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AC Voltage Protector Repaired

By on October 25, 2014











electronic protector

AC Electronic protector can be found in all around the world. This is a local brand machine and the functions of electronic protector are:

1-    Within the first 5 minute after plugin the AC cord of the machine to the AC outlet, there was no output voltages and the Red power LED will be On.

2-    During this time the circuit starts to check the incoming AC voltage and the range should not lower than 185V and not more than 245V.

electronic protectors

3-    If the AC voltage is within range the Green power LED will turn ON and there will be output voltage.

4-    This checking is continuous and in any seconds if the incoming voltage is too high or too low than the rated specification, then it will cut off the output voltage thus protecting the electrical devices connected to it.

This device is most useful when an area electricity is cut off and suddenly it was restored or if there is a frequent Off and On due to instability of the AC source . The initial incoming surge AC voltage if not block it would cause serious problem to our home electrical/electronics devices.


The complaint of this protector was that it can’t function. This means it has input but no output voltage.


As you can see from the photo  above there are not many components installed   on the circuit board so I had decided to repair it by using the Eliminating method.

With this method one must check all the components one by one till you find the bad component. The tools that I used in this test were the analogue and digital multimeter, ESR METER and digital capacitance meter.

In the above circuit, I have tested all the resistors, diodes, caps as well as relay and all of them passed the test successfully except one resistor and the value was 1 Mega Ohm ( Brown, Black Green and Gold). It reads 1.623 M Ohm. After the replacement with a new resistor the protector refuses to work. For your information the only component that I did not test was the Op-amp 14 pins DBL324 IC. I believe this IC is bad also and need replacement since a new resistor did not restore the unit. Since I can’t find one in my spare parts compartment I looked up to Google for an answer. From the information I had gathered this IC part number is more or less the same function as LM324N (National brand).

After the replacement was done I turned the machine On and it worked but not for long. After sometimes the IC failed again. I decided to replace it with original part number and guess what? It worked like a charm!



This article was prepared for you by Mr Beh, one of our ‘Master Authors’ from Iran.

Please give a support by clicking  on the social buttons below. Your feedback on the post is welcome. Please leave it in the comments.

By the way if you have any good repair article that you want me to publish in this blog please do contact me HERE.





  1. Yogesh Panchal

    October 25, 2014 at 12:24 pm

    COngratulation Beh.

    • beh

      October 25, 2014 at 10:31 pm

      YOGESH: you are welcome.

  2. biruk aweke

    October 25, 2014 at 1:09 pm

    Mr. Beh very nice and have a nice day.

    • beh

      October 25, 2014 at 10:33 pm

      BIRUK: thanks for comment.

  3. Osman Alsinnary

    October 25, 2014 at 1:31 pm

    Good Job & Nice Article Beh ...

    • beh

      October 25, 2014 at 10:34 pm

      OSMAN: thanks dear

  4. moshe

    October 25, 2014 at 1:58 pm

    Great replacement parts are sometimes close but not close enough!

    • beh

      October 25, 2014 at 10:36 pm

      HI MOSHE
      yes .some time replacement must be also original part& you are most welcome

  5. Waleed rishmawi

    October 25, 2014 at 2:08 pm

    Good job. I really enjoyed that article. It is strange that the IC replacement did not last long. I guess amp rating is less.

    • beh

      October 25, 2014 at 10:39 pm

      WALEED: you are welcome .i am happy you like this report yes could be.

    • beh

      October 26, 2014 at 7:38 pm

      Waleed:Robert discovered that two ic s are not exactly the same that is why may be? the reason

  6. Mark

    October 25, 2014 at 3:35 pm

    Hey Beh,

    I have had similar problems to what you experienced. What is given as an equivalent is sometimes not quite right and the unit fails in time.
    Thanks for the article.

    • beh

      October 25, 2014 at 10:44 pm

      Hi Mark
      yes sometime we should replace the bad part with original parts . and you are welcome

  7. Erik Blankers

    October 25, 2014 at 8:25 pm

    Hello Beh,
    Do you know where to buy this protektor ?
    Or have you a elektrical drawing/ scheme so i can build it my self.

    Very interesting product because all the other commercial protektors are only overprotecting.

    erik from the

    • beh

      October 26, 2014 at 1:06 pm

      ERIK: this device plus postage fee will cost you 30 USD.

  8. beh

    October 25, 2014 at 10:51 pm

    ERIK:as i told in report this is a local brand . and i do not have diagram of this protector . if you want to buy this you have to buy it from IRAN TEHRAN .yes this device has delay line for first start up for 5 minute if you want to buy this via post this would be very costly for you .

  9. Patrick Yun

    October 25, 2014 at 11:16 pm

    Hello, Mr. Beh. Thank you for sharing your skill.
    You said you checked all components of circuit board, right? So, did you take all components out from circuit board when you test them?
    Thank you.

