Servicing Dell LCD Monitor
This LCD Monitor was brought to me with the complaint that it was dead (Hospital Service Workshop). On visual inspection itself I could find out that the AC Female Connector had collected fungus and stuck. With a lot of difficulty, I removed it and saw that one of the pins on the monitor side had come off along with that. After opening the set, I removed the Male pin from the board, melting the plastic and forcing it out.
I did not de-solder the pins as an exact replacement was not available and we have to fit a different connector in its place using the old pins.
Very carefully soldered the new connector, which had straight pins instead of the bend and placed perfectly in its position.
Removed the mother board and connected a series bulb and switched it on. Still Dead. Disconnected, discharged the tank capacitor and checked for ESR of capacitors and any other failures. Checked primary of SMPS transformer with Blue Ring Tester and found it to be ok. Brought the board home and checked whether switching was taking place, using the oscilloscope (As per guidelines provided by Jestine Yong in his world famous book SMPS Repair). There was no oscillation. On further checking, I suspected that one diode near the PWM IC is not proper. Replaced it with IN4148. Since I had no SMD Diode, I soldered the regular one in its place.
Connected power through series bulb and got the 5V.
Took the board back to Hospital and fit it in.
Since I was going out of station that day, I was in a great hurry. So, after fitting and checking that everything was alright, I gave it to the department for fitting it back. Subsequently learnt that it was working well.
Sorry, I could not take snaps of the monitor in working condition. But believe me, it is working! (LOL). Another satisfactory work added to my list.
This article was prepared for you by Parasuraman Subramanian from India. He is 68 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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You may check on his previous repair article below:
https://jestineyong.com/servicing-toshiba-cd-usb-radio-cassette-recorder/
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Albert van Bemmelen
March 29, 2018 at 11:38 pm
Good job Parasuraman. I understand that the bad smd diode you replaced also was a 1n4148?
Parasuraman S
March 30, 2018 at 9:08 am
Yes!
Tyrone.
March 30, 2018 at 4:50 am
Very good Parasuraman
Johnson Thottan
March 30, 2018 at 8:58 am
Very good Parasuraman. At this age you are still doing and studying. Wonderful.
Robert Calk
March 30, 2018 at 10:02 am
Good job, Parasuraman. I believe you.
Yogesh Panchal
April 6, 2018 at 3:41 pm
Good Job! Sir