Electrolytics blow after 1 hr
Jeff Liebermann
the local recycler and proceed to try and raise the dead. I've done
this many times with good success, but not this time. Upon initial
inspection, I find the usual bulging electrolytic caps. There were 4
identical caps, 2200uF 6.3VDC 105C. I replace them with 2200uF 10VDC
105C caps (Panasonic ECA-1AHG222). Note the increase in working
voltage. These are brand new caps from Digikey. I run the unit
overnight and find that two of the caps now have bulging tops.
Assuming that I may have had some marginal caps in the bag (unlikely
but worth testing), I replace the two that bulged with 2200uF 10v 85C
caps (Panasonic ECA-1AM222) also from Digikey. This is somewhat of a
downgrade, but should work. I also replace the power supply, for no
better reason than I had a spare.
Same problem as before. The two caps blew their tops within a few
hours, leaking caustic goo.
<http://802.11junk.com/jeffl/crud/GX520-bad-caps.jpg>
The two large black caps in the foreground are the surviving 105C
caps, while the blue caps in the background, are the bulging 85C caps.
Using my finger and a thermocouple thermometer, I determined that the
bulging caps are not getting warm or at least are not any warmer than
other nearby components.
I've replace literally hundreds of caps but I've never seen this
before. It really makes me wonder if the bad caps problem might be
caused by something other than defective caps and/or marginal
capacitor voltage ratings.
Duz anyone have a clue as to what is causing this problem? I haven't
had time to probe the board for power supply bus noise or excessive
current quite yet. What I could use is some speculation as to the
probable culprit.
--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831-336-2558
# http://802.11junk.com je...@cruzio.com
# http://www.LearnByDestroying.com AE6KS
William Sommerwerck
Jamie
caps with virtually no R in them.. Otherwise, they'll heat up in side
a bit and vent, or partially get there.
Jamie
who where
wrote:
>Another day in bad caps hell. I fish a Dell GX520 out of the pile at
>the local recycler and proceed to try and raise the dead. I've done
>this many times with good success, but not this time. Upon initial
>inspection, I find the usual bulging electrolytic caps. There were 4
>identical caps, 2200uF 6.3VDC 105C. I replace them with 2200uF 10VDC
>105C caps (Panasonic ECA-1AHG222). Note the increase in working
>voltage. These are brand new caps from Digikey. I run the unit
>overnight and find that two of the caps now have bulging tops.
(snip)
>Duz anyone have a clue as to what is causing this problem? I haven't
>had time to probe the board for power supply bus noise or excessive
>current quite yet. What I could use is some speculation as to the
>probable culprit.
Jeff, I've been reading your posts long enough to conclude you know
what you're doing, generally in spades.
But ... did you check the polarity? I ask that because there are
cases where the PCB screen legend was arse-about, causing grief to
cap-replacers who didn't record the "outgoing" cap polarity and match
that against the screening.
Otherwise, if heating isn't an issue then what WW said is a
possibility.
who where
>Otherwise, if heating isn't an issue then what WW said is a
>possibility.
Typo alert! Would you believe "what WS said"?
Phil Allison
"Jeff Liebermann"
> <http://802.11junk.com/jeffl/crud/GX520-bad-caps.jpg>
>
> The two large black caps in the foreground are the surviving 105C
> caps, while the blue caps in the background, are the bulging 85C caps.
** Errr - I hate to tell you this pal ........
but the pic shows all 4 caps installed with reverse polarity.
A smaller cap ( C310) is clearly installed correctly and so are all the
others I can see.
The markings on the PCB are a bit unusual with the white triangle indicating
positive.
.... Phil
Arfa Daily
"Phil Allison" <phi...@tpg.com.au> wrote in message
news:8sls4j...@mid.individual.net...
I think that triangle is actually a "+" sign, and if so, I agree
Arfa
Phil Allison
"Arfa Daily"
> "Phil Allison"
>
> "Jeff Liebermann"
>>
>>> <http://802.11junk.com/jeffl/crud/GX520-bad-caps.jpg>
>>>
>>> The two large black caps in the foreground are the surviving 105C
>>> caps, while the blue caps in the background, are the bulging 85C caps.
>>
>>
>> ** Errr - I hate to tell you this pal ........
>>
>> but the pic shows all 4 caps installed with reverse polarity.
