Bypass Surgery Done In SAMSUNG LED TV Model UA32T4450AKLXL
A known and regular technician who focuses on house old appliances brought the compo board of this Samsung TV stating that the fuse was blowing and he could not find out the reasons for it. Following is the picture of the board:
I removed all the glue coated on top of the high voltage switching section of the primary side.
Then found a 331K 1KV capacitor burst:
The real fault was this leaky capacitor which finally blew but remained obscure under the coating. I replaced this capacitor and the fuse of 3.15A, did a ring testing and combed the primary and secondary sides for any shorted components and did not find any. So applied power through a series bulb and found the board working very well with all the output voltages of 5V, 3.3V, 12V, 32V and 90V (LED backlight):
He collected the board from me and later reported that there was no display and only dark blue screen was seen, upon which I advised him to clean the LVDS cable and reinsert it. But he reported that still there was no display. Then I told him to bring the TV home. As all voltages were steady, I checked the voltages on the scaler board, pictures of which are shared below for those who might have interest:
The SM4186 was having the 12V, 3.3V and 1.8V at the appropriate pins indicating that the problem was in the panel side.
After consultation with my techie friends, I was advised to check the ohms between the four CKV lines:
From left to right, let us call them track 1, 2, 3 and 4. These tracks come out of the date lines through caps. I was asked to check resistance between 1 & 3 and 2 & 4. When I checked these, it was showing around 4.06 Meg. The next step was to compare the ohms between the same tracks that go from the left side of the COF also. When I checked these, they were in the order of 4.7 Meg Ohms range. I was then advised to cut the four tracks of the side that go to the panel and see. I took a sharp blade and used powerful lens to cut the four tracks that go to the panel as close to the COF as possible but leaving a thin margin to rejoin if necessary. Luckily, the display came on as soon as I cut the four tracks!
Then the next step was to join all the four tracks going to the panel that were cut. I managed to do that also. All these are easy to say, but took precious time on precision and intricacy involved. Following is the picture of the work done:
I forgot to mention an important point: The side to be selected for cutting is the one which showed lesser ohms. I left the TV on for several hours and noticed that it was working very well. I kept the TV with me for a morning trial too and found it was working very well.
The TV was a smart TV and the display turned out to be a big audio equipment, upon selecting music to be played from a USB. I was watching the latest developments in technology with awe and amusement. Anyhow, mission accomplished with satisfaction getting added to the bag. The technician collected the TV next day and paid my charges.
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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Waleed Rishmawi
July 26, 2025 at 7:12 pm
Good one. I never figured why they do the cutting and which ones to cut. I never attempted such repair and I thank you for sharing. Have a blessed day
Parasuraman S
July 27, 2025 at 7:51 am
I am glad it was helpful to you. Many thanks dear friend!
Albert van Bemmelen
July 27, 2025 at 12:12 am
As Waleed already mentioned I too wouldn't know what to do or what to cut in such events. But no doubt a good job done, although it doesn't explain what exactly in the circuit was changed! It would have been nice if a close-up of the circuit would have been shown that explained in detail what was fixed or changed with this positive effect.
Parasuraman S
July 27, 2025 at 7:53 am
The CKV lines to the panel were cut and joined together at the glass side. Many thanks for your expert and analytical comments, dear Albert!
Yogesh Panchal
July 27, 2025 at 1:21 am
Good fix! Sir,
DO CKV reading above 1MΩ consider to be short??
Parasuraman S
July 27, 2025 at 7:55 am
It should be very high for a normally working panel.
Mark J
July 27, 2025 at 2:52 am
Parasuraman great repair. Thank you for sharing.
Parasuraman S
July 27, 2025 at 7:55 am
Many thanks, dear Mark!
Imoudu O
July 27, 2025 at 4:31 am
To identify signal lines and ckv is a bit difficult for me,well good repair you have done,it seems to be cutting modifications rather than bypass though.
Parasuraman S
July 27, 2025 at 7:58 am
Cutting was done and bypass was by shorting the glass end tracks that went into the panel. Many thanks, dear Imoudu!
Muykit
July 28, 2025 at 6:15 am
Great ! Please dont bag it all share it with your techie friends who always stand by you.
I presume SM4186 is a gamma IC. Now this TV being a Samsung, the IC has among other principal functions; to monitor abnormal voltages and currents in that region of the TV set up. So once a short in the panel is sensed by SM4186, the IC, being a loyal servant, dutifuly triggers a safe mode that shuts down TV. SM4186 then sits and waits until the culprit CKV shorted lines are eliminated by the cut of a surgeons razor. Only then does TV functionality resumes using an extra path, so I think. Like in humans. a bad kidney is removed and one remains for someones continued survival.
Please techies lets share skills and views. No one amongst you is suggesting about the use of small jumper wires when rejoining ckv lines and joining all the lower pads of the linking capacitors so as to alternatively short them, or even just making it known that the word 'date' was supposed to be 'data'. I just love TV repair stuff.
Parasuraman S
July 28, 2025 at 9:24 am
Many thanks for your elaborate study and comments!
Andre Gopee
July 28, 2025 at 11:36 pm
Great Job... I too am alway wondering about CKV Lines.... How do you Identify which traces are CKV line... I have watch some videos on YouTube and saw wher they use a Short killer to repair shorted CKV lines. I just want to know how to identify them.
Parasuraman S
July 30, 2025 at 9:39 am
Those are lines that go through the sides of the COF normally. One single and next joined double again single. You may have to study videos and articles and practice it on panels. Guidance will be limited.
Thanks!