LCD Desktop Monitor Fading to White, then Black

[Jeff Liebermann]

On Mon, 3 May 2010 08:09:58 -0700 (PDT), saber850 <saber850@yahoo.com>
wrote:

Is there a way I can gain confidence that the problem is w/ the
capacitors, before opening it up?

Drugs work well for improving confidence. I find that I perform my
most heroic feats of daring and self-endangerment when thoroughly
doped to just below the point of going comatose. This steadies the
hand, improves on my diagnostic abilities, and opens me to a variety
of unusual approaches. The only problem is that I have difficulties
remembering what changes I've made while under the influence and have
therefore resorted to using a camcorder or digital camera. This helps
answer the inevitable questions "What was I thinking"?

I'll refrain from recommending specific controlled substances and
prescription drugs as each technician responds differently. For
starters, anti-depressants and anti-anxiety drugs work well for
elevating one's self-confidence.
<http://www.alphacalm.com/anti-anxiety-drugs/>

However, if the chemical confidence builder solution is not for you, I
suggest you purchase an ESR tester (see previous rant), and test the
capacitors in the circuit. Yes, it works without removing the caps.
Also, look for bulges, leaks, brown goo, and oozing rubber plugs.

--
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

 

[saber850]

On May 3, 11:20 am, saber850 <saber...@yahoo.com> wrote:

On May 3, 4:01 am, "N_Cook" <dive...@tcp.co.uk> wrote:



Jeff Liebermann <je...@cruzio.com> wrote in message

news:9edst5drns9dhhvmbonl5gds2v615pn9bm@4ax.com...

On Sun, 2 May 2010 17:53:14 -0700 (PDT), saber850 <saber...@yahoo.com
wrote:

On May 2, 5:10 pm, Jeff Liebermann <je...@cruzio.com> wrote:

This might be of interest:
http://pavel.kirkovsky.com/2009/03/samsung-syncmaster-204b-repair/
http://www.djhome.net/tips/samsungsyncmaster204T.htm
I've seen both problems on the bench with similar Samsung models.

This is great info; thanks.  The website links you found refer to the
problem as "flickering".  Is that the condition my monitor has, given
the video I posted?

No, it's not the same.  What's probably happening is that as your
power supply warms up, the cazapitors are starting to also get hot. My
guess(tm) is that the power supply output voltages drop, causing the
odd changes to white and black.  The symptoms of having the wrong
power supply voltage vary radically with the type of circuit and which
capacitors are a problem.  I've seen flickering, fades, time delayed
sudden failure, smoke, fire, and most commonly, just plain no picture..
Given a specific single component failure, it's possible to predict
the symptoms.  Given multiple partial failures, it's at best a guess.

Open up the monitor (it's a royal pain), replace all the big caps
whether they look bad or not, and live happily ever after.  If you're
into being sure, I suggest you look into purchasing or building an ESR
(equivalent series resistance) meter, as you're guaranteed to run into
this problem in other devices that use electrolytics (motherboards,
TV's, power supplies, monitors, game boxes, router, etc).  I use mine
far too often.

http://www.ludens.cl/Electron/esr/esr.html
http://www.anatekcorp.com/blueesr.htm
http://www.flippers.com/esrktmtr.html> (I have this one)
http://www.midwestdevices.com/index.html

More good reading on LCD repair:
http://www.ccl-la.com/blog/index.php/category/monitor-repair/
Note how just about all the failures are electrolytic capacitors.
Here's your Syncmaster 204 page:
http://www.ccl-la.com/blog/index.php/samsung-214t-repair/
Note the they're symptoms include a "dark picture".  Hmmmm...

--
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

Could placing a small 12V fan temporarily, at least, in that area be a
diagnostic tool ?

Yes, I considered this. Unfortunately, as I described, the problem is
very random.  For example, it has not surfaced in over a week.  So by
trying to cool it, I don't know if it's actually helping, or luck.
The same problem applies to the suggestions I've received to replace
the caps outlined on that website.  While I'd be happy to do it, I
won't really know if it has helped for a couple months.

One thing I'd really like is to find a trigger for this problem.  I
will try heat today.  Is there a way to "stress" the monitor's
electronics, to try reproducing the issue?  Would changing the image
rapidly have any effect?  Should I display a solid color (perhaps
white) on it?