>>
>> A smaller cap ( C310) is clearly installed correctly and so are all the
>> others I can see.
>>
>> The markings on the PCB are a bit unusual with the white triangle
>> indicating positive.
>
>
>
** I see a white circle outlining each electro, then a solid white
triangle making a chord across the same circle plus a large white "+" sign
right next to the triangle.
The bulging electros are in all in backwards .....
..... Phil
tm
"Jeff Liebermann" <je...@cruzio.com> wrote in message
news:0e9bm6h2ikhm2pfmd...@4ax.com...
The caps are in backwards.
tm
Jeff Liebermann
wrote:
AAAAAAARGH! I can't believe I did that. I usually assume that the
silk screened marker was matches the negative stripe on the
electrolytics. Very embarrassing.
Thanks for catching my mistake (as I crawl back into my hole and
sulk).
circuit
http://www.LearnByDestroying.com
"Jeff Liebermann" <je...@cruzio.com> wrote in message
news:rfkbm6hkov35ue2vb...@4ax.com...
circuit
practice through the decades, when a board is built, that all the polarities
of electrolytic caps face the same direction. Have seen a few cases the last
couple of years where this is NOT followed though.
William Sommerwerck
Frightening. I had the right idea ("AC getting through" is a subset of
"wrong polarity"), but I never would have guessed that. How can a
manufacturer so blatantly ignore a standard that's been around for
I-don't-know-how-many-decades?
Jeffrey Angus
That's easy, there's so many standards to choose from.
Jeff
William Sommerwerck
>> Frightening. I had the right idea ("AC getting through" is a subset
>> of "wrong polarity"), but I never would have guessed that. How can
>> a manufacturer so blatantly ignore a standard that's been around for
>> I-don't-know-how-many-decades?
> That's easy, there's so many standards to choose from.
Well, "many" standards is equivalent to "no" standard! <grin>
Years ago, when I was working in Ecuador at a NASA site, we had to replace
some blown power rectifiers. I -- and everyone else -- assumed that power
rectifiers always had the cathode on the bolt end. Uh-uh. These were
backwards -- anode-to-bolt -- so our replacements kept blowing.
Jim Yanik
> On Thu, 24 Feb 2011 12:44:58 +1100, "Phil Allison" <phi...@tpg.com.au>
> wrote:
>
>>"Jeff Liebermann"
>>
>>> <http://802.11junk.com/jeffl/crud/GX520-bad-caps.jpg>
>>>
>>> The two large black caps in the foreground are the surviving 105C
>>> caps, while the blue caps in the background, are the bulging 85C
>>> caps.
>
>>** Errr - I hate to tell you this pal ........
>>
>>but the pic shows all 4 caps installed with reverse polarity.
>>
>>A smaller cap ( C310) is clearly installed correctly and so are all
>>the others I can see.
>>
>>The markings on the PCB are a bit unusual with the white triangle
>>indicating positive.
>>
>>.... Phil
>
> AAAAAAARGH! I can't believe I did that. I usually assume that the
> silk screened marker was matches the negative stripe on the
> electrolytics. Very embarrassing.
>
> Thanks for catching my mistake (as I crawl back into my hole and
> sulk).
>
>
I reversed an electrolytic once,it blew and sprayed goo on the side of my
face,and foil in the instrument.
it's not as bad as my cutting through a power cord (missing GND pin,needed
replacement) that was still plugged in. :-(
Big flash and loud KAPOW,hole in diagonal pliers,and boss nearby was
filling out my performance review,and was working on the part about
following safety prodcedures. I'm glad the pliers had insulated handles.
--
Jim Yanik
jyanik
at
localnet
dot com
William Sommerwerck
> Big flash and loud KAPOW, hole in diagonal pliers...
You're lucky you didn't get molten metal in your eye. I once deliberately
shorted out an AC line with a scredriver. The result was not at all pretty.
N_Cook
news:ik5oho$q4c$1...@news.eternal-september.org...
An instructor told me, ass-u-me anything and you will make an ASS of U and
ME
Mike Tomlinson
<phi...@tpg.com.au> writes
>but the pic shows all 4 caps installed with reverse polarity.
Bingo.
--
Mike Tomlinson
Meat Plow
What makes a cap pop? Heat. Voltage/current surges. Figure it out.
