Author Topic: bad caps on samsung lcd display  (Read 14987 times)

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Online David Hess

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Re: bad caps on samsung lcd display
« Reply #25 on: July 10, 2014, 05:10:41 pm »
What are the expected side effects of higher ESR, and of lower ripple current rating?

Higher ESR results in higher output ripple but counter intuitively it also usually increases the phase margin making the regulator more stable. 

Higher ESR also results in higher temperature operation because at a given ripple current, more power will be dissipated by the capacitor.  The higher temperature lowers the operating life.  This is reflected in the ripple current rating which will be lower and is the reason why low a ESR is associated with a high ripple current rating.

It is sometimes necessary to use multiple capacitors in parallel to achieve a high ripple current rating.  Multiple small capacitors are often better than fewer large ones because their greater surface area for a given volume allows greater heat dissipation capability.
 

Offline lpc32

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Re: bad caps on samsung lcd display
« Reply #26 on: July 16, 2014, 01:21:36 am »
Thanks.
 

Offline HighVoltage

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Re: bad caps on samsung lcd display
« Reply #27 on: July 17, 2014, 07:28:05 am »
One of the best Samsung monitors from the early flat screen days is the SyncMaster 214T
They sold for almost $2000 in those days.
And the beauty is that you can get them for almost free, when they are broken.
And each and every time, the problem was in the ESR of the Caps

It is unreal to me, that a company like Samsung would deploy bad caps for such a long time
It seems we are talking now of a period from 8 to 10 years of bad caps in SyncMaster screens
There are 3 kinds of people in this world, those who can count and those who can not.
 

Offline linux-worksTopic starter

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Re: bad caps on samsung lcd display
« Reply #28 on: July 17, 2014, 06:38:26 pm »
the more I talk to folks who have dealt with samsung, the more I hear this thing coming up again and again.

samsung designs things so that they last JUST as long as the warranty and no more.  almost to a science.

I like samsung ssd's but I'm going to try to avoid that company for all other things if I can help it.  I see a trend, here, in the corporate culture.  I've heard and read too much about samsung for it to be a one-off problem.

Offline SeanB

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Re: bad caps on samsung lcd display
« Reply #29 on: July 17, 2014, 06:45:27 pm »
2 Samsung 24 inch monitors, bought new and with a 5 year warranty. Both failed about 2 weeks out of warranty. One was left running 24/7/365 and the other was switched off ( with a real power switch on the front of the unit, no soft switch here) at the end of each day. In both units the line output transistor was shorted, due to the line output transformer breaking down. The LOPT was no longer available as a spare part ( though I could actually get the 24 inch CRT complete with scan coils as a spare and they had stock of it) as it had been discontinued 4 years ago. Apparently they simply gave you a new monitor of the same or next bigger size if they failed under warranty and it was not a dead CRT. Burns were not covered, and these large CRT's were very easy to burn if you left the brightness high with a static image.
 

Offline P90

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Re: bad caps on samsung lcd display
« Reply #30 on: September 12, 2014, 02:26:25 am »
I just fixed an LG monitor that had 3 bad CapXon caps. $3 and up and running again! woohooo!  :)
 

Offline Bud

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Re: bad caps on samsung lcd display
« Reply #31 on: September 28, 2014, 06:12:05 pm »
it seems this model (Samsung 225BW) is nothing BUT trouble;

Hmmm.... The one I am using typing this message is I think 7 years old, still working fine

Facebook-free life and Rigol-free shack.
 

Offline PlaneSailing

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Re: bad caps on samsung lcd display
« Reply #32 on: November 16, 2024, 11:53:34 pm »
Hello, looking for advice fixing my (nice when working) 2007 Samsung SyncMaster 226bw.
   Problem is after power on, top left screen shows the digital then analog box for a couple of seconds, then nothing, same issue after pressing the source button. Shining a strong flashlight at the screen, the "check signal cable" box can be seen moving about the screen, so looks like the backlight power supply (or control of it) has failed ?, but the backlights themselves are probably OK ?.

   Inside C113, a 330uF 25V SamWHA ? brand was bulging, replaced it with a 0.15 Ohm ESR new capacitor  - the same problem.  Replaced all 5 820uF with new 0.1 Ohm ESR Panasonic caps - the same problem. Replaced the 3 smaller capacitors (47uf, 22uf and 2.2uF) with no luck. Using a scope and 10" of wire soldered to the "13.5V" pins on the power connector showed a steady 15.6V with 100mV of 200kHz switching signal - not too unexpected. The ON/OFF line on the power connector is 0V when the monitor if off, and a steady 2.5V when on. The A-DIM and B-DIM lines are both about 0V with 50mV of noise, a bit less noise when the backlight is off. Seems a bit strange.....  but it's the same when the backlight is on or off.

   I'm at a loss - maybe something has gone wrong on the high voltage side of the power board ?, appreciate advice, maybe retry with new capacitors ?, or I just buy a new (old but "working") power board on eBay ?, thanks.

   
 

Online wraper

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Re: bad caps on samsung lcd display
« Reply #33 on: November 17, 2024, 12:05:55 am »
^With such problem - bad capacitors (most likely), bad ccfl transformer (measure secondary winding(s) resistance), or bad backlight lamp.
« Last Edit: November 17, 2024, 12:09:08 am by wraper »
 
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Offline PlaneSailing

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Re: bad caps on samsung lcd display
« Reply #34 on: November 25, 2024, 06:56:46 pm »
Thanks wrapper for your reply. I have replaced all of the electrolytics on the power board with new low ESR caps.  The backlight works for 2 seconds after power on and also works for 2 seconds after pressing the "source" button, so I "think" the capacitors, transformer and backlight lamp are OK ?.  Appreciate if anyone has seen this symptom before or has idea, thanks.
 

Online wraper

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Re: bad caps on samsung lcd display
« Reply #35 on: November 25, 2024, 07:07:37 pm »
The backlight works for 2 seconds after power on and also works for 2 seconds after pressing the "source" button, so I "think" the capacitors, transformer and backlight lamp are OK
No, it means that backlight driver protection kicks in and it can be due to either of those reasons. Backlight lighting up for a moment does not mean those are good, it only means they're good enough for at least one of the CCFLs to light up before protection circuit notices an issue and shuts it down.
 

Offline PlaneSailing

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Re: bad caps on samsung lcd display
« Reply #36 on: December 18, 2024, 07:28:15 pm »
   Update: The replacement (sold on eBay as "working") IP-43130A power supply arrived, put it in my 226bw and the same symptoms as the recapped original supply. The backlight comes on dimly ? for just a couple of seconds after power on, or pressing the "source" button. One time it stayed on for 10 seconds with much "sizzling" sounds.  My suspicion is the CCFL backlight(s?) have gone ?, and/or is tripping the power supply into shutting down ?. Believe the set has 2 lights - one top and one bottom ?, fed from the 4 dual cables from the high voltage side of the supply. Removing these cables in all sort of arrangements did not help, as long as a pair (so 4 wires) from the top or bottom were connected the display would come on for just 2 seconds after power on.  Maybe both bulbs have gone ?.  Appreciate any advice on the bulb part number and how to get them ?, or is the whole display now unfortunately "recycle material" ?, thanks.
 

Online wraper

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Re: bad caps on samsung lcd display
« Reply #37 on: December 18, 2024, 07:43:07 pm »
You can replace CCFL but it's not that easy to disassemble and reassemble LCD panel without screwing up. You should search CCFL by display size, not model. Ensure they're of the same dimensions as original lamps.
 
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