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Tampered Amplifier Set Repaired

By on May 4, 2019
amplifier set repair











how to fix amplifier

This Amplifier model Sonodyne SC1020 was brought to me by a regular customer with the complaint that it had on/off relay problems and it was given to a local technician, who could not solve it. Luckily, when a customer tells you openly that it was given elsewhere, we, technicians are always forewarned and look for unscrupulous tampering first. There indeed was such work on the PCB. The following pictures are self-explanatory not only for that, but also for very bad dry solders and a burnt resistor:

burnt resistor

burnt resistor

On checking the transistor, BC158B, legs of which were left unsoldered, the Peak Atlas showed:

peak atlas dca 55 tester

Replaced this transistor and also the resistor, and did a retouch of all the solder joints on the board and cleaned it thoroughly.

Look at the inside of the Amp and the finished PCB.

how to repair amplifier

how to fix and repair amplifier

Switched and the relay clicked after a few seconds delay, indicating that all was well in the Amp. Connected my USB player and checked the audio output. It was perfect!

For connecting the speaker outputs to EP type, I had made adapters, which I used in this Amp, as it was using Philips type.

fixing amplifier

amplifier fixed

I have made multiple connectors for various uses in the workshop, pictures of which, I shall share in one of my articles in the future.

So, the curtain fell on this service and got added to the satisfaction list, behind the screen!

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. Yogesh Panchal

    May 4, 2019 at 1:51 pm

    Excellent job!

  2. Albert van Bemmelen

    May 4, 2019 at 3:04 pm

    It is odd that your regular customer did not come immediately to you and went to the services of a local technician first. Sounds to me as a really bad decision made. And you probably had no problem with replacing the 2 burnt resistors with new correct values although they were hardly readable on their color code afterwards.

    • Robert Calk Jr.

      May 5, 2019 at 1:20 am

      Maybe he has Mr. Yong's e-book on finding the value of a burnt resistor? I am glad that I have it.

  3. Ghashaan

    May 4, 2019 at 6:14 pm

    Another good example that shows the importance of visual inspection in electronics repair. From the little that I learnt so far, it looks like that I can solve a variety of equipments just by using my senses. Before dipping my head into the field of electronics repair, I thought it's all about maths and logic. It's truly releiving to know that the game is much simpler in most of the cases. Thank you for the great articles. They are keeping me enlightened.

    • Parasuraman Subramanian

      May 4, 2019 at 11:05 pm

      You are welcome! Sharing the knowledge and experience that we gain only enhances it and it never gets drained. See how many experts turn out of Jestine Yong's internationally reputed institution! Is it not a great service to humanity?

      • Bhanu Prasad Swain

        April 8, 2020 at 2:40 pm

        Dear Sir,
        Can we get the circuit diagram of this Sonodyne Model SC1020. Now we need urgently. So request you to please help if its available at your end.
        Thank you.

  4. Robert Calk Jr.

    May 5, 2019 at 1:10 am

    Good job, Parasuraman!

  5. Paul

    May 5, 2019 at 7:12 pm

    Thank you very much for your technical knowledge

  6. Vikrant Kumar Srivastava

    July 27, 2020 at 9:55 pm

    Hi sir please find and send me the transistor number model sonodyne SC3100 or SC3070

    thank you sir

    • Mamta

      February 17, 2021 at 5:18 pm

      What is the transistor number of sonodyne 3100 model


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