Backwards electrolytics (again)

J

Jeff Liebermann

Guest
It's another day in capacitor hell. About 2 months ago, I replaced
the bulging caps in a Dell Optiplex GX-520, but inserted them
backwards.
<http://802.11junk.com/jeffl/crud/GX520-bad-caps.jpg>
Today, I have an irate customer with a Dell XPS-200 that I sold him.
Same problem, again:
<http://802.11junk.com/jeffl/crud/xps200-bad-caps.jpg>
I had replaced 11 caps on this board, all of them backwards. It's
difficult to see on the photo, but the white silkscreened arrow is "+"
instead of the usual "-" . Now, I get to check all the other Dell
machines, where I probably inserted the caps backwards.
<http://802.11junk.com/jeffl/crud/For-Sale-PC.jpg>
Maybe I should find something else to do for a while? Grumble...



--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831-336-2558
# http://802.11junk.com jeffl@cruzio.com
# http://www.LearnByDestroying.com AE6KS
 
"Jeff Liebermann" <jeffl@cruzio.com> wrote in message
news:utg7p6dkggh8mvhr8mub58svj828s83vk5@4ax.com...
It's another day in capacitor hell. About 2 months ago, I replaced
the bulging caps in a Dell Optiplex GX-520, but inserted them
backwards.
http://802.11junk.com/jeffl/crud/GX520-bad-caps.jpg
Today, I have an irate customer with a Dell XPS-200 that I sold him.
Same problem, again:
http://802.11junk.com/jeffl/crud/xps200-bad-caps.jpg
I had replaced 11 caps on this board, all of them backwards. It's
difficult to see on the photo, but the white silkscreened arrow is "+"
instead of the usual "-" . Now, I get to check all the other Dell
machines, where I probably inserted the caps backwards.
http://802.11junk.com/jeffl/crud/For-Sale-PC.jpg
Maybe I should find something else to do for a while? Grumble...



--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831-336-2558
# http://802.11junk.com jeffl@cruzio.com
# http://www.LearnByDestroying.com AE6KS
Click to expand...
You IDIOT!!!
 
Good grief man, take some digital pix before you take it apart - at
least until you get over your brain fades.

G˛
 
"Jeff Liebermann"
It's another day in capacitor hell. About 2 months ago, I replaced
the bulging caps in a Dell Optiplex GX-520, but inserted them
backwards.
http://802.11junk.com/jeffl/crud/GX520-bad-caps.jpg
Today, I have an irate customer with a Dell XPS-200 that I sold him.
Same problem, again:
http://802.11junk.com/jeffl/crud/xps200-bad-caps.jpg
I had replaced 11 caps on this board, all of them backwards. It's
difficult to see on the photo, but the white silkscreened arrow is "+"
instead of the usual "-" . Now, I get to check all the other Dell
machines, where I probably inserted the caps backwards.
http://802.11junk.com/jeffl/crud/For-Sale-PC.jpg
Maybe I should find something else to do for a while? Grumble...
Click to expand...

** With all those damn electros installed in reverse polarity, be a damn
site easier to alter the DC rails to suit - wouldn't it ??



...... Phil ;-)
 
On Thu, 31 Mar 2011 21:36:31 +1100 "Phil Allison" <phil_a@tpg.com.au>
wrote in Message id: <8vj3pjF175U1@mid.individual.net>:

"Jeff Liebermann"

It's another day in capacitor hell. About 2 months ago, I replaced
the bulging caps in a Dell Optiplex GX-520, but inserted them
backwards.
http://802.11junk.com/jeffl/crud/GX520-bad-caps.jpg
Today, I have an irate customer with a Dell XPS-200 that I sold him.
Same problem, again:
http://802.11junk.com/jeffl/crud/xps200-bad-caps.jpg
I had replaced 11 caps on this board, all of them backwards. It's
difficult to see on the photo, but the white silkscreened arrow is "+"
instead of the usual "-" . Now, I get to check all the other Dell
machines, where I probably inserted the caps backwards.
http://802.11junk.com/jeffl/crud/For-Sale-PC.jpg
Maybe I should find something else to do for a while? Grumble...


** With all those damn electros installed in reverse polarity, be a damn
site easier to alter the DC rails to suit - wouldn't it ??
Click to expand...
Yeah! And take a video for us to see what happens when you power it up.
Extra points for audio. Make sure you use a 600W or better supply,
fold-overs just won't cut it. ;)
 
"Stroonz"

How did I do?


** Just as psycho, brainless and retarded as ever.
 
On Mar 31, 6:36 am, "Phil Allison" <phi...@tpg.com.au> wrote:
..
 ** With all those damn electros installed in reverse polarity, be a damn
site easier to alter the DC rails to suit  -  wouldn't it ??

