Unexpected PC817 Opto IC Problem In Marchsal LCD TV
I received this LCD TV and claim of owner was when TV is not warm TV work as normal but after a while when TV getting warmer the picture start to blink. I tested it out and it was true.
First I thought that the problem must be from backlight, ccfl and/ or transformers inverter IC.
I checked them all and try to bring out the inverter IC from protection mode by grounding the sense pin of inverter IC to ground (when each of the ccfl or transformers are malfunctioning, the inverter IC is going into protection mode and the IC will turn off the voltages to backlights in order to stop more damages to the TV )
But after shorted the inverter IC to ground, the problem still exist! I replaced the driver IC and also all bad electrolytes like 24 volts, but still problem is not solved! By experience I knew that this could be from the bad intermittent ICs in power supply. The IC does not show any problem when is not warm but when getting warmer start to on/off.
But I found it by this old trick. When TV is not warm by getting close the tip of a hot soldering iron to each of the suspect ICs in power supply you can find the bad IC. This time I found intermittent bad IC it was Opto- coupler PC 817 in location 120 on the board when I getting close the hot tip of soldering iron to the IC and the picture start to blink.
By replacing the IC the TV return to normal service and one more electronic machine rescued.
This article was prepared for you by Mr Beh from Iran.
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Parasuraman S
October 12, 2018 at 10:15 am
Excellent! Very Good and useful tip too! Many thanks for sharing!
beh
October 13, 2018 at 8:46 pm
You are welcome.
Albert van Bemmelen
October 12, 2018 at 1:44 pm
Very nice trick you used to find the bad optocoupler Beh! Could also be a great way in finding power board problems by using the hot air of a hot air solder station?
beh
October 13, 2018 at 8:49 pm
Yes.also hot air has same result if we are looking for a component that when is getting hot shows the problem .
Robert Calk Jr.
October 13, 2018 at 6:52 am
Good job, Beh. I am glad that you found the culprit.
beh
October 13, 2018 at 8:50 pm
you are welcome. yes i am glad too.
beh
October 13, 2018 at 8:45 pm
HI
I want just tell that, with out very expensive tools just to know the methods electronic machines are repairable.
suranga Electronics
October 13, 2018 at 10:52 pm
Good Job ! Mr .Beh,
beh
October 14, 2018 at 11:10 am
You are most welcome .
Humberto
October 18, 2018 at 12:54 am
Wow! Beh, what a tip!. Thanks, I did not know anything about this. Thanks for sharing your experiencies.
beh
October 20, 2018 at 11:31 am
Hi Humberto
You are welcome . long time no news from you.yes by this technice i mean the hot tip of the soldering iron you may find any intermittent components that are sensitive to heat easily it is more precise than spraying or giving the heat by airgun . i am happy you find it useful.
cheers
behzad
Tito
October 26, 2018 at 8:37 pm
Good job Mr Beh, I the technique and the problem itself. this is quite interesting.
beh
October 30, 2018 at 8:13 pm
You are most welcome.
ryan
November 19, 2018 at 8:26 pm
you mean, the IC is not getting hot..so when you use Soldering Iron or Hot Air to make it warm, then it does it job...am i right?
very useful tip sir...Thank you sir