What Everybody Ought To Know About Diagnosing LCD TV T-con Board With Gamma Distortion
One of my business associate asked me whether I can analyse the Samsung LCD TV for him. The model is LA32A330JLX which is in the store room for quite some time as it is very dusty when I received it. He said it too expensive to repair so he just kept it for sentimental reason. When I switched it on, the LCD display has incorrect colour, noisy disturbances at black level and poor contrast picture as shown below.
This type of defects normally caused by the main or the T-Con board . From the TV channel display, it is unlikely that the main board failure as it is impossible for the video processing circuits in the main board to display a problem on a specific area of the screen. Failure of the main board or video circuit normally appear noisy or distortion of colours across the whole screen.
Most likely the T-con board BN81-01868A (V315B1) is creating the problem. It cost around US$60 including postage which is on the high side considering the age of this model. Changing the T-con board can be a very fast & easy repair job but it is not cost effective or may not worthwhile to repair it. A better solution will be to try to trouble shoot the T-con board, since it may not be big problem as the major function i.e the timing controller is working fine or else the TV channel will not be able to display normal picture except with the problems mentioned earlier.
Just to be sure I check all the dc voltages and did not find any abnormality. In order to display the correct colour components, the grey scale or luminance video part has to be functioning normal just like in a CRT TV. I use the same analogy to trouble-shoot the incorrect colour picture problem. It would be easier to analyse & diagnose the problem with analogue signals rather than the digital signals which is much more complex. I have a ready DIY DVD grey scale pattern disk which I used it for CRT TV repair.
The analogue grey scale signal is apply to the LCD TV AV input and the screen display turned out to be abnormal grey scale image (see photo 1). From the abnormality and discoloration of the grey scale display, it is confirmed that the gamma correction or generator IC is no longer operating normal and not performing gamma correction with the original characteristic. The gamma correction IC could be damaged or deteriorated which resulted in tinted colour and noise generated being superimposed on the dark or grey level.
In the photo below is the abnormal grey scale being display with noise and tinted grey scale. Switched to a TV channel you will be able to judge how the grey scale can affect the picture quality (photo 1).
Photo 1: Effect of abnormal grey scale on a tv channel picture
Most LCD TV manufacturers do not provide schematics for T-con board and there are limited information on the internet. Spotting the gamma correction IC is not a problem as there are only a few IC’s on the board. The gamma correction or generator IC on this T-CON board is labelled as U6 with marking “ AS15-G” and it cost only around US$4.
Photo 2: T-con board V315B1-C01
After replacing the gamma generator IC (U6) the grey scale and TV channel picture is back to normal without noise or discoloration and with good contrast level (see photo 3).
This article was prepared for you by SK Wong from Malaysia and he graduated from London with a degree in Electronics and Electrical Engineering. He has more than 40 years of experience in the consumer product manufacturing. With the passion to repair electronic products from young , he has been doing it part time until now.
Currently, he can provide turnkey solutions for consumer products including services from idea or concept to design , prototyping , finished products (including electronic,mechanical and plastic parts) and manufacturing.
Please give a support by clicking on the social buttons below. Your feedback on the post is welcome. Please leave it in the comments.
P.S- If you enjoyed reading this, click here to subscribe to my blog (free subscription). That way, you’ll never miss a post. You can also forward this website link to your friends and colleagues-thanks!
Note: You can check his previous repair articles below:
https://www.jestineyong.com/how-to-detect-cracked-lcd-panel/
P.S.S- If you wish to learn more about how to repair LCD T-con board you can check out Kent’s ebook below:
(219)Dislikes
(1)
36 Comments
Leave a Reply
sudhir
February 9, 2016 at 6:12 pm
Good and very informative articular Mr Wong.
Thank you for your post
skwong
February 10, 2016 at 1:21 pm
thanks
Ernst
February 9, 2016 at 7:40 pm
Mr. Wong, that's one great job you've done. I still have to learn how to de-solder those chips
Robert Calk
February 9, 2016 at 11:58 pm
The problem for me isn't de-soldering the IC's, but the glue that is under them. It's hard to remove them without the glue ripping the top of the PCB with it.
skwong
February 10, 2016 at 1:13 pm
You need a hot de-soldering air gun to remove the smt IC. It is recommended to have a thermo-couple attached to the board near the IC to avoid excessive heat from damaging the copper track.
jose walter tenorio
February 9, 2016 at 10:41 pm
very Mr.Wong continue to reward us with excellent article like this , thank you.
Robert Calk
February 9, 2016 at 11:55 pm
Nice job, Mr. Wong. Thanks for sharing the repair with us.
skwong
February 10, 2016 at 1:20 pm
You are welcome. With the correct temperature, there should be any problem. For this IC there is no glue underneath . The real problem I encountered is solder underneath the IC which act as a heat sink and normally you will find it on the main board.
Robert Calk
February 10, 2016 at 10:37 pm
I had my re-work station as hot as it would get - I nearly burned the PCB up trying to remove the IC on a T-Con board. I think I need a BGA station or a hot plate or something so the PCB will be heated up on the backside so my hot-air will not have to work so hard. It was soldered underneath, but it seemed like it had glue also.
skwong
February 11, 2016 at 11:55 am
You can easily develop the skill from a few trial and errors. In my opinion and experience you do not need hot plate or air at the bottom of the pcb unless the IC is soldered underneath. My advise is to set the hot air to medium temperature of about 200 deg c for about 2 to 3 minutes to allow time for the heat to penetrate the IC.If you are living in a cold country, longer time is needed to heat up the board. Then set the rework station temperature setting to around 400 deg C for about a minute. Keep the air pressure low as well so that the heat is concentrated on the IC itself & not the surrounding.
