Easy Repair With Only One Diode Shorted In LED Monitor
This e-wis LED Monitor came in for repair with the complaint of no power. The power LED was not lighted even the main ac was connected.
Once the cover was removed I could see the two circuit boards i.e; power and mainboard-see the photo below:
The main fuse was found to be good so I had to perform the on board voltage test to see if the power supply is producing any output voltages or not. The two output voltages that I had tested were 5 volt and 12 volt. There were no output voltage and this confirmed that the power supply indeed have problem.
I removed the power supply and checked on the two output diodes first. Surprisingly the first component (diode) that I had tested was shorted when checked with my digital multimeter.
This was the diode that was found to be shorted.
I checked further downstream to see if there is any other components found to be faulty but all checked to be good. Even all the secondary filter caps were checked to be good too. I concluded that there was only one output diode shorted and after the replacement of the diode look at the result below:
This article was prepared for you by Suranga Bandara who owns an Electronics shop in Anuradapura, Sri Lanka.
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Gregor
February 27, 2016 at 11:09 am
Nice ... thanks for the article!
Bhavit
November 1, 2022 at 4:38 am
Where to get this power supply board. Mine is burnt the same one. PW52067 model
beh
February 27, 2016 at 11:20 am
SURANGA : You told in article :The main fuse was found to be good
but in same board you found a big diode shorted how do you explain why the fuse did not act ? .and thanks, beh
Engr. Greatl
February 27, 2016 at 2:38 pm
Beh it is simple, the fuse was found to be OK and so also all the Components in the primary section was ok but if you look closely in the pictures above you will see that the shorted diode is on the secondary power supply which serves as a fast recovery diode,because it was bad it obstructed signals from going to the output stage which leads to no power.
beh
February 28, 2016 at 7:45 pm
Engr.Greatl
thanks for your answer .you mean this fuse is just functioning only for primary section of smps and not for all the psu and secondry am i right?
beh
Yogesh Panchal
February 27, 2016 at 2:49 pm
Suranga,
Congratulations! for this fix.
Ric fernandez
February 27, 2016 at 3:59 pm
Thanks for the article hey guys can you help me pinpoint the problem regarding pioneer stereo no power but the hdmi led blinking model vsx-323-k but the stby power for micom are ok.3.3v and 9v any hints guys thanks to all of you.
Parasuraman S
February 27, 2016 at 11:58 pm
Pl disconnect power supply to the amplifier board or section. In Pioneer Stereo, most of the times the mosfets that control 25V or similar gets shorted (for STK series amp ICs). So, isolate the power supply to this and check whether the LED is blinking. It is always better to search for free service manual for this model in google and study the circuitry. They might also give clue for the LED blinking in the service manual, under troubleshooting.
Graham Robinson
February 27, 2016 at 3:59 pm
Well done Suranga,i always enjoy reading your articles. Here in the UK we have too much of a throw away mentality when equipment fails which is why there are less & less people like you (and me) capable of repairing down to components. Also it's nice once in a while to get an 'easy' repair in for a change, i hope you made a good profit on this one 🙂
Regards
Graham
Robert Calk
February 27, 2016 at 7:20 pm
Good job, Suranga.
Parasuraman S
February 27, 2016 at 11:53 pm
One of the few 'gifts' or 'give aways' we, technicians get in our life! Anyhow, nice to see that the intuition developed out of your involvement and experience helped you catch the 'culprit' soon!
Akure, Olayinka
February 28, 2016 at 3:25 am
Thank u very much, i have been reading all your write -ups and am becoming very good in electronic repair.
Suranga Electronics Sri Lanka
February 28, 2016 at 4:35 pm
Hi my friends and Experts... Thanks so much your Feed back. Thanks All of you!!
jerry
February 28, 2016 at 7:41 pm
Nice one. Thanks.....
Mark
March 1, 2016 at 9:48 pm
Hey Suranga,
Thanks for the article. The diagnostic path makes sense and by isolating the circuits, the fault can be found.
Well done!
Arun
March 3, 2021 at 3:14 am
can you tell me please the diode number and its value...
because same fault found in my case... but when I replaced with new diode its shorted again...
Company has placed diode no. "SR520®" so I replaced with SR560 which shorted again.
So let me know that last digit is only symbol or its zero?
Humberto
March 4, 2016 at 10:52 pm
Another repair Suranga, congratulations
Chathura Kulathilaka
June 23, 2022 at 6:15 pm
it is super. thanks you lot