With a reasonably reliable repro procedure (even if it takes hours), I
can then get more info, and attempt to fix it, all while having some
confidence that my changes have either helped or not.

So I tried various techniques to try reproducing the problem today,
all to no avail. I tried heat. I displayed a solid white image--with
the brightness & contrast at their max level--for several hours
straight; nothing. I turned it off for ~4 hours, and when I turned it
back on, the problem repeated itself. So clearly heat is not a
trigger, not is prolonged use. Unfortunately, the "randomness" of the
problem persists.

Here's more observations:

When the monitor is in it's "black" state, it's not as if the monitor
was off--there is a very low level of light on the screen, so it's
more of a dark gray than black. Is this the backlight?

With the monitor in it's "gray/black" state, I pointed a flashlight at
the screen at all angles & at a close distance. I do not see any of
the image.

I noticed that as the problem was occurring, and the screen was fading
first to white, and then to gray/black, the image is not being
updated. I moved the mouse over to that screen while the fading was
occurring, but the mouse on that screen did not move. Does this
suggest a defective video board?

I also tried adjusting the brightness & contrast, but I couldn't,
because the on-screen menu does not show up.

 

[Jeff Liebermann]

On Mon, 3 May 2010 20:18:13 -0700 (PDT), saber850 <saber850@yahoo.com>
wrote:

So I tried various techniques to try reproducing the problem today,
all to no avail.

I don't mean to be overly critical, but I think I see a problem. You
remind me of something I had to deal with when training technicians in
a past life. I referred to it as "Circle the wagons. The Indians are
attacking". This was in reference to the tendency for some techs to
march around the problem area, gain a little more insight, but burn
huge amounts of time going literally in circles. The Indians never
had a chance, after tiring their horses, by going in circles around
the wagons. Both you and the attacking Indians would be far more
effective with a direct assault on the problem. At some point, you
will need to dive into the LCD monitor and get your hands dirty. No
amount of additional insight or diagnostics are going to prevent this
from happening. Even if you isolate the problem to a single capacitor
and totally undestand the failure mechanism, you'll still need to
crack the case and do the necessary parts replacement. Might as well
get it over with now (before your horse gets tired).
<http://www.ccl-la.com/blog/index.php/samsung-214t-repair/>


--
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

 

[William Sommerwerck]

So I tried various techniques to try reproducing the problem today,
all to no avail.

I don't mean to be overly critical, but I think I see a problem. You
remind me of something I had to deal with when training technicians
in a past life. I referred to it as "Circle the wagons. The Indians are
attacking". This was in reference to the tendency for some techs to
march around the problem area, gain a little more insight, but burn
huge amounts of time going literally in circles. The Indians never
had a chance, after tiring their horses, by going in circles around
the wagons. Both you and the attacking Indians would be far more
effective with a direct assault on the problem. At some point, you
will need to dive into the LCD monitor and get your hands dirty. No
amount of additional insight or diagnostics are going to prevent this
from happening. Even if you isolate the problem to a single capacitor
and totally undestand the failure mechanism, you'll still need to
crack the case and do the necessary parts replacement. Might
as well get it over with now (before your horse gets tired).
http://www.ccl-la.com/blog/index.php/samsung-214t-repair

Excellent points, that need to be repeated often.

They're related to the issue of whether you're trying to figure out exactly
what's wrong, or simply getting the unit working again. Often (too often),
you have to abandon the analysis, and "dig in".

My guess is that this problem is related to the power-supply voltages for
the video driver circuits. Second guess would be a bad video driver. (I
don't know whether it's a board or a single chip in this unit.)

 

[Meat Plow]

On Tue, 04 May 2010 09:37:48 -0700, Jeff Liebermann
<jeffl@cruzio.com>wrote:

On Mon, 3 May 2010 20:18:13 -0700 (PDT), saber850 <saber850@yahoo.com
wrote:

So I tried various techniques to try reproducing the problem today,
all to no avail.

