What Will Be The Symptom When VGH Is Missing In LED TV? – SAMSUNG UA24H4003AR
This TV was brought to me with the above complaint which was reported to have happened while watching the TV.
I opened the set and subjected it to thorough cleaning.
As there was display, everything in the Power Supply Board and Mother Board might be working very well. So, I checked the five essential voltages in the scaler board and got the readings as: VGL – (-) 7.92V, VDD – 3.25V, VCC – 12.70V, VGH – 0V, VAA – 12.70V. Evidently, the output of VGH was missing. The next step was checking for any shorting of capacitors on the scalar board or the inside the panel itself.
For that I cut the VGH out track from the IC and checked for any short and did not find any. So, the Voltage Booster IC CM501 itself was defective. As a genuine replacement was not available, I cut the output tracks of this IC and provided a small board like how I have done in a few cases before, by connecting wires to the spot on the scalar board and providing 3.3V from the mother board:
When I applied power, the TV was found working normally. After allowing it to run for several hours, I closed the cover and fit it back for delivery. I also run the TV for several more hours before asking the customer to come and pick-up.
Mission accomplished easily and satisfaction got collected as usual.
This article was prepared for you by Parasuraman Subramanian from India. He is 72 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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Tito Kanshulu
November 18, 2023 at 1:25 pm
Excellent repair Sir, though you didn't explain fully how you replaced the other scaler board since you didn't have the exact replacement
Parasuraman S
November 18, 2023 at 9:58 pm
No scalar board was replaced. It cannot be replaced without a need for bonding the COFs. What I did was removing the defective IC and providing all the booster voltages required for proper function of the panel from the external booster board. That board was fixed on a vacant place by double sided tape without causing any hindrance, like how I did in many TV repairs. Many thanks for your comments!
Waleed Rishmawi
November 18, 2023 at 3:21 pm
yes, sometimes we have to do that otherwise it will be sent back to the customer unrepaired due to the fact the parts are not found. I am having the same problem right now when it comes to parts. Due to the war situation in this country mail is not always allowed to come in creating an issue of lacking parts for repair. it is not the best situation for me but we do what we can to help out. thanks for sharing and have a blessed day my friend.
Parasuraman S
November 18, 2023 at 9:59 pm
Yes, dear you are right! Many thanks for your comments and inputs!
Albert van Bemmelen
November 18, 2023 at 3:26 pm
After so many tv repairs you probably immediately knew what the VGH voltage should have been and that it was the only issue here leading to a defective Voltage Booster IC CM501 probably a S13A1D33 chip according to the schematic that delivers 3.3V stua_pw to Tuner TU501 that came from AO6415/Q207 that provided 5.3V_PW to CM501 that was delivered by TPS5432/IC202. This way trying to follow your repair to also learn something. Apparently also another A3.3V_PW was provided by IC201 an AP1117D. All derived from the same B5.3V_PW voltage. But they still were called different A and B feeds. With this specific information that was missing I hope to follow these kind of TV repairs better.
Parasuraman S
November 18, 2023 at 10:07 pm
The CM501 mentioned here is a DC-to-DC converter and booster to provide appropriate voltages to the panel. Kindly see a datasheet here: https://www.alldatasheet.com/datasheet-pdf/pdf/1142234/CHIMEI/CM501.html
It is not a chip mentioned by you. This is a small 48 pin square chip, so small that we need to use microscope and special tools to remove it. It has a heat sink at the bottom and cannot be easily removed like others. Many thanks for your expert comments, observations and input!
Albert van Bemmelen
November 19, 2023 at 6:39 am
Understood dear Parasuraman. The chip I mentioned maybe came from the same tv model with a different chassis version? Document Troubleshooting page 3 of 16, from this service manual provided by Elektrotanya.com=>
https://elektrotanya.com/samsung_ua23h4003ar_chassis_u8ba.rar/download.html#dl
Cheers!
Parasuraman S
November 19, 2023 at 4:05 pm
I could not find any similarity to the chassis in the TV that I repaired. The service manual referred to by you is mentioning about a T-con board and it is not there in the TV that I repaired. Many thanks for the keen interest and efforts you have put in to dig out a schematic.
Albert van Bemmelen
November 20, 2023 at 12:24 am
Noticed that ElektroTanya had given me another wrong servicemanual Parasuraman. That was not the the one I had searched for which explains the differences. I guess you didn't have a matching servicemanual or circuit to go on either and was able to fix the tv wihout it anyway?
Parasuraman S
November 20, 2023 at 3:49 pm
No service manual or schematic was available. Many thanks!
Yogesh Panchal
November 20, 2023 at 10:57 pm
Good job!Sir,
Using variable Dc Bench Power supply is playing good roll for troubleshooting this type of problems where section using specific current.
Parasuraman S
November 22, 2023 at 11:59 pm
A good suggestion! Many thanks for your comments and suggestions!