--
Live Fast, Die Young and Leave a Pretty Corpse
Meat Plow
> On Thu, 24 Feb 2011 12:44:58 +1100, "Phil Allison" <phi...@tpg.com.au>
> wrote:
>
>>"Jeff Liebermann"
>>
>>> <http://802.11junk.com/jeffl/crud/GX520-bad-caps.jpg>
>>>
>>> The two large black caps in the foreground are the surviving 105C
>>> caps, while the blue caps in the background, are the bulging 85C caps.
>
>>** Errr - I hate to tell you this pal ........
>>
>>but the pic shows all 4 caps installed with reverse polarity.
>>
>>A smaller cap ( C310) is clearly installed correctly and so are all the
>>others I can see.
>>
>>The markings on the PCB are a bit unusual with the white triangle
>>indicating positive.
>>
>>.... Phil
>
> AAAAAAARGH! I can't believe I did that. I usually assume that the silk
> screened marker was matches the negative stripe on the electrolytics.
> Very embarrassing.
>
> Thanks for catching my mistake (as I crawl back into my hole and sulk).
Lol not the first time that's happened.
Jeff Liebermann
wrote:
>I reversed an electrolytic once,it blew and sprayed goo on the side of my
>face,and foil in the instrument.
Only once? I think I've probably done it maybe 10 or more times in my
life. Sometimes, nothing happens. Other times, I spray smoldering
oily confetti all over the shop. Back in the tube days, I once
managed to convert a metal can electrolytic into a small rocket, that
cracked the Bakelite(?) case on the TV. With tantalums, the amount of
toxic smog that such a small device can produce is truly impressive.
Of course, after discovering I had simultaneously missed the obvious
and ruined my reputation for infallibility, I managed to make things
worse. I had visitors in the office at the time, and was engaged in a
very distracting conversation, while trying to replace the reversed
electrolytics. Of course, I had solder in two caps backwards before I
noticed that I had repeated my mistake. It's really hard to ignore
the silk screened + sign, and the square pad on the + lead but I
succeeded. Since it was obvious that nothing useful or successful was
going to happen last night, I replaced the caps, ran a few simple
tests, and made a hasty exit towards home.
In the true spirit of Learn By Destroying(tm), I measured the
temperature of the various caps with a thermocouple probe. 36C on all
4 caps whether inserted backwards or correctly. Basically, the same
temperature as most everything else in the area. It appears that
these caps do NOT get unusually hot when reversed. Some do, but these
didn't. Also, I'm rather impressed that the Dell PCB pads did not
fall apart after having the same parts replaced ummm.... 4 times.
>it's not as bad as my cutting through a power cord (missing GND pin,needed
>replacement) that was still plugged in. :-(
>Big flash and loud KAPOW,hole in diagonal pliers,and boss nearby was
>filling out my performance review,and was working on the part about
>following safety prodcedures. I'm glad the pliers had insulated handles.
Nicely done. I vaguely recall cutting across a hot zip cord while
plugged in, and destroying a pair of borrowed pliers. That was minor
compared to all my other mistakes and accidents, which I'll mercifully
decline to itemize.
--
Jeff Liebermann je...@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
Jeffrey Angus
> Only once? I think I've probably done it maybe 10 or more times in my
> life. Sometimes, nothing happens. Other times, I spray smoldering
> oily confetti all over the shop.
One of my first "I did this" projects was a small line powered
phonograph amplifier built from the RCA Tube Manual book.
It's pretty impressive when you put the voltage doubler caps
in backwards.
Lesson learned, "Electrolytic capacitors are fussy about polarity."
Or course later on, this came in hand when we used to shove a
250 uF 150 V "little beaver" into the end of a line cord and
leave it in the trash can next to another tech's bench. Wait
until they're deep in the middle of something and plug the cord
in.
Great hilarity ensued.
Jeff
The other other one.
Baron
Good catch Phil :-)
--
Best Regards:
Baron.
Baron
> On Thu, 24 Feb 2011 12:44:58 +1100, "Phil Allison" <phi...@tpg.com.au>
> wrote:
>
>>"Jeff Liebermann"
>>
>>> <http://802.11junk.com/jeffl/crud/GX520-bad-caps.jpg>
>>>
>>> The two large black caps in the foreground are the surviving 105C
>>> caps, while the blue caps in the background, are the bulging 85C
>>> caps.
>
>>** Errr - I hate to tell you this pal ........
