Corroded Wire Caused No Display In Samsung Monitor
MODEL AND MAKE: Samsung LS22CMZKF/XL LCD Monitor
COMPLAINT REPORTED: No display
HISTORY: This monitor belonged to the same person who brought a Numeric UPS for service, which was following a successful repair of his 40” Sony LCD TV. Unfortunately when he removed the VGA cable from the computer, he accidentally ripped off the female connector fixed in the Mother Board, because of which he had to bring the computer also to me for replacement of the connector. You can see the ripped off portion in a picture given.
TROUBLESHOOTING AND RECTIFICATION DONE: I opened the Monitor by pulling out the front frame from the top portion by lifting it upwards by fingers without applying much pressure on the screen. Then inserted the special tools on its sides to release the locks. After removing the front frame and the control buttons and Power LED which are fixed on it, removed the panel along with the metal box that contained the power supply and mother boards. There are no screws attached to the back cover. So, we have to just lift it out carefully. Then unscrewed the VGA connector fixed to the metal case, removed the screws of power supply and mother boards. Lifted the boards up just enough to remove all the connectors including the LVDS cable. I saw an added LCD driver board, which was found inserted under the power supply board, connected with wires, and attaching the connectors of both LCDs. The components on the inverter side of the Power Supply board were found removed or scraped off, indicating that some technician had replaced the original inverter supply by adding an external inverter board. Probably the inverter transformer would have become defective and replacement part might not have been available. Anyhow, after removing the metal case, I assembled the boards back, keeping it outside and powered on. When I measured the voltage on the power supply board that goes to the inverter, I found it to be 13V which matched with the marking. Then I checked the same at the external inverter board and found it to be reading around 3V. Now, if the inverter board was defective, the voltage should have dropped at the power supply itself, but that was not the case. 13V was present at the beginning of the wire but was showing around 3V at the other end. So, desoldered the wire from the inverter board and checked. Then it showed around 6V without any load; a clear indication of worn out wire. When I replaced this wire, the backlight got I then replaced another wire which also showed corrosion. This is because of poor quality of wires that use iron strands instead of copper. Evidently it is made in China, which is very famous for making cheap electronic components.
There was a strange egg of some unknown insect that had got attached to the LVDS cable, which itself was in a bad shape. It was not that of cockroach as this was large. Anyhow, just cleaned up everything to the extent possible and applied Fevibond on some exposed areas of the LVDS cable, as a spare was not available due to complete lockdown.
After ensuring that the monitor was working well, by connecting the Test Generator, assembled it back and allowed it to run for a few hours. Now I have to take up replacement of the Female VGA connector in the Computer Mother Board.
Anyhow, mission accomplished and satisfaction did not fail to jump into its collection bag!
NOW TIME TO SEE THE RELATIVE PICTURES:
This article was prepared for you by Parasuraman Subramanian from India. He is 70 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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