I don't mean to be overly critical, but I think I see a problem. You
remind me of something I had to deal with when training technicians in
a past life. I referred to it as "Circle the wagons. The Indians are
attacking". This was in reference to the tendency for some techs to
march around the problem area, gain a little more insight, but burn
huge amounts of time going literally in circles. The Indians never
had a chance, after tiring their horses, by going in circles around
the wagons. Both you and the attacking Indians would be far more
effective with a direct assault on the problem. At some point, you
will need to dive into the LCD monitor and get your hands dirty. No
amount of additional insight or diagnostics are going to prevent this
from happening. Even if you isolate the problem to a single capacitor
and totally undestand the failure mechanism, you'll still need to
crack the case and do the necessary parts replacement. Might as well
get it over with now (before your horse gets tired).
http://www.ccl-la.com/blog/index.php/samsung-214t-repair/

<applause>

 

[saber850]

On May 4, 12:57 pm, "William Sommerwerck" <grizzledgee...@comcast.net>
wrote:

So I tried various techniques to try reproducing the problem today,
all to no avail.
I don't mean to be overly critical, but I think I see a problem. You
remind me of something I had to deal with when training technicians
in a past life. I referred to it as "Circle the wagons. The Indians are
attacking". This was in reference to the tendency for some techs to
march around the problem area, gain a little more insight, but burn
huge amounts of time going literally in circles. The Indians never
had a chance, after tiring their horses, by going in circles around
the wagons. Both you and the attacking Indians would be far more
effective with a direct assault on the problem. At some point, you
will need to dive into the LCD monitor and get your hands dirty. No
amount of additional insight or diagnostics are going to prevent this
from happening. Even if you isolate the problem to a single capacitor
and totally undestand the failure mechanism, you'll still need to
crack the case and do the necessary parts replacement. Might
as well get it over with now (before your horse gets tired).
http://www.ccl-la.com/blog/index.php/samsung-214t-repair

Excellent points, that need to be repeated often.

They're related to the issue of whether you're trying to figure out exactly
what's wrong, or simply getting the unit working again. Often (too often),
you have to abandon the analysis, and "dig in".

My guess is that this problem is related to the power-supply voltages for
the video driver circuits. Second guess would be a bad video driver. (I
don't know whether it's a board or a single chip in this unit.)

Yes, I understand your point.

I think I'm more apt to approach this cautiously for several reasons.

One is that I don't have an urgent need to address the problem. This
is partly due to my other monitor working fine, and also because the
monitor does not malfunction frequently or for extended periods of
time (a couple hours of downtime over several weeks).

Another reason is that I'm not very knowledgeable or experienced on
this type of problem, so I'm ramping up quite a bit.

Yet another reason is that I'm a big proponent of measure twice, cut
once. From what I've read, opening the case isn't simple, and will
likely lead to blemishes. So I'd prefer to minimize the number of
times I have to open it, which can be accomplished by having some
confidence in the problem & solution. I understand that I won't know
or understand every detail. But I don't think knowledge will hurt,
and I'm not in a rush.

So given this list, I find it reasonable to perform some extra
diligence and learn a lot that I don't know, before digging in. I
realize some people have suggested that the caps are a common problem
w/ this monitor, but their problem doesn't seem to be the same as
mine. And I'd prefer to avoid unnecessary de-soldering & soldering,
given that I can actually make things worse. Given the symptoms of
the problem and all that I've learned from this group and the web, I'm
inclined to think the problem is the video board. But since I need to
open the case to get the video board's part & rev numbers, I'll have a
chance to inspect the caps before proceeding.

Thanks to everyone for your help, I really appreciate it. I'll post
back w/ my progress.

 

[Jeff Liebermann]

On Tue, 4 May 2010 20:15:46 -0700 (PDT), saber850 <saber850@yahoo.com>
wrote:

http://www.ccl-la.com/blog/index.php/samsung-214t-repair

I opened the case and analyzed all the caps--none are bulging or
leaking/oozing.

One small step... etc.

Look at the photos in:
<http://www.ccl-la.com/blog/index.php/samsung-214t-repair>
Do you see any bulging or leaks? Nope. Not all caps fail with
obvious physical evidence. That's where the ESR meter is used. You
can test the capacitors without removing them from the circuit.
Lacking that, just get some replacement caps, replace everything
listed in the article, and it should be back to working.

As for a better understanding of what's happening, it's difficult
enough to analyzer a circuit when all the parts are within normal
design limits. However, if you want to see what happens when you
insert a defective capacitor into the circuit, download a free copy of
LTSpice (formerly known as SwitcherCAD),
<http://www.linear.com/designtools/software/>
and buy a collection of SPICE switcher models:
<http://pagesperso-orange.fr/cbasso/Spice.htm>
<http://pagesperso-orange.fr/cbasso/Downloads/LTSpice/PWM%20Switch%20LTSpice.zip>
The author suggests you need the book to understand the models. I
agree.

