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Discussion Starter #1
I have a Samsung LN40A750 for about 2 years now and we have been having a problem with it.


The picture starts off jumbled and then gets better after 10 to 15 minutes.

Sometimes it takes longer.

This has been going on for a few months now.


I don't have the money for a new TV yet and I'm wondering if it is fixable and what the cost might be?


ANY help is appreciated!


Here are some pics of the issue:
TV just powered ON




TV after a few minutes



TV finally back to normal
 

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I tell Samsung owners who are having difficulties with start up to call Samsung customer service, get the serial number off the side of your tv, and see if your tv is one of the many covered by their free, out of warranty, power board replacement. They've had so many problem with the capacitors on the boards going out that they authorized the out of warranty repair.


If your serial number is on their list, they send a repair person to replace the board for free. I think the A series is included.
 

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Discussion Starter #3

Quote:
Originally Posted by mes444 /forum/post/20881502


I tell Samsung owners who are having difficulties with start up to call Samsung customer service, get the serial number off the side of your tv, and see if your tv is one of the many covered by their free, out of warranty, power board replacement. They've had so many problem with the capacitors on the boards going out that they authorized the out of warranty repair.


If your serial number is on their list, they send a repair person to replace the board for free. I think the A series is included.

It's not a startup issue though.

It powers on just fine. Problem is just how the video looks after it turns on.


Is the Video problem a symptom associated with the power board problem?
 

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Many odd problems have been reported by people with failing power boards. Check the link below for a complete description, and below the article, many posters have added their input.


As you can see from the list of effected tvs, the A's are included. It doesn't hurt anything to get the board replaced, it's free and it can possibly fix your problem.

http://www.crovean.net/samsung-lcd-tv-power-up-problem
 

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Discussion Starter #5

Quote:
Originally Posted by mes444 /forum/post/20885221


Many odd problems have been reported by people with failing power boards. Check the link below for a complete description, and below the article, many posters have added their input.


As you can see from the list of effected tvs, the A's are included. It doesn't hurt anything to get the board replaced, it's free and it can possibly fix your problem.

http://www.crovean.net/samsung-lcd-tv-power-up-problem

Called Samsung.

They told me some tests to run and gave a me a service center location info.


But he pretty much said it's not the power board since it is turning on okay.
 

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Quote:
Originally Posted by Majoram /forum/post/20885304


Called Samsung.

They told me some tests to run and gave a me a service center location info.


But he pretty much said it's not the power board since it is turning on okay.

The symptoms you described is EXACTLY how the bad capacitors cause the problem!


This happens all the time on all power supply boards that are of high density, capacitors are located near heat sinks that radiate heat, the capacitors themselves are underrated (in Volts) AND improper type that cannot deal with high frequency ripple found in switching mode power supplies, the whole power supply gets warm... and what not. This causes the electrolyte inside the capacitors to dry, the capacitors lose capacitance and start "injecting" high frequency ripple into DC power supply rails. This upsets the processing sections EVERYWHERE in the TV.


On cold start-up, the above is most obviously shown... the capacitance "restores" as the capacitor start to heat-up.


There's possibility that you have a cold solder joint as well.... however, this would still be located on the power supply board!


Call again, demand to talk to someone who apart from knowing how to lift the phone knows tiny bit about electronics as well (maybe samsung employs idiots on purpose -> to reject perfectly legitimate claim with their idiotic answers!)


10 years ago I sworn no sumsung product will ever enter my household -> still going strong


Boky
 

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Discussion Starter #7

Quote:
Originally Posted by Extreme_Boky /forum/post/20896305


The symptoms you described is EXACTLY how the bad capacitors cause the problem!


This happens all the time on all power supply boards that are of high density, capacitors are located near heat sinks that radiate heat, the capacitors themselves are underrated (in Volts) AND improper type that cannot deal with high frequency ripple found in switching mode power supplies, the whole power supply gets warm... and what not. This causes the electrolyte inside the capacitors to dry, the capacitors lose capacitance and start "injecting" high frequency ripple into DC power supply rails. This upsets the processing sections EVERYWHERE in the TV.


On cold start-up, the above is most obviously shown... the capacitance "restores" as the capacitor start to heat-up.


There's possibility that you have a cold solder joint as well.... however, this would still be located on the power supply board!


Call again, demand to talk to someone who apart from knowing how to lift the phone knows tiny bit about electronics as well (maybe samsung employs idiots on purpose -> to reject perfectly legitimate claim with their idiotic answers!)


10 years ago I sworn no sumsung product will ever enter my household -> still going strong


Boky

It's been a while but I actually understood that


I'll try again.


Just curious but what brand do you go with?
 

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Discussion Starter #8
Called again. Got someone a little more cooperative but my model is not on their list.

Sigh...


So either I pay or fix it myself.
 

