Stupid question

  • Thread starter klem kedidelhopper
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klem kedidelhopper

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Lately I've had more than a few flat screens in the shop with bulged
capacitors in the power supply. I've noticed that in many of these
sets there might be for instance two or three 1000UF caps in parallel.
Is there any reason in the manufacturing process to parallel three
1000UF capacitors when one 3300UF would do the job? Lenny
 
On Wed, 1 Jun 2011 11:47:18 -0700 (PDT), klem kedidelhopper
<captainvideo462009@gmail.com> wrote:

Lately I've had more than a few flat screens in the shop with bulged
capacitors in the power supply.
Click to expand...
Shhhh... replacing such parts is what's keeping me in business.

I've noticed that in many of these
sets there might be for instance two or three 1000UF caps in parallel.
Is there any reason in the manufacturing process to parallel three
1000UF capacitors when one 3300UF would do the job? Lenny
Click to expand...
Height. Flat panel LCD monitors tend to be rather thin. Everyone
wants low profile thin products these daze. 3300uF caps tend to be
taller than 1000uF caps. I don't know exactly why, but it seems to do
with the way the foil and insulators are wrapped inside the can. I
haven't seen any short and fat PCB mount caps. While it's possible to
use axial leaded caps instead of radial, the robotic insertion
hardware greatly prefers radial leads.
--
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
 
klem kedidelhopper wrote:

Lately I've had more than a few flat screens in the shop with bulged
capacitors in the power supply. I've noticed that in many of these
sets there might be for instance two or three 1000UF caps in parallel.
Is there any reason in the manufacturing process to parallel three
1000UF capacitors when one 3300UF would do the job? Lenny
You get better ESR results with smaller cap values.
Click to expand...

Jamie
 
"Jamie" <jamie_ka1lpa_not_valid_after_ka1lpa_@charter.net> wrote in message
news:e1wFp.19195$pi2.17799@newsfe11.iad...
klem kedidelhopper wrote:

Lately I've had more than a few flat screens in the shop with bulged
capacitors in the power supply. I've noticed that in many of these
sets there might be for instance two or three 1000UF caps in parallel.
Is there any reason in the manufacturing process to parallel three
1000UF capacitors when one 3300UF would do the job? Lenny
You get better ESR results with smaller cap values.
Click to expand...
More to the point, the difference in ESR is not directly proportional to the
different sizes of capacitor, so 3x 1000uF has ESR of not much more than 1/3
that of a single 3000uF.
 
"Ian Field" wrote in message news:OqxFp.28874$A05.2940@newsfe13.ams2...


"Jamie" <jamie_ka1lpa_not_valid_after_ka1lpa_@charter.net> wrote in message
news:e1wFp.19195$pi2.17799@newsfe11.iad...
klem kedidelhopper wrote:

Lately I've had more than a few flat screens in the shop with bulged
capacitors in the power supply. I've noticed that in many of these
sets there might be for instance two or three 1000UF caps in parallel.
Is there any reason in the manufacturing process to parallel three
1000UF capacitors when one 3300UF would do the job? Lenny
You get better ESR results with smaller cap values.
Click to expand...
More to the point, the difference in ESR is not directly proportional to the
different sizes of capacitor, so 3x 1000uF has ESR of not much more than 1/3
that of a single 3000uF.

It's the form factor, as Jeff has suggested.
 
On Wed, 1 Jun 2011 17:59:44 -0400, "Charles"
<charlesschuler@comcast.net> wrote:

More to the point, the difference in ESR is not directly proportional to the
different sizes of capacitor, so 3x 1000uF has ESR of not much more than 1/3
that of a single 3000uF.
Click to expand...
Easy enough to test, or so I thought. First, I spend 10 minutes
rescuing my Dick Smith ESR meter from the Gordian Knot of tangled
cables behind my test equipment wall. I then find an old PCB (Okidata
320 printer board) with 3300uf 35v and 1000uf 35v Rubyeon
electrolytics. Carefully measuring the ESR, I get;
1000 uF 35v = 0.05 ohms
3300 uf 35v = 0.04 ohms
So much for the 3x theory. I'll see if I can find some 6.3v or 10v
caps, which should (hopefully) give higher ESR readings that are not
at the extreme of the meter range.

It's the form factor, as Jeff has suggested.
Click to expand...
Well, maybe not. The 3300 uf is only about 1mm taller than the 1000
uF cap, and a little less than twice as wide.
<http://802.11junk.com/jeffl/crud/ESR-test-01.jpg>
I would have thought the 3300 uF would be somewhat larger.