Get the program working with a proper switching power supply. It
doesn't have to be exactly the same as the Samsung monitor. Then cram
in the equivalent of a bad capacitor, which would be a normal
capacitor, with the same capacitance value as on the label, but with
an added series resistance equal to about 2-5 times maximum ESR.
<http://members.ozemail.com.au/~bobpar/2003esrchart.txt>
<http://members.ozemail.com.au/~bobpar/graph1.gif>
<http://members.ozemail.com.au/~bobpar/graph2.gif>
<http://members.ozemail.com.au/~bobpar/graph3.gif>

A subtle hint is that with a switching power supply, the output
voltage almost never goes up when a component fails. It either goes
down, or massive amounts of high frequency ripple appears on the
output. How the rest of the LCD monitor responds to this is a bit of
a guess. Usually, it just shuts down, resulting in a black display.

Also, I forgot to caution you to *NOT* constantly power cycle the
monitor in an attempt to revive the circuit. It's bad enough having
the capacitors blow up. There's a chance that the associated
switching transistors will not appreciate the added load (which is
what's heating the capacitors) and blow up. For example, this loser
of a Dell monitor:
<http://www.ccl-la.com/blog/index.php/dell-e173fpb-17lcd-repair/>
usually takes out 6 xsistors, a diode, and anywhere between one and
eight electrolytics. I once tried to fix one, and didn't catch one of
the caps. Within a week, all 6 transistors were again blown.

Also, if you read the above instructions carefully, note that it
mentions resoldering the xformer leads. I do this whether it needs it
or not. What happens is that the xformers operate at about 40KHz(?).
Some of this 40KHz energy is transfered to the xformer leads,
resulting in cracked solder. It's very difficult to see without a
microscope. It was a problem with Tin-Lead solder but is really a
PITA with brittle ROHS Tin-Silver solder. The same thing can happen
at audio frequencies:
<http://www.clarkeaudio.com/nfinfo.htm>

Anyway, your next ordeal will be selecting the proper replacement
capacitors from the Digikey or Mouser online order pages. It's very
easy to pick the wrong part. Be careful, or ask for help. Also, buy
some spares. My prediction is that your matching monitor will soon
have the same problem.

--
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

 

[saber850]

On May 4, 9:44 pm, saber850 <saber...@yahoo.com> wrote:

On May 4, 12:57 pm, "William Sommerwerck" <grizzledgee...@comcast.net
wrote:



So I tried various techniques to try reproducing the problem today,
all to no avail.
I don't mean to be overly critical, but I think I see a problem. You
remind me of something I had to deal with when training technicians
in a past life. I referred to it as "Circle the wagons. The Indians are
attacking". This was in reference to the tendency for some techs to
march around the problem area, gain a little more insight, but burn
huge amounts of time going literally in circles. The Indians never
had a chance, after tiring their horses, by going in circles around
the wagons. Both you and the attacking Indians would be far more
effective with a direct assault on the problem. At some point, you
will need to dive into the LCD monitor and get your hands dirty. No
amount of additional insight or diagnostics are going to prevent this
from happening. Even if you isolate the problem to a single capacitor
and totally undestand the failure mechanism, you'll still need to
crack the case and do the necessary parts replacement. Might
as well get it over with now (before your horse gets tired).
http://www.ccl-la.com/blog/index.php/samsung-214t-repair

Excellent points, that need to be repeated often.

They're related to the issue of whether you're trying to figure out exactly
what's wrong, or simply getting the unit working again. Often (too often),
you have to abandon the analysis, and "dig in".

My guess is that this problem is related to the power-supply voltages for
the video driver circuits. Second guess would be a bad video driver. (I
don't know whether it's a board or a single chip in this unit.)

Yes, I understand your point.

I think I'm more apt to approach this cautiously for several reasons.

One is that I don't have an urgent need to address the problem.  This
is partly due to my other monitor working fine, and also because the
monitor does not malfunction frequently or for extended periods of
time (a couple hours of downtime over several weeks).

Another reason is that I'm not very knowledgeable or experienced on
this type of problem, so I'm ramping up quite a bit.