.....  Phil   ;-)
Click to expand...

Geez Phil, what kind of Phil Allison answer is that? And a smiley
emoticon? Since you're off your game, I thought I'd take the liberty
and reply to Jeff in the proper Allison manner:

"Jeff LIeberfool"

It's another day in capacitor hell. About 2 months ago, I replaced
the bulging caps in a Dell Optiplex GX-520, but inserted them
backwards.
Click to expand...
** Are you f**king blind?

http://802.11junk.com/jeffl/crud/GX520-bad-caps.jpg
Today, I have an irate customer with a Dell XPS-200 that I sold him.
Same problem, again:
http://802.11junk.com/jeffl/crud/xps200-bad-caps.jpg
I had replaced 11 caps on this board, all of them backwards.
Click to expand...
** Twice? What kind of moron are you?


difficult to see on the photo, but the white silkscreened arrow is "+"
instead of the usual "-" . Now, I get to check all the other Dell
machines, where I probably inserted the caps backwards.
http://802.11junk.com/jeffl/crud/For-Sale-PC.jpg
Maybe I should find something else to do for a while? Grumble...
Click to expand...
** Yeah, like retire you idiot!

....Phil

How did I do?

Edwin
 
On Thu, 31 Mar 2011 21:36:31 +1100, "Phil Allison" <phil_a@tpg.com.au>
wrote:

** With all those damn electros installed in reverse polarity, be a damn
site easier to alter the DC rails to suit - wouldn't it ??
Click to expand...
I thought you would be amused. I don't think that the IC's would
appreciate the reversed power supply polarity.

It took me about 45 minutes to tear down the XPS-200, replace 11 caps,
reassemble, and test. It's now running an overnight burnin. I also
fixed two of the other machines in about 30 minutes each (fewer caps
to replace). What I found interesting was that the XPS-200 again
worked for about a week with reverse polarized caps. My usual 24
burnin is probably inadequate as I didn't bother doing a visual or
thermal inspection after the burnin.

Yes, I also learn from my mistakes.

--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
 
On Wed, 30 Mar 2011 21:00:22 -0700 (PDT), stratus46@yahoo.com wrote:

Good grief man, take some digital pix before you take it apart - at
least until you get over your brain fades.
Click to expand...
Welcome to Learn By Destroying(tm).

I take photos of every customers machine I work on. I blow off the
dust outside (so that it doesn't trash the office), take a few photos,
and then proceed to work on the machine. This has ended a few debates
over missing accessories, mechanical damage, etc. Sometimes, I use
one of the particularly disgusting photos as wallpaper on the repaired
machine. I also take some more photos when I'm done.

However, these were my machines, not customers, so I didn't bother
with the photos. Most were rescued from the recyclers and all of them
had bulging caps. Since these were mine, not customers, all my
customary precautions were ignored. Out of about 7 machines, I
managed to reverse the caps on 4 of them. All had the silk screened
stripe marking the "+" end instead of the usual "-" end. I didn't see
the "+" silk screened marking or bother checking the square pad, until
Phil Allison pointed it out in the first photo. The brain isn't
fading, but the eyesight is certainly going down the drain.
Assumption, the mother of all screwups, is also fully functional.


--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
 
Jeff Liebermann wrote:
On Thu, 31 Mar 2011 21:36:31 +1100, "Phil Allison" <phil_a@tpg.com.au
wrote:

** With all those damn electros installed in reverse polarity, be a damn
site easier to alter the DC rails to suit - wouldn't it ??

I thought you would be amused. I don't think that the IC's would
appreciate the reversed power supply polarity.

It took me about 45 minutes to tear down the XPS-200, replace 11 caps,
reassemble, and test. It's now running an overnight burnin. I also
fixed two of the other machines in about 30 minutes each (fewer caps
to replace). What I found interesting was that the XPS-200 again
worked for about a week with reverse polarized caps. My usual 24
burnin is probably inadequate as I didn't bother doing a visual or
thermal inspection after the burnin.

Yes, I also learn from my mistakes.
Click to expand...
An infra-red camera might be of use...or wet-touch each cap after its
been running a while (without exploding).

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."
 
Jeff Liebermann wrote:
Out of about 7 machines, I
managed to reverse the caps on 4 of them. All had the silk screened
stripe marking the "+" end instead of the usual "-" end. I didn't see
the "+" silk screened marking or bother checking the square pad, until
Phil Allison pointed it out in the first photo.
Click to expand...
BTW, not all Dell mobos are marked that way.

