Problem In Optoisolator IC
The most common fault for an Optoisolator IC is the short circuit between the collector and the emitter pin and you can test it by using an analog meter set to X 10 K ohm and it should not show two readings. If there are two readings then it is either consider shorted or leaky. The LED diode inside the Optoisolator IC rarely have problem and you can test it using analog meter set to X 1 Ohm and it should have one reading.
In power supply, if the Optoisolator have problem it will cause many different types of symptom like no power, low power or even power shutdown. Since this IC is not difficult to test, i suggest that if you come across problem with the power supply with the symptoms that i have mention above, you may check on the Optoisolator IC first. What about Optoisolator IC that breakdown when under load? Yes in my repairing career i do came across Optoisolator IC that breaks down when under full operating voltage but it was rare too. If you have test all the components in the power supply section and still could not find out the fault, i guess there is no harm in replacing the IC and retest it again. Who knows the power supply may come back to life again.
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Waleed
July 1, 2009 at 8:00 am
thanks for the tip. i have this LG DVD/vcr compo machine that goes to stand by mode few seconds after I turn on the mahine. I checked all the power supply and bud not check this one, I will give it a try and check it out. I will keep you posted. thanks again for the tip.
Waleed
July 1, 2009 at 2:18 pm
can the testing be done with a digital fluke meter? just by using the diode setting and the transitor setting. please let me know
admin
July 1, 2009 at 7:03 pm
Hi Waleed,
Yes you can but not accurate as compare to use an analog meter.
Jestine
OSCAR
August 23, 2018 at 2:08 am
sir jestine,a crt tv universal boad no output voltage at the secondary pins of chopper transformer but primary side all component test good and am getting 270vdc at collector of chopper transistor.please help me sir
Jestine Yong
August 26, 2018 at 8:04 pm
Hi Oscar,
Have you checked all the components in the power primary side? Have you checked if the secondary output voltages good? Have you replaced the power ic and retest?
Jestine
admin
July 1, 2009 at 7:04 pm
HI Waleed,
Hope you will find the fault.
Jestine
beh
July 1, 2009 at 11:34 pm
hello jestine
i have seen optisolator with six leges if you tell me what are those two extra
leg going to do? with optoisolators i will be more thankful
tkx
beh
admin
July 2, 2009 at 11:26 pm
Hi beh,
The extra two legs, one is no connection which located at the LED side and the other one is Base pin.Please click on the link below:
http://www.electronicrepairguide.com/optocoupler.jpg
Jestine
ravichandran
July 9, 2009 at 7:51 am
thanks for the tip. i have this smps that goes to stand by mode few seconds after I turn on the mahine. I checked all the power supply and bud not check this one, I will give it a try and check it out. I will keep you posted. thanks again for the tip.
lokesh mohapatra
November 17, 2009 at 4:42 am
Thank you very much sir.We have done a project on remote fan regulator where opto isolator is used.your tips helped us and now our project is ready.
admin
November 17, 2009 at 7:18 am
Hi Lokesh,
You are welcome!
Jestine
bill
March 3, 2010 at 12:03 am
WHAT IS THE MOST COMMON CAUSE OF OPTOISOLATOR FAILURE?
Altaf
March 5, 2010 at 7:40 am
i have an airplus Xtreme G wireless Router. its some astonish problem when i on this device it works properly but some of time it hangs and some of time not hangs couple of dose. so please tell me Is it power supplu problem or the problem or ruoghter board. and please tell me its solution
thanks jestine
ur student Altaf Hussain from Pakistan
admin
March 5, 2010 at 8:59 am
Hi Altaf,
The best way to confirm is to make sure the power supply produce good output. Check for dry joints and all e-caps with esr meter.
Jestine
Daniel F
September 27, 2010 at 1:04 pm
I recently came accross a Toshiba LCD Television with a shutdown problem. The complicated circuit used 4 NEC 2561A optoisolators.
As you suggested I found the datasheet first to make sure it never used a diac internally, these use LEDs.
I tested all 4 optoisolators using your method above with an anologue meter and none of them gave a reading when I tested on the x10 kohm scale between the emitter and collector. In other words, no reading either way.
I then tested the same pins using an expensive fluke Digital Meter and it read 0L meaning 'open circuit' or reading off scale.
Here's the datasheet link for anyone interested.
http://www.datasheets.org.uk/pdf-datasheets/Datasheets-22/DSA-434552.html
admin
September 28, 2010 at 9:58 pm
HI Daniel,
Not necessary the optoisolator have problem because in certain part number, the internal resistance is very high you will not get any reading. You can connect two analog meter in series like a battery and set to x 10 k ohm and retest the ic again. If it still does not show any reading, most probably the internal transistor already got problem.
Jestine
Gerald Giasson
December 9, 2010 at 7:40 pm
Hi Jestin,
I am trying to purchase this part number (NEC2561DE351) from Digikey . However, the above part number does not quit fit the Digikey part list and in addition there are various specs related to this part. Which Digikey part would best fit the above part number? The above part came from a power supply. The opto is marginal and causing the power supply to go into an over voltage shut down. FYI. Thanks.
Gerald.
admin
December 12, 2010 at 10:35 am
HI Gerald,
I could not find any info in Digikey too. Try this link:
http://www.utsource.net/ic-datasheet/NEC2561-441774.html
Jestine
Gerald
December 18, 2010 at 6:48 pm
Jestine,
Thank you :).
