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Shorted Zener Diode Found In Voltage Stabilizer

By on December 5, 2018
voltage stabilizer repair










Voltage stabilizer fix

Voltage stabilizer repair

This is a voltage stabilizer that is in use for my Fridge. It had failed a couple of years back and that time, it was due to dry solder and I solved it and also replaced the electrolytic capacitors, since the ESRs were in the brim. My wife reported that the Fridge was not on and when I went and checked up, there was no output from the voltage stabilizer, even though there was input. I connected the Fridge directly and it was found working well. So brought the stabilizer for troubleshooting to my workshop.

As usual, the first job is external and internal cleaning, which I did quickly. Removed the PCB and found that there was no dry solder.

The stabilizer has two PCBs, one for its power supply, which housed the rectifier diodes, smoothing capacitor and 12V regulator IC. The next board was the buck/boost section, which had two relays. The relay was getting on when switched on, indicating that the primary power supply and the relay driver circuit was working alright.

Voltage stabilizer board repair

Voltage stabilizer board fix

Voltage stabilizer board fix and repair

how to repair voltage stabilizer

As you can see, the soldering was still intact.

I checked the semiconductors as well as the passive components and found only one 9.1V Zener leaky.

how to fix voltage stabilizer

Replaced it, gave power connection and checked the outputs. The LED was lit and the output was present.

how to fix and repair voltage stabilizer

Reassembled the unit and connected it to the Fridge and found it to be working perfectly well. My wife was happy that I could fix it so soon!

Another service added to my satisfaction list, with ‘double’ effect!

This article was prepared for you by Parasuraman Subramanian from India. He is 69 years old and has more than 30 years’ experience in handling antique equipment like Valve Radio, Amps, Reel Tape Recorders and currently studying latest tech-classes conducted by Kerala State Electronics Technicians’ Association. He has done graduation in BBA degree, private diploma in Radio Engineering and retired as MD of a USA company. Presently working as Consultant to Hospital and other institutions.

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You may check on his previous repair article below:




  1. ThandoSebeneleMavimbela

    December 5, 2018 at 10:13 pm

    tnx so much know l have learned something new

  2. Mason Sarles

    December 5, 2018 at 10:26 pm

    Thank you for sharing your repair. You have to love it when the repair is simple for a change.

    Thank you,

  3. Albert van Bemmelen

    December 6, 2018 at 12:54 am

    Interesting article. These kind of Voltage stabilizers are completely unknown in my country The Netherlands and surrounding countries. Most likely because they are not necessary here. I remember a similar device from an article written by our friend Humberto in Cuba.

  4. Waleed Rishmawi

    December 6, 2018 at 1:26 am

    Very good repair. Thanks for sharing

  5. Mihai

    December 6, 2018 at 2:01 am

    Good job Sir ! Thank's for sharing !


    December 6, 2018 at 2:51 am

    WELL DONE SIR (Parasuraman Subramanian)


    • Jestine Yong

      December 6, 2018 at 7:29 am

      Hi Angelo,
      I'm fine thanks.


    • Parasuraman S

      December 6, 2018 at 9:03 am

      Partially conducting to a path which it should not, is called 'leak.' A diode should not show low resistance on checking it in reverse order. But in this case, it was showing some resistance.

  7. beh

    December 6, 2018 at 12:17 pm

    Thanks for this repair report.

  8. Arunkant Pandit

    December 6, 2018 at 1:44 pm

    Dear Sir,
    All repair articles are very well explained by you. I am mechanical engineer but electronic repair is my hobby. I love all your articles.
    Thank you for sharing your hard work.

  9. Justice

    December 6, 2018 at 4:26 pm

    Good work Parasuraman, I have gained valuable knowledge with your article.

  10. Robert Calk Jr.

    December 7, 2018 at 1:22 am

    Good job, Parasuraman. Thanks for the article.

  11. Yogesh Panchal

    December 13, 2018 at 6:28 pm

    Good job! Sir,


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