No Display Problem Solved By Cutting Tracks To Panel In DIANORA LED TV Model DN3201V
This TV belonged to my colleague in the hospital and was brought to me with the complaint that the display went off, while sound was heard, when watching the TV. I applied power and just gently tapped the screen and noticed that the backlight was present. After subjecting the TV for thorough cleaning, I brought it onto my desktop for investigating the reasons.
When I checked for the voltages in the scaler board such as VGL, VGH, AVDD, V-Com etc. these were absent, indicating either a failure of the control IC SM4186 or short in panel.
I got the above schematic from a techie-friend in the Whatsup group. A couple of friends told me to just cut four lines that got to the panel, near the COF, and sent me the following markings:
The advice given was to cut only 2 & 3 (the double tracks) starting from the left side. If picture appears, then only cut the 1 & 4. If the picture does not come, join them and cut the other side. In order for us to join, we need to first of all clean that area and make the copper track visible, by using fine (Number 100 – Zero Emery) sand paper. Then use a very sharp surgical blade and draw only just a thin line of the two tracks as close to the junction as possible (The dot side, not the COF side). Ensure enough pressure to cut the tracks taking care not to touch the adjacent lines. Keep the blade slightly in an angle while cutting so that the copper track just lifts up and stays there, instead of scraping it entirely. This will enable us to join with a little bit of solder in case of need, without spilling over to the adjacent tracks. This is a very intricate work and one needs to practice on any other defective board several times until get perfection.
I mentally spun the roulette wheel and chose to cut the right side 2 & 3 first. But picture did not come. So, joined it and cut the left 2 & 3. Then the picture came, upon which I cut 1 & 4 of that portion, without which several close lines may appear on the screen though not visible from a distance or in a camera snap. But the clarity of picture may get affected. Have a look at the operated areas:
You can see the result yourself here:
I have said before that I do not like to do these cheap tricks on a TV, but am forced to do so to prolong the life of the TV, when a customer so desires. Surprisingly, such bypassed TVs work for months or even years together afterwards! Any similarity you might find is such a bypass surgery done on human beings! Anyhow, I was thrilled to do such intricate jobs deriving satisfaction, which got a welcome entry by its predecessors promptly.
One interesting input given by one of the senior most technicians runs like this: Measure the resistance between these four lines. Do the same on the other side also. The measurement should first be between 1 & 2 or 3 & 4. Normally the shorts happen with adjacent tracks inside the panel due to carbon deposit formations. If the resistance is around 400 ohms and the other measures around 400.1 or more, the short is on the lower side. This again has to be experimented on several working TVs to gather enough data for comparison. There is no standard fixed and the resistance readings might vary. He mentioned 400 Ohms only just for reference purpose. It is a good advice, which I might try in my next chance, as another TV of same model and make with similar complaint is waiting to be repaired.
This article was prepared for you by Parasuraman Subramanian from India. He is 74 years old and has more than 30 years’ experience in handling antique equipment like Valve Radio, Amps, Reel Tape Recorders and currently studying latest tech-classes conducted by Kerala State Electronics Technicians’ Association. He has done graduation in BBA degree, private diploma in Radio Engineering and retired as MD of a USA company. Presently working as Consultant to Hospital and other institutions.
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Albert van Bemmelen
May 4, 2024 at 8:23 pm
Although very impressive, it is too complex and risky for my taste and I won't do such repair tasks. Also because I do not have any tech friends for this kind of support either!
Parasuraman S
May 4, 2024 at 10:13 pm
Many thanks for your expert comments and evaluation!
Anwar Yunas Shiekh
May 4, 2024 at 9:54 pm
I'm also not keen on cutting tracks to make things work.
Parasuraman S
May 5, 2024 at 10:11 am
But what to do? We cannot escape from such crude ways for the sake of survival in the field! Many thanks!
Yogesh Panchal
May 5, 2024 at 12:54 am
Good Job! Sir,
Your way of working inspires us to tackle the difficult task. yes techie Friends play major roll in our success.
Parasuraman S
May 5, 2024 at 10:12 am
Many thanks for your encouraging comments!
Waleed Rishmawi
May 5, 2024 at 4:26 pm
I have not done this kind of repair before because I was not provided with the chance to do it. Thanks for sharing and have a blessed day
Parasuraman S
May 5, 2024 at 9:41 pm
But the kind of repair work you get is multifarious and branches to many!
Rodrick Makanga
May 8, 2024 at 11:15 pm
Manufacturers like long cuts while the shortcut can also work! Thanks
Parasuraman S
May 10, 2024 at 5:24 pm
Many thanks for your humourous but factual comment!