Gerald.
wycliff
December 23, 2010 at 4:30 am
thanks waleed but i've got this dvd power supply and the fuse blew up and another IC(VIper22A)also blew could it be this optoisolator causing the problem. thanx again
Amir Mukhtar
February 21, 2012 at 8:25 am
Sir,
Thanks you
Nice guidance about opto isolator device.
Amir Mukhtar
leonard williams
May 22, 2012 at 7:35 pm
i would like a 42 inch lcd screen to buy any idea what the price is like
Jestine Yong
May 27, 2012 at 4:04 am
HI leonard,
Sorry I do not sell spare parts-try ebay.com
Jestine
Arcie Valeza
July 7, 2014 at 9:08 pm
Luciano,
Thanks for sharing your knowledge on repairing technique it's a great help...
Arcie Valeza
July 7, 2014 at 9:22 pm
Jestine Yong,
Thanks for a technical guide on OptoIsolator IC,how to test it and to check if it is functioning not all technician know about this,really thanks for sharing ur technical expertise..
Jestine Yong
July 7, 2014 at 9:38 pm
HI Archie,
The best is to direct replace Opto ic as some will breakdown when under load.
Jestine
Jared
February 1, 2017 at 9:30 pm
hi Mr. jestine
I just like your articles they really boost my spirit of repair
but is there way to modify this opt isolator ics incase there is no
close alternative to bring hope ?
Jestine Yong
February 2, 2017 at 11:24 am
Hi Jared,
It is all sealed thus it would be tough to modify one.
Optoisolator ICs are very common in the market and you should be able to find one online.
Jestine
mohammed
May 14, 2017 at 6:24 pm
I have switchable power supply it's funny normally 3_10
second
many of and sometimes don't run but restart cyrcle when I fixed it it run normally for 48 hours and then return to restarw cycle what's problem please help me
Jestine Yong
May 16, 2017 at 7:27 am
Hi Mohammed,
What have you checked and replaced?
Jestine
Mohammed
May 17, 2017 at 7:04 pm
Hi Mr Justine thanks you for replayed
In first time replaced small mosfet in the second circuit after that its run normally for 5 days and return to restart cycle while that happened short electricity caused by main cable and after test components find bigger mosfet shorted and replaced it with a irfp460 mosfet the original one is 24n60c3 after that the power is not run its restart after sound heard (tek) and after replaced the another mosfet (24n60c3 with irfp460 mosfet) and replaced the 3 optioisolator (sharp pc718) finally the power supply is run very easy and pc become fast and better but after a few days it's returned to restart after hearing voice (tek) from the power supply
Note : the voice(tek) hearing from power supply in the two cases (normally run and in restart cycle)
Jestine Yong
May 20, 2017 at 11:55 am
Hi Mohammed,
What kind of power supply you are repairing? How many output voltages it has? When you test the power supply did you connect to the mainboard?
Jestine
mohammed
May 21, 2017 at 2:01 am
I have pc power supply called cooler Master gx 750w when I tested all voltage is very good testing out of pc and when it's run out of pc it's run normally without any restaret the problem begin with start all loading of pc however some times run many hours without any problem but finally it must arrive to restart recycl behavior when I'm test another power supply on the same pc it's run without any problem
Jestine Yong
May 23, 2017 at 10:27 pm
Hi Mohammed,
Sorry I don't quite understand your meaning. Do you mean the power supply have problem when it is connected to the motherboard? When used another power supply connected to the motherboard have no problem?
Jestine
mohammed
May 24, 2017 at 4:14 pm
yes but the problem appear after many hours of use
Jestine Yong
May 25, 2017 at 9:40 pm
Hi Mohammed,
You may have to check for dry joints and use a coolant/freezer to find out the faults.
Jestine
Eric Rosano
November 16, 2017 at 3:21 pm
What if i short the emitter and collector, what will happen? because on my circuit when i shorted it the machine works. if it is not shorted it doesnt work.
Jestine Yong
November 16, 2017 at 9:12 pm
HI Eric,
It depends on circuit deign. Some power supply can start when you short the emitter and collector pins while other will cause no power, power blink and power shutdown problem.
Jestine
OSCAR
August 23, 2018 at 2:01 am
jestine sir i pray that God should give u healthy life and more years to serve us
jose armando sanchez valdez
January 19, 2018 at 5:33 am
hi justine yong..i need info of electronic tv trc..
Jestine Yong
January 22, 2018 at 10:11 am
Hi Jose,
Sorry I do not have info on TRC TV.
Jestine
Mulenga M
April 10, 2019 at 4:18 pm
Hi Justine,
I have lg home theater it turns on but doesn't work. You can change for instance from radio to CD but it fails to play no sound comes out even if its radio. Kindly help.
Rico Fernando
August 11, 2021 at 10:05 am
Hi Sir Jestine,
I encounter a problem on Dell Optiplex 390 power supply(H250AD-00) when i turn pc it shutdown after a minute. I tested another power PSU from another dell unit and it works fine.
I suspect the opto coupler (2 nos. 817 B and 2 nos. 817 C). Im wondering the suffix letter B and C whats the difference.
I can I just replace all 4 nos. with same 817 B or 817 C?
Please advice.
Thank you in advance.
Jestine Yong
August 13, 2021 at 11:37 am
Hi Rico,
The best is to use back the same version because different version have different gain. Being said that, some power supplies designs tends to be more sensitive. If you have replaced with the same version and the power supply still going to shutdown, at least now you know it has nothing to do with the opto isolator. But to some designs, they can take in any version. This means you have to test it out.
Jestine
Akililu
April 1, 2023 at 8:53 pm
Hi dear..
I my tv always optocoupler ic burn what is the reasons... One opcoupler ic not stay more than one day