Dead Compo Board In DELL Computer Monitor Model D1918H Restored
This monitor belonged to the hospital where I worked and was brought to me in dead condition. I pried open the front panel, and removed the back cover to expose the metal case that housed the boards. Surprisingly, I found a single compo board used instead of the usual separate Power Supply Board and Mother Board.
Let us have a look at it:
The backlight connector could not be removed from the board, but it could be from the LED side. There was no way of removing the LVDS cable from the board without removing the screws and taking out the PCB. This might strain the cable unless we are careful and gentle in handling it.
The keyboard PCB connector also could not be removed without taking out the board! Strange are the ways of innovations implemented making service more and more difficult for technicians! Here you can have closer looks of the PCB:
After removing the board, I applied power through a series bulb and found AC reaching in and B+ primary voltage building up to 318V across the tank capacitor. So, the primary PS section was ok. Since I am accustomed to finding diodes short in the secondary, I straightaway checked it (of-course after disconnecting the power and waiting for selfdischarge of the tank capacitor). I found one of the parallel diodes short in yet another strangely paired rectifier diodes.
One was SB560 (5A 60V) while another was SB3150 (3A 150V). The SB3150 was the one which was found short!
Probably a way to blow this diode in case of uncontrolled power surge, suspending power supply and saving damage to other parts of the board! I replaced the diodes and applied power to find the output of 16.95V with LED lighting up blue and turning to amber because of lack of signal input (16.76V):
I reassembled the board back into its case, reconnected the backlight and applied signal to find the monitor working very well. Then put back the cases, having accomplished the mission, and satisfaction finding its target:
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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You may check on his previous article on Rare Case Of SMPS Transformer Primary Open Found In SONY DVD Player Model DVP-SR200P
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Waleed Rishmawi
February 15, 2025 at 11:54 am
Good job on the repair my friend. These are Schottky diodes and I am happy to see that you replaced both. Thanks for sharing and have a blessed day
Parasuraman S
February 15, 2025 at 2:37 pm
Thanks for the comments, dear friend!
Yogesh Panchal
February 15, 2025 at 3:21 pm
Good Job! Sir
Parasuraman S
February 15, 2025 at 7:29 pm
Many thanks!
Albert van Bemmelen
February 15, 2025 at 7:31 pm
Another quickly diagnosed and fixed monitor repair! Although disassembling and afterwards putting the monitor parts together again no doubt took most of your time.
Parasuraman S
February 15, 2025 at 10:01 pm
Absolutely! The opening of the closely snapped cover is the biggest problem ever. We need to be very patient, prying the sides very carefully without causing major damage! Many thanks for your keen observations and comments as usual, dear Albert!
Imoudu
February 16, 2025 at 4:15 am
Dear,you got me confused,is it'compo' or combo or slip of fingers on keyboard LOL.Well thanks for sharing.
Parasuraman S
February 16, 2025 at 9:59 am
It is combo board only. Looks like the spelling mistake got overlooked. Thanks for pointint out!
Mark J
February 16, 2025 at 4:52 am
Parasuraman great job on the repair.
Parasuraman S
February 16, 2025 at 10:00 am
Thanks, dear Mark!
Tito Kanshulu
February 18, 2025 at 8:52 pm
Good job Sir, and well articulated article
Parasuraman S
February 21, 2025 at 4:17 pm
Many thanks, dear Tito Kanshulu!
Derek Nathaniel
March 5, 2025 at 1:00 am
Good job I understand it is difficult to open the circuit boards but it requires patience .... the diodes should always be checked and sometimes the diodes are leaky i had a leaky diode problem with a JVC colour TV in the matrix stage it was tricky to detect but faulty part has to be replace to get the set working.