    • beh

      October 26, 2014 at 7:08 pm

      Hi Patrick
      the really, big plastic cap , 1 M resistor are tested out of circuit other ones in the circuit is tested

  10. John Broste

    October 26, 2014 at 12:44 am

    If one look at the equivalent schematic of the LM324 and the DBL324.
    You will discover major difference in the internal circuit of the IC.

    • beh

      October 26, 2014 at 7:11 pm

      John : yes that is why LM 324 could not stand for a long time and failed.

  11. Rudi Wijaya

    October 26, 2014 at 2:13 am

    Nice repair Mr Beh ! Thanks for the article !

    • beh

      October 26, 2014 at 7:12 pm

      Rudi: you are welcome .

  12. Michael

    October 26, 2014 at 2:39 am

    I wish there was a faster and LESS Expensive way to check this Type of IC(the cost of equipment is a lot of money for me as a Hobby to help people. I don't charge people to fix.),All these post to show "HOW TO" are very helpful to me and I am sure to a lot of other's Thanks' to all of you that for Sharing your KNOWLEDGE.

    • beh

      October 26, 2014 at 7:22 pm

      Michael: yes i know and i am sure that there is such ic tester to check this ic but i do not have such equipment the only way that was left for me was elimination method as you see this method works and no need for very expensive equipment i think this kind of ic tester is about 3000-4000 usd. you are welcome

    • John Broste

      October 27, 2014 at 10:36 pm

      ABI Electronics in England,
      have different IC testers for In/Out of circuit testing.

      They have models for Analog and Digital IC test`s,
      with a search function for locating unmarked IC.

      It saves me hours of fault finding.

  13. imam

    October 26, 2014 at 7:18 am

    great, your article

    • beh

      October 26, 2014 at 7:23 pm

      IMAM: Your welcome

  14. Austin

    October 26, 2014 at 1:57 pm

    nice article,please how do you check the enquivalent number of that ic in internet?

    • beh

      October 26, 2014 at 7:33 pm

      AUSTINE: you have to ask from google in this way: LM324N DATA when you received this data you have to save it. then ask about the DBL324 after that you can compare these two data to reach to a result

  15. Robert

    October 26, 2014 at 2:58 pm

    Good job Beh. Thanks for sharing with us. After looking at the data-sheets of the op-amps, I'm not surprised that the LM324N would not work. The op-amps internal structures are different, and the LM324N has 8 fewer transistors and 1 more diode than the DBL324.

  16. beh

    October 26, 2014 at 7:28 pm

    ROBERT : you are welcome .but i will thankful of you if you tell me how this op -amp ic is doing all these jobs ?and how test the voltages and so and so .all other parts in the circuit are only passive components!

    • Robert

      October 27, 2014 at 3:16 pm

      Hi Beh,
      The IC is just a quad op-amp - it has 4 separate op-amps in it. The outputs of the op-amps are pins 1, 7, 8, & 14. Pin 4 is Vcc and 11 is ground. The other pins are the inverting & non-inverting inputs. The IC LM324N has the same pinouts as DBL324, but they are different inside. You can go to and download the datasheets for free.

      • beh

        October 27, 2014 at 9:31 pm

        MY FRIEND ROBERT: thank you so much of all infos but still i do not know how this digital op-amp ic verify the high and low voltages?

        • Robert

          October 28, 2014 at 4:20 am

          lol! Yes you do. You were probably learning electronics before I was born.

          • beh

            October 28, 2014 at 12:08 pm

            no i do not know how this machine works! and i am just 35 years old .

        • Robert

          October 29, 2014 at 6:11 am

          All anyone has to do is google op-amps...

  17. Imraz

    October 27, 2014 at 5:27 am

    Thanks for this nice article Mr. Beh. great repairing

  18. beh

    October 27, 2014 at 12:12 pm

    IMRAZ: you are most welcome.

  19. Humberto

    October 27, 2014 at 8:55 pm

    Hi beh, great article. Explanations were good. Have a good day

  20. Andre Gopee

    October 27, 2014 at 9:29 pm

    Hi Beh, Great article.... You can test these Op-Amps to know if they are good or not. I will do an article on testing Op-amps so you guys can test it successfully.

    • beh

      October 27, 2014 at 11:43 pm

      Hi Andre
      you are welcome . we will be thankful of you if you prepare such article for us .by the way i am going to make the PART -2 of above article and will come soon .

    • Robert

      October 28, 2014 at 4:24 am

      That's a great idea Andre. I can't wait to read your article. I just use my DMM and check the voltages.

  21. beh

    October 27, 2014 at 9:32 pm

    HI HUMBERTO: you are welcome.

  22. Gurpreet

    August 6, 2015 at 5:53 pm


    Nice job and thanks for sharing this with us.


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