I just hate it when my measurements don't agree with my guesswork.

--
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
 
"klem kedidelhopper"


** This six toed, retarded freakoid has no other kind of question.
 
On Jun 2, 1:20 am, Jeff Liebermann <je...@cruzio.com> wrote:
On Wed, 1 Jun 2011 17:59:44 -0400, "Charles"

charlesschu...@comcast.net> wrote:
More to the point, the difference in ESR is not directly proportional to the
different sizes of capacitor, so 3x 1000uF has ESR of not much more than 1/3
that of a single 3000uF.

Easy enough to test, or so I thought.  First, I spend 10 minutes
rescuing my Dick Smith ESR meter from the Gordian Knot of tangled
cables behind my test equipment wall.  I then find an old PCB (Okidata
320 printer board) with 3300uf 35v and 1000uf 35v Rubyeon
electrolytics.  Carefully measuring the ESR, I get;
    1000 uF 35v = 0.05 ohms
    3300 uf 35v = 0.04 ohms
So much for the 3x theory.  I'll see if I can find some 6.3v or 10v
caps, which should (hopefully) give higher ESR readings that are not
at the extreme of the meter range.

It's the form factor, as Jeff has suggested.

Well, maybe not.  The 3300 uf is only about 1mm taller than the 1000
uF cap, and a little less than twice as wide.
http://802.11junk.com/jeffl/crud/ESR-test-01.jpg
I would have thought the 3300 uF would be somewhat larger.

I just hate it when my measurements don't agree with my guesswork.

--
Jeff Liebermann     je...@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558
Click to expand...
I wonder if your guess work and measurements may be correct Jeff. Your
test subjects were are old capacitors in a scrap board. Their
conditions may be questionable. Wouldn't you have to establish a "base
line" with new parts? And then even given that couldn't the variations
between new parts still come into question? Lenny
 
On Thu, 2 Jun 2011 07:11:29 -0700 (PDT), klem kedidelhopper
<captainvideo462009@gmail.com> wrote:

I wonder if your guess work and measurements may be correct Jeff. Your
test subjects were are old capacitors in a scrap board. Their
conditions may be questionable. Wouldn't you have to establish a "base
line" with new parts? And then even given that couldn't the variations
between new parts still come into question? Lenny
Click to expand...
True. I should use new parts. However, having two caps, with the
correct value, from the same manufacturer, was easier than trying to
find a new cap in my collection. I have plenty of 1000uF caps, but no
3300uF. Also, I forgot to test what 3ea 1000uF caps in parallel will
read.

However, that's not the problem. When the ESR values get below about
0.10 ohms, the readings are not very stable, heavily influenced by the
test leads, and what I consider not very reliable. They're good
enough for detecting a defective capacitor, but not really useful for
obtaining a definitive reading.

I'll try to drop into the local electronics stores in the next few
daze with my tester.

--
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" <jeffl@cruzio.com> wrote in message
news:s6gfu611ph4la4jae3a2ocre57un0ddik3@4ax.com...
On Thu, 2 Jun 2011 07:11:29 -0700 (PDT), klem kedidelhopper
captainvideo462009@gmail.com> wrote:

I wonder if your guess work and measurements may be correct Jeff. Your
test subjects were are old capacitors in a scrap board. Their
conditions may be questionable. Wouldn't you have to establish a "base
line" with new parts? And then even given that couldn't the variations
between new parts still come into question? Lenny

True. I should use new parts. However, having two caps, with the
correct value, from the same manufacturer, was easier than trying to
find a new cap in my collection. I have plenty of 1000uF caps, but no
3300uF. Also, I forgot to test what 3ea 1000uF caps in parallel will
read.

However, that's not the problem. When the ESR values get below about
0.10 ohms, the readings are not very stable, heavily influenced by the
test leads, and what I consider not very reliable. They're good
enough for detecting a defective capacitor, but not really useful for
obtaining a definitive reading.
Click to expand...

The proof of the pie is in the eating.

Try the 2 alternative arrangements in a practical SMPSU and scope the
ripple.
 
"Jeff Liebermann" wrote in message
news:s6gfu611ph4la4jae3a2ocre57un0ddik3@4ax.com...

On Thu, 2 Jun 2011 07:11:29 -0700 (PDT), klem kedidelhopper
<captainvideo462009@gmail.com> wrote:

I wonder if your guess work and measurements may be correct
Jeff. Your
test subjects were are old capacitors in a scrap board. Their
conditions may be questionable. Wouldn't you have to establish a
"base
line" with new parts? And then even given that couldn't the
variations
between new parts still come into question? Lenny
Click to expand...
True. I should use new parts. However, having two caps, with
the
correct value, from the same manufacturer, was easier than trying
to
find a new cap in my collection. I have plenty of 1000uF caps,
but no
3300uF. Also, I forgot to test what 3ea 1000uF caps in parallel
will
read.