Do you mean you don't write a red dot next to the positive lead when
you remove each capacitor? :) I do that because I've come across
circuit boards that were marked wrong.
 
On Thu, 31 Mar 2011 10:27:03 -0700 (PDT), "larry moe 'n curly"
<larrymoencurly@my-deja.com> wrote:

Jeff Liebermann wrote:

Out of about 7 machines, I
managed to reverse the caps on 4 of them. All had the silk screened
stripe marking the "+" end instead of the usual "-" end. I didn't see
the "+" silk screened marking or bother checking the square pad, until
Phil Allison pointed it out in the first photo.

BTW, not all Dell mobos are marked that way.
Click to expand...
Yep. This is the first time I've seen boards marked that way and I've
been dealing with PC's since the Apple ][.

Do you mean you don't write a red dot next to the positive lead when
you remove each capacitor? :) I do that because I've come across
circuit boards that were marked wrong.
Click to expand...
I usually take a photograph. For major repairs, such as laptops, I
also print the photo, and mark any parts I replace. However, I
haven't found it necessary to mark the capacitor polarity. I have run
into some that were marked backwards, but that was maybe 10 years ago.
More commonly, capacitors where the silk screened markings are UNDER
the capacitor, where they can't be seen. When I do mark something on
the board, I use a UV pen for the top, and whatever I have handy for
the bottom (which can't be seen).

Worst case are some video cards, where the annular ring around the
solder bad is so narrow, that any attempt to solder the pad will
result in a guaranteed solder bridge. These also tend to have no
visible polarity markings of any kind, which adds to the challenge.

The problem here was that these machines were mine, not my customers.
So, I simply ignored all of this, and blundered onward with no photos
or markings.
--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831-336-2558
# http://802.11junk.com jeffl@cruzio.com
# http://www.LearnByDestroying.com AE6KS
 
On Thu, 31 Mar 2011 09:24:40 -0700, John Robertson <spam@flippers.com>
wrote:

An infra-red camera might be of use...or wet-touch each cap after its
been running a while (without exploding).
Click to expand...
I use a cheap IR thermometer with a bit of creative optics to narrow
the viewing angle, or a thermocouple thermometer. I need my finger
tips functional for playing piano, organ, synth, etc. What I found
odd on the GX-520 board with the backwards capacitors, was that they
did NOT become warm:
<http://groups.google.com/group/sci.electronics.repair/msg/feb66e8acd3d46a4>
I measured the temperature and the capacitors were the same
temperature as the surroundings. I would have expected them to get
warm, but apparently not. My guess(tm) is that the plastic insulator,
between the foil wraps and the aluminum case, is also a fair thermal
insulator. While the electrolyte is getting hot and boiling off
belching gasses, there is little heat transfer to the case.

If you haven't broken it and then fixed it, you don't understand it.

--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831-336-2558
# http://802.11junk.com jeffl@cruzio.com
# http://www.LearnByDestroying.com AE6KS
 
"Jeff Liebermann"
I measured the temperature and the capacitors were the same
temperature as the surroundings.
Click to expand...
** As is usually the case when the reverse voltage is only 3.3 or 5 volts.

I would have expected them to get warm, but apparently not.
Click to expand...
** Not IME at such low voltages.

My guess(tm) is that the plastic insulator,
between the foil wraps and the aluminum case, is also a fair thermal
insulator. While the electrolyte is getting hot and boiling off
belching gasses, there is little heat transfer to the case.
Click to expand...
** No way - boiling electrolyte would make the whole cap too hot to touch.
Electro caps are almost like living things - when faced with reverse
polarity, they try to re-form as reversed caps. There is a limit, of course
and much heat will be generated if the voltage is more than a few volts.

Anecdote:

The most alarming example of a reversed electro I ever came across was
inside a *new in carton* 300 watt per channel power amplifier made by Jands
Electronics here in Sydney (a model J600).

One of the two 8000uF, 80V filter chassis mount electros had been installed
in reverse in the factory but the darn thing actually worked for a few
minutes until the AC fuse blew. Some clear liquid was split round the
bottom of the case. On correcting the error - the thing worked OK. Of
course, it got a new cap from me.

Although the amp was new, it had apparently not been used in 8 or 9 years
since manufacture. So I rang Jands and gave them the serial number.
According to their records the particular amp had " gone missing" from the
factory and was never sold to any customer. An "inside job " was suspected.

My customer professed total innocence.....


...... Phil
 
Jeff Liebermann <jeffl@cruzio.com> wrote in
news:mfs9p6pgv82s5edol45usqnlojh1d8nbca@4ax.com:

On Thu, 31 Mar 2011 09:24:40 -0700, John Robertson <spam@flippers.com
wrote:

An infra-red camera might be of use...or wet-touch each cap after its
been running a while (without exploding).