>>
>>but the pic shows all 4 caps installed with reverse polarity.
>>
>>A smaller cap ( C310) is clearly installed correctly and so are all
>>the others I can see.
>>
>>The markings on the PCB are a bit unusual with the white triangle
>>indicating positive.
>>
>>.... Phil
>
> AAAAAAARGH! I can't believe I did that. I usually assume that the
> silk screened marker was matches the negative stripe on the
> electrolytics. Very embarrassing.
>
> Thanks for catching my mistake (as I crawl back into my hole and
> sulk).
>
I wouldn't beat yourself up about it... I'll bet we have all made some
mistakes in our time. :-)
--
Best Regards:
Baron.
Meat Plow
I once was trying to remove a photographer's external slave flash
powerpack from it's case using two hemostats. I happened to clamp on the
plus and minus output. I think it was 900 volts dc and had several large
electrolytics about 3/4 the size of a soda can. Residual voltage caused
my arms to fly outward and I stabbed a friend in the shoulder with one
pair or the hemostats.
Arfa Daily
"Jeff Liebermann" <je...@cruzio.com> wrote in message
news:rfkbm6hkov35ue2vb...@4ax.com...
> On Thu, 24 Feb 2011 12:44:58 +1100, "Phil Allison" <phi...@tpg.com.au>
> wrote:
>
>>"Jeff Liebermann"
>>
>>> <http://802.11junk.com/jeffl/crud/GX520-bad-caps.jpg>
>>>
>>> The two large black caps in the foreground are the surviving 105C
>>> caps, while the blue caps in the background, are the bulging 85C caps.
>
>>** Errr - I hate to tell you this pal ........
>>
>>but the pic shows all 4 caps installed with reverse polarity.
>>
>>A smaller cap ( C310) is clearly installed correctly and so are all the
>>others I can see.
>>
>>The markings on the PCB are a bit unusual with the white triangle
>>indicating
>>positive.
>>
>>.... Phil
>
> AAAAAAARGH! I can't believe I did that. I usually assume that the
> silk screened marker was matches the negative stripe on the
> electrolytics. Very embarrassing.
>
> Thanks for catching my mistake (as I crawl back into my hole and
> sulk).
>
>
> --
> # Jeff Liebermann
Ah, but we've all been there Jeff, we've all been there ... :-)
Arfa
Mike Tomlinson
<je...@cruzio.com> writes
>Nicely done. I vaguely recall cutting across a hot zip cord while
>plugged in, and destroying a pair of borrowed pliers.
I did exactly that a few weeks ago in a moment of inattention.
Fortunately, because we have a decent electrical wiring code here in the
UK, all that happened was that the 3A fuse in the plug blew.
Over that side of the pond, the only protection you have is a 16A or 32A
breaker in the cabinet, which explains the destroyed pliers.
--
Mike Tomlinson
Smitty Two
Mike Tomlinson <mi...@jasper.org.uk> wrote:
> Over that side of the pond, the only protection you have is a 16A or 32A
> breaker in the cabinet
I wonder how many sides the pond has. The U.S. has no 16 or 32 amp
breakers.
Mike Tomlinson
september.org>, Smitty Two <prest...@earthlink.net> writes
>I wonder how many sides the pond has. The U.S. has no 16 or 32 amp
>breakers.
Whatever.
The point still applies. You only have the cabinet breaker to protect
the circuit, here we have individual fuses per plug in addition to
whatever fuse(s) the connected equipment has.
--
Mike Tomlinson
Jeff Liebermann
In the USA, we only make big mistakes, so oversized breakers are
totally functional. We also use it as a Darwinian filter, as sloppy
techs usually don't survive very long. After 150 years of natural
selection, we have bred a race of very careful technicians.
Circuit breakers here are in increments of 5A up to about 25A for
domestic service. None of my breakers are labeled, so if I need to
know which breaker controls which circuit, I just plug a short into
the wall socket, and check which breaker has tripped. Very handy.
Michael A. Terrell
All that proves is that you live in a 'nanny state'.
--
You can't fix stupid. You can't even put a band-aid on it, because it's
Teflon coated.
Baron
> I once was trying to remove a photographer's external slave flash
> powerpack from it's case using two hemostats. I happened to clamp on
> the plus and minus output. I think it was 900 volts dc and had several
> large electrolytics about 3/4 the size of a soda can. Residual voltage
> caused my arms to fly outward and I stabbed a friend in the shoulder
> with one pair or the hemostats.