Yet another reason is that I'm a big proponent of measure twice, cut
once.  From what I've read, opening the case isn't simple, and will
likely lead to blemishes.  So I'd prefer to minimize the number of
times I have to open it, which can be accomplished by having some
confidence in the problem & solution.  I understand that I won't know
or understand every detail.  But I don't think knowledge will hurt,
and I'm not in a rush.

So given this list, I find it reasonable to perform some extra
diligence and learn a lot that I don't know, before digging in.  I
realize some people have suggested that the caps are a common problem
w/ this monitor, but their problem doesn't seem to be the same as
mine.  And I'd prefer to avoid unnecessary de-soldering & soldering,
given that I can actually make things worse.  Given the symptoms of
the problem and all that I've learned from this group and the web, I'm
inclined to think the problem is the video board.  But since I need to
open the case to get the video board's part & rev numbers, I'll have a
chance to inspect the caps before proceeding.

Thanks to everyone for your help, I really appreciate it.  I'll post
back w/ my progress.

I opened the case and analyzed all the caps--none are bulging or
leaking/oozing.

 

[saber850]

On May 5, 12:12 am, Jeff Liebermann <je...@cruzio.com> wrote:

On Tue, 4 May 2010 20:15:46 -0700 (PDT), saber850 <saber...@yahoo.com
wrote:

http://www.ccl-la.com/blog/index.php/samsung-214t-repair
I opened the case and analyzed all the caps--none are bulging or
leaking/oozing.

One small step... etc.

Look at the photos in:
http://www.ccl-la.com/blog/index.php/samsung-214t-repair
Do you see any bulging or leaks?  Nope.  Not all caps fail with
obvious physical evidence.  That's where the ESR meter is used.  You
can test the capacitors without removing them from the circuit.
Lacking that, just get some replacement caps, replace everything
listed in the article, and it should be back to working.

As for a better understanding of what's happening, it's difficult
enough to analyzer a circuit when all the parts are within normal
design limits.  However, if you want to see what happens when you
insert a defective capacitor into the circuit, download a free copy of
LTSpice (formerly known as SwitcherCAD),
http://www.linear.com/designtools/software/
and buy a collection of SPICE switcher models:
http://pagesperso-orange.fr/cbasso/Spice.htm
http://pagesperso-orange.fr/cbasso/Downloads/LTSpice/PWM%20Switch%20L...
The author suggests you need the book to understand the models.  I
agree.

Get the program working with a proper switching power supply.  It
doesn't have to be exactly the same as the Samsung monitor.  Then cram
in the equivalent of a bad capacitor, which would be a normal
capacitor, with the same capacitance value as on the label, but with
an added series resistance equal to about 2-5 times maximum ESR.
http://members.ozemail.com.au/~bobpar/2003esrchart.txt
http://members.ozemail.com.au/~bobpar/graph1.gif
http://members.ozemail.com.au/~bobpar/graph2.gif
http://members.ozemail.com.au/~bobpar/graph3.gif

A subtle hint is that with a switching power supply, the output
voltage almost never goes up when a component fails.  It either goes
down, or massive amounts of high frequency ripple appears on the
output.  How the rest of the LCD monitor responds to this is a bit of
a guess.  Usually, it just shuts down, resulting in a black display.

Also, I forgot to caution you to *NOT* constantly power cycle the
monitor in an attempt to revive the circuit.  It's bad enough having
the capacitors blow up.  There's a chance that the associated
switching transistors will not appreciate the added load (which is
what's heating the capacitors) and blow up.  For example, this loser
of a Dell monitor:
http://www.ccl-la.com/blog/index.php/dell-e173fpb-17lcd-repair/
usually takes out 6 xsistors, a diode, and anywhere between one and
eight electrolytics.  I once tried to fix one, and didn't catch one of
the caps.  Within a week, all 6 transistors were again blown.

Also, if you read the above instructions carefully, note that it
mentions resoldering the xformer leads.  I do this whether it needs it
or not.  What happens is that the xformers operate at about 40KHz(?).
Some of this 40KHz energy is transfered to the xformer leads,
resulting in cracked solder.  It's very difficult to see without a
microscope.  It was a problem with Tin-Lead solder but is really a
PITA with brittle ROHS Tin-Silver solder.  The same thing can happen
at audio frequencies:
http://www.clarkeaudio.com/nfinfo.htm

Anyway, your next ordeal will be selecting the proper replacement
capacitors from the Digikey or Mouser online order pages.  It's very
easy to pick the wrong part.  Be careful, or ask for help.  Also, buy
some spares.  My prediction is that your matching monitor will soon
have the same problem.

