Samsung LCD TV LE37R86BD Picture Quality Problem Repaired
This Samsung LCD screen TV set belongs to Marios, a close friend of mine. Last time I visited him he complained that the set reproduces the pictures with very bad quality. Here is his description:
“If you see the peoples’ faces, they look like zombies. There is something like black tear-drops in the edges of their eyes and similarly at their mouths. There are as well many white lines all around the picture and some times various surfaces look like being aluminized. I also see ghost-imaging, especially related to titles of previous scenes which do not disappear easily”…
The set’s front view is shown below.
The model number is that shown below.
As I put it in operation, in the beginning everything was normal. No problem at all. And this lasted around half an hour. Then, little by little the symptoms that Mario described to me started to appear…The picture became as shown below…
Marios asked me to take it with me and try to repair it and this what I did. First of all, before starting to troubleshoot it later on, I searched in the web to find any relevant information for this specific model, but I didn’t find anything. Then I decided to open it and troubleshoot it. After removing a thousand (!) screws of the back side, I finally saw its electronics. First I tried the “heat it-freeze it” method while seeing the problem on screen. No fruitful result whatsoever…
The “finger-as-thermometer” test did not reveal anything further. All I.Cs were operating normally, with no fever symptoms! Meanwhile I noticed that two electrolytic caps in the power supply section were bulged. I turned the power off and then I “scanned” it all around for high ESR caps, apart from those two. I spotted another one, an SMD type on the main board, which was marginal in ESR value and decided to replace them all. Below you can see the two 1000uF/35V caps already replaced, just above the transformer.
And here below you can see a part of the main board with two electrolytic caps, one at the left side and one at the right side of the smoothing coil, just below the big shielded area. I replaced the original (at the right side of the coil) which was the same type as the one at the left of the coil, with an ordinary one (non SMD type). Its rating was 1000uF/10V.
Then, I powered the unit again hope that I had eliminated all the problems of this set, but I was unlucky. The problem was still there… I thought to continue with the “heat it – freeze it” method at a time before the appearance of the problem. I tried it in the circuits of the main board with no positive results.
Next, I removed the shield of the T-Con board and tried to clean the contacts of the ribbon stripped conductors connecting this PCB with the display, because they were rusty enough. After the cleaning the two multi-pin connectors with cleaner spray and using a soft tooth-brush, the picture was improved but the problem was still present, appearing after some minutes of operation.
Then I tried the same method on this board as well, while the picture was good. Well, as soon as I sprayed on the tiny AS 15 – AF I.C the picture became almost negative. I repeated the same test several times just to be sure that there was problem with this set. After confirming this, I called the official service department here in Athens, to ask them about the availability and cost of either the defective chip or the T-Con board. The answer was negative for both of them.
After that I tried to find this I.C in the domestic market. No result either… I searched the web and found (through e-bay) a supplier from Hong Kong and ordered some pieces. When I received the chips, I removed the T-Con board from the chassis in order to replace the defective I.C. It’s the one surrounded with solder in all over its pins, as shown below.
Well, I tried very hardly to remove this chip using the methods I know so far, with no result. It was so hardly glued in its back side to the PCB that caused me big trouble. The classic method of heating all the pins with solder overflow on them and the soldering iron tip moving around them until the chip is lifted from its place, failed completely. The feeling I had was really frustrating.
Then I tried a method I saw in the “you tube”, heating the pins with the aid of that jig made from paper-clip and removing the chip by melting the solder and twisting the jig. You can see the jig below, but nevertheless this method failed as well. No result al all.
Having myself been now stagnant from any other brilliant ideas, I decided to cut off all the IC’s pins using a sharp cutter. Finally this was the only effective method to remove it and still, with all its pins cut, this IC was so hardly glued that I used (gently) a small screw driver in order to lift it!
After its removal and the following removal of its pins from their respective pads using the soldering iron tip, I saw four pads lifted. I used a magnifier lens to see some details on the PCB. Fortunately three of them were “blind” (not used) connections and only one had to be connected to the circuit. Now I was forced to run a “beeper”- continuity test to find the connecting point of the other end of the broken copper foil trace. After finding it, I bypassed it with a cable bridge and reinstalled the board on the chassis.
The critical moment had already come…I powered the unit…and you can see the result below.
Below you can see the defective chip (or rather what’s left from it)!
The proper function of the set was restored!
This article was prepared for you by Paris Azis from Athens-Greece. He is 59 years old and has more than 30 years’ experience in electronics repairs, both in consumer and industrial electronics. He started as a hobbyist at the age of 12 years and ended his professional carrier as a senior electronics technician. He has been a specialist in the entire range of consumer electronics repairs (: valve radio and BW TV receivers, transistorized color CRT TV, audio amps, reel and cassette tape recorders, telephone answering and telefax devices, electric irons, MW cooking devices e.t.c) working in his early stages at the official service departments of National-Panasonic first and JVC afterwards, at their premises in Athens.
Then he joined the telecoms industry, working for 20 years as field supporting technician in the sector of DMRs (: Digital Microwave Radio transmission stations), ending his carrier with this subject. Now he is a hobbyist again!
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