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Voltage Surge Blew Transformer Of BPL M9903-H Two Converted To Three-In-One

By on July 15, 2023
Voltage Surge Blew Transformer Of BPL M9903-H Two Converted To Three-In-One







I request you to read my previous article, if you want to know the history of the set, as it was converted to three-in-one:

Modifying BPL M9903-Two-In-One To House USB Unit In Place Of Tape | Electronics Repair And Technology News (

The set was given back on 1st April, 2019 but revisited on 22nd of March, 2023 with the complaint that it was dead. On checking I found that the primary of the Transformer was open. The customer reported that there was a voltage surge in their house and it happened only after that.

I picked up a better rated 9-0-9 Transformer from my stock and did the preliminary wiring of Two DC supplies (one for Main Unit and one for the USB device). I used a 7808 and used an IN4007 diode in the output to drop half volt as the set worked on 7.5V and 7805 for the USB.

I housed the transformer in its original place and provided an automobile type fuse holder with a 1A fuse in the primary and placed it in the battery compartment.

transformer blew

The set worked perfectly fine and was tested for several hours in various modes before giving delivery to the customer.

fixing three in one player

Mission accomplished and satisfaction got collected.

(Unfortunately I forgot to take a snap of the old TX).


This article was prepared for you by Parasuraman Subramanian from India. He is 72 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 article on Swing Motor Shaft Exchanged And Modified In A Nameless Bladeless Fan




  1. Albert van Bemmelen

    July 15, 2023 at 1:19 pm

    Apparently it is quite common to read about equipment destroying AC voltage surges in houses in other countries. They are not that frequent in my country. But fires and power line problems do exist. Mainly because of the daily growing need for new distribution capacity that has its many limits.

    • Parasuraman S

      July 15, 2023 at 9:10 pm

      Very true! Many thanks!

    • Henrique J. G. Ulbrich

      July 17, 2023 at 12:36 am

      Albert, perhaps you do not observe these problems due to some differences. Surges are mainly observed in electrical grids based on poles (outdoor distribution). Perhaps in your country, the utility uses mostly underground distribution. Also, some countries have more incidence than others, like my country. Brazil is the country with the majority of lightning bolt incidences in the world: about 70 million a year. Ultimately, lightning bolts are more frequent in rural areas.

      • Parasuraman S

        July 17, 2023 at 9:08 am

        Yes, I agree with you! Many thanks for your comments!

  2. Yogesh Panchal

    July 15, 2023 at 5:01 pm

    Good Fix! Sir,
    I think it can be further modified on 5v mobile Charger if Transformer is not available.

    • Parasuraman S

      July 15, 2023 at 9:10 pm

      Many thanks!

  3. Arunkant L Pandit

    July 15, 2023 at 8:20 pm

    For voltage surge protection MOV may be better if provided after fuse or fusible resistance. All LED driver have MOV connected across line before bridge rectifier. I have repaired few LED drivers by just replacing fusible resistance and MOV, which got damaged by surge and they saved the rest of the circuit coponents.MOV used - 07D511k.

    • Parasuraman S

      July 16, 2023 at 10:37 am

      Good suggestion! Shall try it next time! Many thanks for your comments and suggestions!

  4. Henrique J. G. Ulbrich

    July 17, 2023 at 12:41 am

    Interesting report, Parasuraman. Indeed, adding these USB and radio modules helps to save and renew older devices. Thanks for sharing.

    • Parasuraman S

      July 17, 2023 at 9:09 am

      Many thanks for your comments and support!

  5. Waleed Rishmawi

    July 17, 2023 at 3:11 pm

    the right man for the job. I loved the modification job shared. I am sure you were disappointed that there were no capacitor to replace. LOL. have a blessed day

    • Parasuraman S

      July 17, 2023 at 11:12 pm

      Ha! Ha! Many thanks for your comments and encouragement, dear friend!


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