I use a cheap IR thermometer with a bit of creative optics to narrow
the viewing angle, or a thermocouple thermometer. I need my finger
tips functional for playing piano, organ, synth, etc. What I found
odd on the GX-520 board with the backwards capacitors, was that they
did NOT become warm:
http://groups.google.com/group/sci.electronics.repair/msg/feb66e8acd3d4
6a4
I measured the temperature and the capacitors were the same
temperature as the surroundings. I would have expected them to get
warm, but apparently not. My guess(tm) is that the plastic insulator,
between the foil wraps and the aluminum case, is also a fair thermal
insulator. While the electrolyte is getting hot and boiling off
belching gasses, there is little heat transfer to the case.

If you haven't broken it and then fixed it, you don't understand it.
Click to expand...
They now make "fairly low cost" handheld IR scopes for firefighting use;
I saw one demonstrated on the local TV news,and it was sensitive enough to
see a 3-sec handprint on a wall. It could easily show up hot components on
a PCB.It was the size of a handheld portable spotlight. It might be
worthwhile reaserching,particularly if one has a small production business.

--
Jim Yanik
jyanik
at
localnet
dot com
 
On Fri, 1 Apr 2011 09:23:51 +1100, "Phil Allison" <phil_a@tpg.com.au>
wrote:

"Jeff Liebermann"

My guess(tm) is that the plastic insulator,
between the foil wraps and the aluminum case, is also a fair thermal
insulator. While the electrolyte is getting hot and boiling off
belching gasses, there is little heat transfer to the case.

** No way - boiling electrolyte would make the whole cap too hot to touch.
Electro caps are almost like living things - when faced with reverse
polarity, they try to re-form as reversed caps. There is a limit, of course
and much heat will be generated if the voltage is more than a few volts.
Click to expand...
Ok. I was assuming that the gas necessary to blow the lid off the
capacitor and spew brown goo was accompanied by heating. That seems
to be a bad assumption as the gases can probably be produced without
any heat. Time for a reverse polarity bench test with the proper
instrumentation. (Probably this weekend).

--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831-336-2558
# http://802.11junk.com jeffl@cruzio.com
# http://www.LearnByDestroying.com AE6KS
 
On Thu, 31 Mar 2011 19:14:31 -0500, Jim Yanik <jyanik@abuse.gov>
wrote:

They now make "fairly low cost" handheld IR scopes for firefighting use;
I saw one demonstrated on the local TV news,and it was sensitive enough to
see a 3-sec handprint on a wall. It could easily show up hot components on
a PCB.It was the size of a handheld portable spotlight. It might be
worthwhile reaserching,particularly if one has a small production business.
Click to expand...
FLIR makes these:
<http://www.flir.com>
Their lowest cost model is about $1000. Office next door does home
energy assessments and has one of these.
<http://www.flir.com/thermography/americas/us/content/?id=24072>
However, they won't let me borrow it any more after it got trashed by
someone else. While I had it, it was wonderful for finding shorted
power supply traces, overheating components, and CPU cooling problems.
I don't see myself spending $1000 for one in the near future.

However, I have built several IR flying spot scanners, that might
suffice. Basically just a far infrared photo detector chip, a
rotating mirror ripped out of a laser printer or supermarket scanner,
and some optics. I've built several of these over the years, with
assorted problems. All of them worked, but the response time was
awful compared to the various FLIR arrays. Thermal noise was also
bad.
<http://groups.google.com/group/sci.electronics.equipment/browse_thread/thread/92c3879a53a8f9f1>

The problem was that the caps really did not get warm. Per comments
by Phil Allison, little heat is not required to produce the gasses
that a bulging the case. I don't think the FLIR camera will show
anything useful.



--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831-336-2558
# http://802.11junk.com jeffl@cruzio.com
# http://www.LearnByDestroying.com AE6KS
 
On 31/03/2011 10:19 PM, Stroonz wrote:
On Mar 31, 6:36 am, "Phil Allison"<phi...@tpg.com.au> wrote:
.

** With all those damn electros installed in reverse polarity, be a damn
site easier to alter the DC rails to suit - wouldn't it ??

..... Phil ;-)


Geez Phil, what kind of Phil Allison answer is that? And a smiley
emoticon? Since you're off your game, I thought I'd take the liberty
and reply to Jeff in the proper Allison manner:
Click to expand...
Thing is, Jeff hasn't disagreed with Phil, or said something that Phil
disagrees with. Phil reserves his insults for what he regards to be
their proper use - as a debating tool.

Sylvia.
 
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