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About Optoisolator IC In Power Section

By on June 27, 2009

power supply

If you are repairing a power supply that do not use optoisolator IC as a feedback that means if all the secondary output voltages read zero volt then i can say that the primary section have problem. It could be a dry joints, ciruit track broken, bad FET and power IC, leaky or shorted diode and transistor, cap that have high ESR or even an open circuit in resistor (start up resistor). However if the power supply use optoisolator IC then there is chances the secondary side components that corresponding to the optoisolator may have problem. If you concentrate only on the primary section, i can say you may not find out the culprit. A shorted optoisolator IC and TL431 IC could cause no power symptom (zero output voltage) and you may thought that it was the primary section fault.

Understanding the power supply design is one of the key to successful power supply repair.  Practice, practice and practice on different type of power supply repair (don’t just repair-you have to understand how it works) will make you better in solving  any type of power supply problems.

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18 Comments

  1. Songre

    December 19, 2010 at 5:40 pm

    Thanks Jestine, always a pleasure to read your comments. I am actually dealing with a problem like the above for weeks and this info open my mind quite a bit...appreciate it. We'll let you know if I solve this one...Cheers! Sharp 21S-FX10L No power, no standby light and on the Filter capacitor I get 69volts dc. no secondary voltages uses optoisolator # PC1213Y82.

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  2. admin

    December 20, 2010 at 6:30 am

    HI Songre,

    The filter cap dc voltage is too low. Try trace backward till the bridge rectifier stage.

    Jestine

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  3. Marulitua Hutabarat

    February 12, 2011 at 5:59 am

    Hi Jestine, glad to see you again.
    Did you ever repair InFocus Projector?
    I found it, no power, no standby light.
    I attempt to repair it, but I can't solve it.
    I just found the voltage at bridge rectifier stage 307 Volts.
    I ask you what is still go wrong? I found no broken fuses or mosfets.
    Thanks in advance.

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  4. admin

    February 12, 2011 at 10:54 pm

    HI Marulitua,

    No i do not repair focus projector but just like any electronic equipment troubleshooting the power supply is the same. Have you replace the power IC after you found no bad components in the power side? Sometimes a shorted component in the secondary side circuit could cause no power symptom.

    Jestine

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  5. Songre Osmenep

    August 25, 2011 at 4:34 am

    Jestine, I did repair this Tv it was the regulator in the power supply once I changed it works perfectly up till this day! Thanks my friend.

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  6. admin

    August 25, 2011 at 6:46 am

    HI Songre,

    Congratulation!

    Jestine

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  7. mike

    July 14, 2012 at 3:52 am

    it was a blessing getting your site and i appreciate the knowledge you impart on people who are interested in electronics especially myself.
    Keep it up Jestine

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    • Jestine Yong

      July 14, 2012 at 9:41 pm

      Hi Mike,

      You are welcome.

      Jestine

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  8. victor

    August 13, 2012 at 1:15 am

    Hi Jestine,
    I can't thank u enough for the hints I get from ur site. u've really transformed my repair skills. Really bad that i've not bought ur books. I do repairs for fun. Could pls tell me how to test the optoisolator in a SMPS(s). Thanks in advance.
    Victor, Lagos Nigeria

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    • Jestine Yong

      August 14, 2012 at 2:57 am

      Hi Victor,

      Try this link:

      https://www.jestineyong.com/testing-optoisolator-pc123/

      Jestine

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  9. TANA

    August 16, 2012 at 8:13 am

    Dear Jestine,
    You are surounded by a whole world of electronic.. And your notes and tips will have helped many readers. You are not only gifted but also very heplful and genrous.

    Likes(0)Dislikes(0)
    • Jestine Yong

      August 16, 2012 at 10:50 pm

      Hi Tana,

      YOU are welcome!

      Jestine

      Likes(0)Dislikes(0)
  10. Elaine

    August 26, 2012 at 5:19 pm

    My coby LCD tv get power through the power cord but not coming on. What is the problem

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    • Jestine Yong

      August 27, 2012 at 11:03 pm

      Hi Elaine,

      It could be the power supply have problem. You may need to check the internal fuse and start troubleshooting the primary side components. If you do not have experience on electronics repair I suggest that you send to your local electronics repair shop.

      Jestine

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  11. victor

    September 22, 2012 at 2:49 pm

    Thanks 2 u jestine for all ur effort  2 practice & compiled all dis 4 us & thanks 2 that kenya man 4 his breakthrough on opening of  adapter enclosures ; it works like magic

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    • Jestine Yong

      September 22, 2012 at 8:45 pm

      Hi Victor,
      You are welcome!

      Jestine

      Likes(0)Dislikes(1)
  12. alberto catindig

    June 5, 2015 at 6:11 pm

    Hi sir, i have a sony audio component, have -v but no +v secondary output . The display also tells protect e03. I need your advice and idea. Thanks

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    • Jestine Yong

      June 8, 2015 at 8:58 pm

      HI Alberto,

      Try trace the +v line and see if there is any bad component. It can be bad filter cap, bad diode and etc.

      Jestine

      Likes(1)Dislikes(0)

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