>
>
Ouch !
--
Best Regards:
Baron.
Mike Tomlinson
Terrell <mike.t...@earthlink.net> writes
> All that proves is that you live in a 'nanny state'.
Actually, it proves that we have a well designed and well thought out
premises wiring code which protects people and the appliances they use.
And we can actually boil a kettle in a reasonable amount of time.
What are the figures for electrical fires in the USA again?
--
Mike Tomlinson
Jeff Liebermann
<mi...@jasper.org.uk> wrote:
>What are the figures for electrical fires in the USA again?
310 deaths last year. About 1/3 of the electrical fires involve
electrical shorts of some sort. Even with fuses in the power plugs,
shorts in the walls will have the same effect in both systems:
<http://www.interfire.org/features/electric_wiring_faults.asp>
...for 1993 - 1997 are that 41,200 home structure fires
per year are attributed to ‘electrical distribution.’ These
electrical distribution fires account for 336 civilian deaths,
1446 civilian injuries, and $643.9 million in direct property
damage per year.
<http://www.nfpa.org/assets/files//PDF/Proceedings/Ahrens_presentation.pdf>
<http://www.usfa.dhs.gov/citizens/home_fire_prev/electrical.shtm>
During a typical year, home electrical problems account for
28,600 fires and $1.1 billion in property losses. 53% of
residential electrical fires involve electrical wiring.
I couldn't find any statistics for UK.
Michael A. Terrell
Mike Tomlinson wrote:
>
> In article ?ipCdnVpbGqRrm_XQ...@earthlink.com?, Michael A.
> Terrell ?mike.t...@earthlink.net? writes
>
> ? All that proves is that you live in a 'nanny state'.
>
> Actually, it proves that we have a well designed and well thought out
> premises wiring code which protects people and the appliances they use.
> And we can actually boil a kettle in a reasonable amount of time.
>
> What are the figures for electrical fires in the USA again?
They are available online if you really care.
What are the figures for the UK?
--
You can't fix stupid. You can't even put a Band-Aid™ on it, because it's
Teflon coated.
John Robertson
> On Mon, 28 Feb 2011 11:19:25 +0000, Mike Tomlinson
> <mi...@jasper.org.uk> wrote:
>
>> What are the figures for electrical fires in the USA again?
>
> 310 deaths last year. About 1/3 of the electrical fires involve
> electrical shorts of some sort. Even with fuses in the power plugs,
> shorts in the walls will have the same effect in both systems:
> <http://www.interfire.org/features/electric_wiring_faults.asp>
> ...for 1993 - 1997 are that 41,200 home structure fires
> per year are attributed to ‘electrical distribution.’ These
> electrical distribution fires account for 336 civilian deaths,
> 1446 civilian injuries, and $643.9 million in direct property
> damage per year.
>
> <http://www.nfpa.org/assets/files//PDF/Proceedings/Ahrens_presentation.pdf>
>
> <http://www.usfa.dhs.gov/citizens/home_fire_prev/electrical.shtm>
> During a typical year, home electrical problems account for
> 28,600 fires and $1.1 billion in property losses. 53% of
> residential electrical fires involve electrical wiring.
>
> I couldn't find any statistics for UK.
>
20,000/year electrical fires, etc. in the UK according to:
http://www.communities.gov.uk/news/corporate/1824335
3,000/year in Ontario Canada (about thirteen million folks):
http://www.niagarafalls.ca/city_hall/departments/fire_services/prevention/electricalfirehazards.asp
John :-#)#
--
(Please post followups or tech enquiries to the newsgroup)
John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9
Call (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."
Mike Tomlinson
Terrell <mike.t...@earthlink.net> writes
> They are available online if you really care.
Evasion of question noted.
--
(\__/)
(='.'=)
(")_(")
Michael A. Terrell
Mike Tomlinson wrote:
>
> In article <IrSdnSmKNKGoYPbQ...@earthlink.com>, Michael A.
> Terrell <mike.t...@earthlink.net> writes
>
> > They are available online if you really care.
>
> Evasion of question noted.
Evasion? Numbers for both the US and UK were posted in this thread.
From what I saw, the UK is a huge tnderbox of poorly wired buildings.
Then, multiply the UK numbers by 5 to compare them to the US.