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If you're comfortable soldering, it'll be easy to spot which caps need replacing (they'll be visibly bulged). Otherwise having it fixed should be pretty inexpensive. An in-home visit shouldn't cost more than $150 (plus tax) to fix it (assuming it is of course caps).
 

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Discussion Starter #11
Just an update.


So I opened it up and I couldn't find anything wrong visibly with the caps.

My soldering equipment is quite crappy. So I just tried a little re-soldering of the connections.


It SEEMED like the TV started up faster and cleared up faster but after a day it's back to the usual.


1) Anyone know where a I can buy reasonable Soldering equipment and GOOD replacement CAPS?? I think I will see if replacing them will help.


2) Took some pics, so if anyone can tell me if anything seems wrong, please let me know.








 

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Hi Majoram,


Read my post (#6) again:


"There's possibility that you have a cold solder joint as well.... however, this would still be located on the power supply board!"


… you’ll need solid quality multimeter (the CRO would be nice… Service Manual as well…) and a can of freeze spray.


Good luck,

Boky
 

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Discussion Starter #14

Quote:
Originally Posted by Extreme_Boky /forum/post/20942653


Hi Majoram,


Read my post (#6) again:


"There's possibility that you have a cold solder joint as well.... however, this would still be located on the power supply board!"


… you’ll need solid quality multimeter (the CRO would be nice… Service Manual as well…) and a can of freeze spray.


Good luck,

Boky

Actually your post is why I tried resoldering the joint
Thanks btw!


I think an Oscilloscope/Multimeter may be a bit much.

Rather than ID the faulty joint/cap, I was just going to get a new soldering iron and replace all the capacitors.


I haven't done electronics repair in a while, so I'm a bit out of touch.


I assume the CRO/multimeter is to check the capacitor waveform??

Also, what is Freeze Spray for??

Quote:
Originally Posted by MrBobb /forum/post/20939056


If ur intending to go DIY, here are some reasonably priced good soldering equipment. Don't have to buy the most expensive one, middle-road OK.

http://www.mpja.com/productsdirect.a...item5=17204+TL

Thanks! I was also looking at this one:
http://www.amazon.com/Weller-WLC100-...5919746&sr=1-1


or this one:
http://www.amazon.com/gp/product/B00...cm_cr_asin_lnk


What about the capacitors?

I'm not sure how to tell which are good quality ones.
 

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The problem with the distorted video is not a capacitor problem. This is a panel problem (probably a tab bond). When the problem occurs, try squeezing the top corners of the set and see if the problem goes away. You can also grab opposite corners (top left/bottom right or vice versa) and GENTLY rack the panel. Again, if the problem changes, you will have confirmed a panel problem.
 

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Discussion Starter #16

Quote:
Originally Posted by EG3 /forum/post/20943408


The problem with the distorted video is not a capacitor problem. This is a panel problem (probably a tab bond). When the problem occurs, try squeezing the top corners of the set and see if the problem goes away. You can also grab opposite corners (top left/bottom right or vice versa) and GENTLY rack the panel. Again, if the problem changes, you will have confirmed a panel problem.

What is the tab bond problem? Is it fixable?


Also am I squeezing it with the back plastic cover on or off?
 

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Cover on so you don't accidentally electrocute yourself from high voltage to the back-lights! A tab bond is a panel ribbon cable connection within the frame of the panel. There are some posts on here about some people having some success in correcting the problem at least temporarily. But the fix is only a band-aid type repair. It involves partially disassembling the panel and placing a cushion over the affected tab bond. Try searching for some Sony LCD posts by OnlyTono. Perhaps some other members here have some other ideas, resources, or links.


Start here: http://www.avsforum.com/avs-vb/showthread.php?t=1173106
 

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Discussion Starter #18

Quote:
Originally Posted by EG3 /forum/post/20943615


Cover on so you don't accidentally electrocute yourself from high voltage to the back-lights! A tab bond is a panel ribbon cable connection within the frame of the panel. There are some posts on here about some people having some success in correcting the problem at least temporarily. But the fix is only a band-aid type repair. It involves partially disassembling the panel and placing a cushion over the affected tab bond. Try searching for some Sony LCD posts by OnlyTono. Perhaps some other members here have some other ideas, resources, or links.


Start here: http://www.avsforum.com/avs-vb/showthread.php?t=1173106

Found the info! Thanks!

Thread I read though don't mention what material they used for the cushion.


Any suggestions? I'm concerned with the heat melting what ever material I use.
 

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I use the soft pliable material that I find on heat-sinks. Not sure what it is called. LG sometimes calls it "chocolate". I'm sure there are numerous substances that would work. Time for someone with more experience in this procedure to chime in.

Good luck Majoram!
 

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Quote:
Originally Posted by EG3 /forum/post/20943708


I use the soft pliable material that I find on heat-sinks. Not sure what it is called. LG sometimes calls it "chocolate". I'm sure there are numerous substances that would work. Time for someone with more experience in this procedure to chime in.

Good luck Majoram!

Ah thermal pads. Thanks again!
 
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