--
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

Thanks. Is there a particular brand of caps which is considered the
best? From my reading, I should stay away from CapXon (which is what
the Samsung monitor uses).

 

[Jeff Liebermann]

On Thu, 6 May 2010 17:18:36 -0700 (PDT), saber850 <saber850@yahoo.com>
wrote:

Thanks. Is there a particular brand of caps which is considered the
best? From my reading, I should stay away from CapXon (which is what
the Samsung monitor uses).

Looking at my inventory, I've been using Panasonic-ECG, type A, Series
NHG, with 105C temperature ratings. For example, the Digikey part
number for 1000UF/16v is P5533-ND
<http://industrial.panasonic.com/www-data/pdf/ABA0000/ABA0000CE26.pdf>
<http://dkc3.digikey.com/PDF/US2010/P1643.pdf>

If you want to avoid the problem entirely, search for Polymer
Capacitors, which don't have any electrolyte. Fujitsu, UCC, and Oscon
make those.
<http://www.fpcap.jp/en/products/index.html>

I just tried to fix a Samsung Syncmaster 192N monitor. I replaced 6
assorted CapXon electrolytics but the monitor doesn't work. My ESR
meter is at home so I'll drag the pile home and report on the measured
ESR values. A bit of Googling seems to indicate the CapXon are junk.

More:
<http://pavel.kirkovsky.com/2009/03/samsung-syncmaster-204b-repair/>

--
# 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]

On Thu, 06 May 2010 21:25:00 -0700, Jeff Liebermann <jeffl@cruzio.com>
wrote:

I just tried to fix a Samsung Syncmaster 192N monitor. I replaced 6
assorted CapXon electrolytics but the monitor doesn't work. My ESR
meter is at home so I'll drag the pile home and report on the measured
ESR values.

Hmmm... Weird and not according to my guesswork, as usual.

Value Max ESR Measured ESR
1000uF 25v 0.10 0.08
1000uF 25v 0.10 0.07
1000uF 10v 0.10 0.12
1000uF 10v 0.10 0.08
330uF 25v 0.30 0.10
330uF 25v 0.30 0.10

Max ESR from this chart:
<http://members.ozemail.com.au/~bobpar/2003esrchart.txt>

Out of 6 caps removed and tested, only one of them is somewhat bad. No
wonder replacing the caps didn't fix the monitor. Something else is
wrong. So much for the easy fix.

--
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

 

[Dav.p.]

Hi, i'm new here and sorry 4 my poor english, first of all this long flame seems to me much
out of site (? exagerate..?), too much word maybe for a very simple problem, i'm not a tech
but from the first agree with talks of J.Liebermann, the strange thing i spect from somone that
suspected the main 5v line that ususally supply the graphic/video chip, so is not (for me) a bad
idea to test the 5v line on the psu connector to the v.board since you don't found any bulged/
dirt capacitor, and if you find the v changes according to the fades then go to order caps, if not
try at least to measure on the regulator on v.board to see if exit 3,3v fixed or some like it.
I don't agree to what said, it's a luck that you have 2 equal monitor so in the last if you don't
find culprit you can swap boards and see

bye bye.

 

[Dav.p.]

but from the first agree with talks of J.Liebermann, the strange thing i spect from somone that

sorry, i espected... i've made a jam.. the strange thing was: nobody has told to test 5v line..

suspected the main 5v line that ususally supply the graphic/video chip, so is not (for me) a bad
idea to test the 5v line on the psu connector to the v.board since you don't found any bulged/

 

[saber850]

On May 7, 9:06 pm, "Dav.p." <davi...@tiscali.it> wrote:

Hi, i'm new here and sorry 4 my poor english, first of all this long flame seems to me much
out of site (? exagerate..?), too much word maybe for a very simple problem, i'm not a tech
but from the first agree with talks of  J.Liebermann, the strange thing i spect from somone that
suspected the main 5v line that ususally supply the graphic/video chip, so is not (for me) a bad
idea to test the 5v line on the psu connector to the v.board since you don't found any bulged/
dirt capacitor, and if you find the v changes according to the fades then go to order caps, if not
try at least to measure on the regulator on v.board to see if exit 3,3v fixed or some like it.
I don't agree to what said, it's a luck that you have 2 equal monitor so in the last if you don't
find culprit you can swap boards and see

bye bye.

