = 0.2
ESR =  kR/(1-k) = 0.2 x 4 / (1-0.2) = 1 ohm.

E&OE.

This can be very useful in testing a large number of similar
items or for a specific situation as a relative change on
ESR will be easily noticed.



       Russell


2007\10\28@201759 by Howard Winter

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flavicon
picon face
Tony,

On Sun, 28 Oct 2007 23:58:24 +1100, Tony Smith wrote:

> > > may have been low ESR, just how do you tell anyway?
> >
> > ESR meter ?
>
>
> I suppose, but wouldn't it read high anyway?  The ones that go bang would be
> really high.  A bit moot as I don't have an ESR meter.

Err - hang on, I think you have this backwards.  The problem is high ESR - you want it to be low, especially in a Power Supply.

Cheers,


Howard Winter
St.Albans, England


2007\10\29@095218 by M. Adam Davis

face picon face
Even nice electrolytics have lifetimes measured only in the thousands
of hours at reasonable temperatures.  The typical power supply is much
warmer, and the lifetime is cut considerably.  Some badly designed
products leave the entire power supply turned on even when the machine
is off, rather than have another more efficient standby power supply.

That's why a lot of robust designs avoid electrolytic altogether, at a
higher price and with design changes, of course.

-Adam

On 10/27/07, Tony Smith <ajsmithspamKILLspamrivernet.com.au> wrote:
{Quote hidden}

> -

2007\10\29@105127 by David VanHorn

picon face
On 10/29/07, M. Adam Davis <.....stienmanKILLspamspam.....gmail.com> wrote:
> Even nice electrolytics have lifetimes measured only in the thousands
> of hours at reasonable temperatures.  The typical power supply is much
> warmer, and the lifetime is cut considerably.  Some badly designed
> products leave the entire power supply turned on even when the machine
> is off, rather than have another more efficient standby power supply.


One thing I discovered at Muzak, was that failure rates of equipment
that was turned on and off a lot was MUCH higher than the same
equipment left on all the time.

Later, I put this knowlege into a power cycler to shake out weak
components in repaired credit card terminals. It used an SSR to turn
on for a random amount of time, as short as 1/2 cycle, and as long as
30 seconds, and pretty much everything inbetween.  The repair guys
hated it, because many repaired terminals didn't make it through
cycling, but once we shook out the weak parts, the terminals that got
delivered had very low failure rates.  Normally, those were left on
all the time, or turned off once a day when the business closed.

The 2000 hour (or whavever the number) doubles for every 10C below
rated temperature, and also has ripple current and frequency
determinants.  Jim Williams had a really good formula for predicting
cap lifetime, but I've lost track of which book it's in.

2007\10\29@111913 by Jeff Findley

flavicon
face

"Russell McMahon" <EraseMEapptechspam_OUTspamTakeThisOuTparadise.net.nz> wrote in message
news:014501c819b0$9be1bca0$e701a8c0@y2k...
> My friend Ken Mardle says (also citing the above article):
>
> There is a well-known problem with 1000uF/6V3 electrolytic
> capacitors dying
> on nVidia GeForce FX5200 video adaptor cards in Dell 8300
> PC's.  The caps
> are in some kind of local switchmode voltage regulator.
> There are four
> identical caps on the board and typically two of them bulge
> (and in some
> cases leak electrolyte) and develop very high leakage (100's
> of mA @ 5V in
> my case).  The card stops working or displays random stripes
> and other junk.

I had the same sort of problem with ECS K7S-5A motherboards.  Three of us at
work bought this motherboard and they all eventually died.  I fixed mine by
replacing pretty much all the big caps I could with new ones.  The ones I
didn't replace with new ones, I replaced with ones that looked good that I
pulled from another (dead) motherboard.

Jeff
--
   "When transportation is cheap, frequent, reliable, and flexible,
everything else becomes easier."
- Jon Goff



2007\10\30@072550 by Tony Smith

picon face

> > > may have been low ESR, just how do you tell anyway?
> > >
> > > ESR meter ?
> >
> >
> > I suppose, but wouldn't it read high anyway? The ones that go bang
> > would be really high. A bit moot as I don't have an ESR meter.
>
> Err - hang on, I think you have this backwards. The problem is high
> ESR - you want it to be low, especially in a Power Supply.


I'm not confused, although I appear so when on TV.

I assumed it's a low ESR type (or was as some point), I was just wondering
how you find out the specs on a random cap without actually testing it.  In
this case, testing isn't much use...

Low uF seemed to be more of the problem than high ESR.  It was a 1000uF 16v
cap, which I replaced with a 470 one that was lying about.  It powered up
the drive just fine with that, so I added a second one and put it back
together.  Reliability yet to be determined.  :)

I haven't bothered testing its uF value (I know it's under 470uF!), I might
buy the 'proper' one and try out Russells test for some comparisons.

Tony

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