If available use a thermometer with a thermo-couple wire attached close to the IC leads to monitor the temperature to avoid overheating. When the IC leads temperature rise to around 250~280 deg c the solder will melt. Good luck
Robert Calk
February 12, 2016 at 1:12 am
Yeah, I probably was trying to hurry to fast. I will try lowering the temp next time and see. Thanks.
Robert Calk
May 17, 2016 at 11:45 am
Thanks Mr. Wong. After heeding your advice I am having much better success! I was hoping to have a repair article on a Samsung LCD TV, but it turned out to have a bad panel. I still have problems with some IC's having adhesive underneath them. The adhesive is usually red in color and seems to be impervious to the heat.
Thanks for the help. Next time I'm going to try letting some acetone soak around the IC for awhile before I start de-soldering it with the hot-air in the hopes that it will soften the adhesive.
Edgar Colcol
May 29, 2020 at 9:42 pm
Hi! Let me ask you this. I opened the service menu of my samsung tv. My intension is to adjust the picture size that some parts of picture in the screen was hidden. I am looking for the vertical size or centering settings but i did not found. Then i accidentally press the adc that result to discolorations of the picture. The color temperature was changed. I do manually adjust the rgb bars but it didn't back to normal color. What will i do? Please help me.
Edgar Colcol
Philippines
thanku!
skwong
February 10, 2016 at 1:22 pm
thanks
tino choolun
February 10, 2016 at 12:46 am
salute Mr Wong
fantastic sir for sharing
good job
hope to hear you nice nice nice
tino Choolun
skwong
February 10, 2016 at 1:23 pm
thanks for yr appreciation
Yogesh Panchal
February 10, 2016 at 1:06 am
Good job! Sir,
Please keep sharing your experience.
skwong
February 10, 2016 at 1:23 pm
thanks
Mark
February 10, 2016 at 7:36 am
Hey SK,
Thanks for an informative and well written article. I have several TV's on my 'to do' list that I will be able to apply your techniques to.
beh
February 10, 2016 at 11:55 am
Hi Mr Wong
indeed your article is useful for me because i am repairing two LCD tv s SAMSUNG with same symptoms ,with these model numbers LA26R91B AND LA32R91B i would be very thankful of you if you give me any info about T-CON boards of these two tv s
beh
skwong
February 10, 2016 at 5:46 pm
Sorry, I do not have any information regarding yr model.You may check the T-con board marking , maybe other models could be using the same board.
skwong
February 10, 2016 at 1:29 pm
Hopefully this technique can help to resolve some of the problem. It may not solution to all the problems but at least it can narrow down the faults. Good Luck.
Suranga Electronics
February 10, 2016 at 2:03 pm
Thank Mr- SK Wong,
This one great job you have done and
Please keep sharing continue your experience.
Parasuraman S
February 11, 2016 at 9:20 pm
Fantastic! I learnt something new from you! Thanks for sharing your valuable experience to 'lifetime students' like us!
Selwin Matthew
February 15, 2016 at 4:15 am
Hi Mr Yong.I always learn from the info you provide.You have my gratitude.
Regards,
Selwin
Amir Mukhtar
February 22, 2016 at 1:43 pm
Thanks you Sir, SK Wong
I got great learned from your Article Above.
Keep Sharing to Learn Students and new commers.
Thanks you Again
Amir Mukhtar Ashrafi
Karachi. PK
LLOYD BOND
May 2, 2016 at 2:12 pm
VERY GOOD ARTICLE
Luis Abrenica
May 15, 2016 at 12:24 pm
SKwong,
Thanks for the repair info, and more power.
Luis
Tushar
May 21, 2016 at 12:49 am
Hi dear sir
I have toshiba LCD TV 32PS1E, tv is on normally & after 5 minutes display White line coming overall display.Could it be due to gamma controlled Ic?
Thank u
Chaminda J
June 21, 2016 at 7:08 pm
Thanks.
Jeffrey K.
December 1, 2016 at 11:40 am
Hello,
I have a LG 47LB6100-UG LED TV. Screen started to turn ON and OFF (Lite up and turn off). There is picture and sound. At time, thought it was the power supply unit. Changed 2 and only last for months each and started all over again. Now into my 3rd Power Supply Board, right off screen will lite up and goes off. What could be the solution? Please advice.
Boon Yong Tan
February 4, 2017 at 9:29 am
Hi Mr Wong, my Samsung UA60D6600's Tcon board is dead and I need to find out where can I make a purchase.
Kindly provide a contact or 2.
Thank you.
Sukhjinder singh
February 5, 2017 at 9:17 am
hlo sir
I have a lcd of samsung
LA32C450 there is sound ok but no image
I check backlight ok,LVDS cable ok,socket also very good no any dry
what I can do?
Abir
April 27, 2017 at 2:13 pm
Dear Mr. Wong,
I am interested to learn about LED tv circuitry. I have read your post and it's so informative.
Can you let me know how a T-con board works? Perhaps you can send me some documents for learning. I am also an electronics engineer.
Regards,
Abir.
albert
May 8, 2017 at 8:33 am
skwong
i have samsung plasma model PS43E490A1 the problem is when i turn it on theres power and and the channel sounds has it but no display at all. i'll make trouble shoot the power supply of VS is 221v but stated 208v and the VA is 58v wich normal,once the power circulate the VA and VS drop down the voltage. when i disconnect Y-buffer, Y sus. and remain x board but unplug the ribbon succetc going to the display connected to t-con. the VS and VA remain the voltage. but still no display. my t-con LED LIGHTS blinds 4-5 per second.i'll check also the display no damage, crack or ribbon burned.i hope sir u will give me information about this problem. thanks and more power...
al..
Daniel
February 27, 2020 at 4:24 pm
Thanks Mr.Wong for the lesson fantastic. ..long life but please we need your videos how main board works together with tcon