Yes, I've been considering swapping one of the boards between the
monitors. This seems like the easiest way to narrow down the problem.

 

[Dav.p.]

is also the last way, control first out voltages, if bad change caps

 

[Jeff Liebermann]

On Sun, 9 May 2010 15:04:59 -0700 (PDT), saber850 <saber850@yahoo.com>
wrote:

Are the Polymer caps
entirely superior to electrolyte ones? Are there drawbacks to polymer
caps?

This article covers most everything:
<http://www.capacitorlab.com/capacitor-types-polymer/>
Polymer caps solve just about every complaint I can think of with
electrolytics. The major benefits are much longer lifetime, lower
ESR, and better temp stability. The down sides are the higher cost
and that they are available only in fairly low voltages.

If you can find them, and can afford the cost, do it.



--
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

 

[saber850]

On May 9, 11:12 am, saber850 <saber...@yahoo.com> wrote:

On May 7, 9:06 pm, "Dav.p." <davi...@tiscali.it> wrote:

Hi, i'm new here and sorry 4 my poor english, first of all this long flame seems to me much
out of site (? exagerate..?), too much word maybe for a very simple problem, i'm not a tech
but from the first agree with talks of  J.Liebermann, the strange thing i spect from somone that
suspected the main 5v line that ususally supply the graphic/video chip, so is not (for me) a bad
idea to test the 5v line on the psu connector to the v.board since you don't found any bulged/
dirt capacitor, and if you find the v changes according to the fades then go to order caps, if not
try at least to measure on the regulator on v.board to see if exit 3,3v fixed or some like it.
I don't agree to what said, it's a luck that you have 2 equal monitor so in the last if you don't
find culprit you can swap boards and see

bye bye.

Yes, I've been considering swapping one of the boards between the
monitors.  This seems like the easiest way to narrow down the problem.

I swapped the power boards in the monitors. The "good" monitor
immediately exhibited the problem that the previously malfunctioning
one did, while the "bad" monitor works fine (at least, so far). So
I'm confident that the problem is from the power board, and given this
thread and some web sites, I'll start w/ the caps. Now that I had
both power boards to examine, I also noticed that the C110 and C111
caps were replaced by Samsung when I sent the monitor in for repair
earlier this year (the last month of its warranty). I'll get the
specs of all caps today, find corresponding parts on DigiKey, and post
back here for confirmation.

I will research this topic on the web, but are the Polymer caps
entirely superior to electrolyte ones? Are there drawbacks to polymer
caps?

 

[Dav.p.]

one did, while the "bad" monitor works fine (at least, so far). So

you say the bad mon. with the good power board i think...

I'm confident that the problem is from the power board, and given this

ok, 1-0 for me...
(ah it's a soccer score sorry..)

both power boards to examine, I also noticed that the C110 and C111
caps were replaced by Samsung when I sent the monitor in for repair

from what you noticed? The shining solderings?

earlier this year (the last month of its warranty). I'll get the
specs of all caps today, find corresponding parts on DigiKey, and post
back here for confirmation.

i think is not so vital to find the specs, only take uF and V and order a good brand of low esr type. (105c)

I will research this topic on the web, but are the Polymer caps
entirely superior to electrolyte ones? Are there drawbacks to polymer
caps?

As above i'm not an expert at all but i think.. with a good brand like Sanyo, Rubycon, Panasonic
etc, you can go quiet and live life in peace for at least 3-4 years intense-use,
it's a good idea replace all area's caps, to be sure.. like i said it's safer and instructive
to test the 5v line output for instability, or the 12v if 5v is stable.. but it is no so safe whitout
precautions so it's up to you, if the boards stays screwed on the back and face outside is more
safe.

 

[saber850]

On May 9, 11:00 pm, "Dav.p." <davi...@tiscali.it> wrote:

one did, while the "bad" monitor works fine (at least, so far).  So

you say the bad mon. with the good power board i think...