However, that's not the problem. When the ESR values get below
about
0.10 ohms, the readings are not very stable, heavily influenced
by the
test leads, and what I consider not very reliable. They're good
enough for detecting a defective capacitor, but not really useful
for
obtaining a definitive reading.

I'll try to drop into the local electronics stores in the next
few
daze with my tester.

--
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, I looked at the data sheet for Panasonic FM series
capacitors:

1000 uF 16V - 19 mOhm at 100KHz
3300 uF 16V - 12 mOhm at 100KHz.
David
 
"David"

Jeff, I looked at the data sheet for Panasonic FM series capacitors:

1000 uF 16V - 19 mOhm at 100KHz
3300 uF 16V - 12 mOhm at 100KHz.
Click to expand...

** The penny finally drops.....

Now, imagine that the ripple current is divided three ways in the case of
using 3 caps and the reason for doing it is obvious.


..... Phil
 
On Jun 2, 7:43 pm, "Phil Allison" <phi...@tpg.com.au> wrote:
"David"

Jeff, I looked at the data sheet for Panasonic FM series capacitors:

1000 uF 16V - 19 mOhm at 100KHz
3300 uF 16V - 12 mOhm at 100KHz.

** The penny finally drops.....

Now, imagine that the ripple current is divided three ways in the case of
using 3 caps and the reason for doing it is obvious.

....  Phil
Click to expand...
I hadn't thought of that Phil but it makes sense. Lenny
 
On Thu, 2 Jun 2011 15:26:31 -0500, "David" <someone@somewhere.com>
wrote:

Jeff, I looked at the data sheet for Panasonic FM series
capacitors:

1000 uF 16V - 19 mOhm at 100KHz
3300 uF 16V - 12 mOhm at 100KHz.
David
Click to expand...
Thanks. That's the answer. 3 caps are better than one for ESR.
<http://www.panasonic.com/industrial/components/pdf/ABA0000CE108.pdf>
See column for "Impedance 100KHz".

I just noticed the "Endurance" column, which I guess means lifetime.
Values run from 2000 to 7000 hrs or 83 to 291 days. That would
suggest that if I leave my machines on 24 hrs/day at 105C, the caps
would blow up in 3-12 months. Good to know.

Back to measurements. I couldn't find a 3300uF cap, but did manage to
find some brand new 1000uF 10V and 2200uF 10V NHG caps.
uF ohms
1x 1000 0.16
2x 1000 0.09
3x 1000 0.04

1x 2200 0.10
2x 2200 0.05

Difficult to be certain because +/- one LSB will ruin any definitive
conclusion, but it seems like 2 caps are better than one big one. Two
1000uF caps in parallel yielded 0.09 ohms, while a single 2200uF cap
yielded 0.10. Still, it's difficult to proclaim a winner with only a
0.01 ohm difference.

--
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"
I just noticed the "Endurance" column, which I guess means lifetime.
Values run from 2000 to 7000 hrs or 83 to 291 days. That would
suggest that if I leave my machines on 24 hrs/day at 105C, the caps
would blow up in 3-12 months.
Click to expand...

** No - it means that with the caps operating at 105C ( due to both ambient
temp and ripple current ) - the rated life to when the ESR goes out of
spec is 83 to 291 days.

Derating tables show that the expected life extends to many years at more
typical equipment temps.


..... Phil
 
"klem kedidelhopper" <captainvideo462009@gmail.com> wrote in message
news:1febd9d5-d7b7-4022-a8f3-cdafd2a72680@m40g2000vbt.googlegroups.com...
On Jun 2, 7:43 pm, "Phil Allison" <phi...@tpg.com.au> wrote:
"David"

Jeff, I looked at the data sheet for Panasonic FM series capacitors:

1000 uF 16V - 19 mOhm at 100KHz
3300 uF 16V - 12 mOhm at 100KHz.

** The penny finally drops.....

Now, imagine that the ripple current is divided three ways in the case of
using 3 caps and the reason for doing it is obvious.

.... Phil
Click to expand...
I hadn't thought of that Phil but it makes sense. Lenny

##########################

There's also the increased surface area of 3 smaller caps that can dissipate
more heat and prolong life by running them that little bit cooler.
 
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