I'm confident that the problem is from the power board, and given this

ok, 1-0 for me...  
(ah it's a soccer score sorry..)

both power boards to examine, I also noticed that the C110 and C111
caps were replaced by Samsung when I sent the monitor in for repair

from what you noticed? The shining solderings?

earlier this year (the last month of its warranty).  I'll get the
specs of all caps today, find corresponding parts on DigiKey, and post
back here for confirmation.

i think is not so vital to find the specs, only take uF and V and order a good brand of low esr type. (105c)

I will research this topic on the web, but are the Polymer caps
entirely superior to electrolyte ones?  Are there drawbacks to polymer
caps?

As above i'm not an expert at all but i think.. with a good brand like Sanyo, Rubycon, Panasonic
etc, you can go quiet and live life in peace for at least 3-4 years intense-use,
it's a good idea replace all area's caps, to be sure.. like i said it's safer and instructive
to test the 5v line output for instability, or the 12v if 5v is stable.. but it is no so safe whitout
precautions so it's up to you, if the boards stays screwed on the back and face outside is more
safe.

Yes, I'm confident the the problem is w/ the power board, since that's
the only thing that changed, and the problem followed it. The monitor
w/ the power board from the non-malfunctioning monitor has been
functioning properly for 24 hours.

There are three reasons that I suspect the C110 and C111 caps were
replaced. The first reason is that all caps across both power boards
except those two have a hand-drawn black mark (line on the radius) on
top. Those two have slightly shinier solder. And there are small
scratches on the underside of the PCB around those caps' pins.

As for testing the 5V or 12V lines, that's not easy because the boards
are not screwed down. There is a metal plate which sandwiches these
boards to the back of the panel, and which provides the mounting
point.

 

[Jeff Liebermann]

On Mon, 10 May 2010 13:32:47 -0700 (PDT), saber850
<saber850@yahoo.com> wrote:

PCB Designation Farads (ľF) Voltage (V) Temp (C) Length (mm)
Potential Length (mm) Diameter (mm) Lead Spacing (Board) (mm) Mouser
Replacement Mouser Replacement URL

C105 150 450 105 41 45 20 7 661-EKMQ451VN151MP40
http://www.mouser.com/Search/ProductDetail.aspx?R=EKMQ451VN151MP40Svirtualkey66100000virtualkey661-EKMQ451VN151MP40

You probably do NOT need to replace the big 150uF/450V capacitor. It's
not the high voltage low ripple current capacitors that fail. It's the
low voltage, but high ripple current filter caps that get hot and blow
up.

C107 47 50 105 11 24 5 5 667-ECA-1HHG470
http://www.mouser.com/Search/ProductDetail.aspx?R=ECA-1HHG470virtualkey66720000virtualkey667-ECA-1HHG470

Tolerable. It's not a low ESR type, but it's low enough to work.

C301 680 25 105 17 22 10 5 667-EEU-FC1E681
http://www.mouser.com/Search/ProductDetail.aspx?R=EEU-FC1E681virtualkey66720000virtualkey667-EEU-FC1E681
C302 680 25 105 17 22 10 5 667-EEU-FC1E681
http://www.mouser.com/Search/ProductDetail.aspx?R=EEU-FC1E681virtualkey66720000virtualkey667-EEU-FC1E681

It's low-ESR (although the data sheet doesn't clearly show this) so it
will work.

C110 820 25 105 22 24 10 5 598-361R821M025EG0E
http://www.mouser.com/Search/ProductDetail.aspx?R=361R821M025EG0Evirtualkey59850000virtualkey598-361R821M025EG0E
C111 820 25 105 22 24 10 5 598-361R821M025EG0E
http://www.mouser.com/Search/ProductDetail.aspx?R=361R821M025EG0Evirtualkey59850000virtualkey598-361R821M025EG0E

Also low-ESR and good quality cap. No problems.

C112 330 25 105 14 24 10 5 667-EEU-FC1E331
http://www.mouser.com/Search/ProductDetail.aspx?R=EEU-FC1E331virtualkey66720000virtualkey667-EEU-FC1E331

Looks generally ok.

I'll leave it to you to determine if the case sizes and lead spacing
are the same as the originals. Neither is particularly critical as
there is usually plenty of room. One suggestion is to use the next
higher voltage rating capacitor. The 50v cap will probably remain
50v, but the 25v caps should be replaced with 35v caps. They last
longer, have a lower ESR, and aren't that much larger.

--
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