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Hotpoint Subwoofer No Power Problem Repaired

By on July 5, 2014
subwoofer repair

 

 

 

 

 

 

 

My friend gave this subwoofer saying there is no any indication of life when he connects it to the power source. The problem started when the power resumed after a power failure. He said he did not switch it off during the power failure.

subwoofer repairsubwoofer repair1

When I opened I found only two printed circuit boards (PCB): Power board and the amplifier circuit board as shown below,

subwoofer repairssubwoofer repairing

I measured the continuity of the power cable. It was very okay. Then I shifted my concentration towards the power circuit board because the symptom was no power. There was no any visible symptom of component failure. My aim was to see the fuse if it was intact. I could not see the ordinary fuse on the Power board.

Using my Digital Multimeter I started diagnosing the components on the power board. The inductors, the bridge rectifier (all the four diodes) and the Metal Oxide Varistors (MOV) tested well. There was one resistor I expected to have a low ohmic value which gave me infinity on my meter. See the image below.

subwoofer repairings

The colour coding was orange, orange, silver and gold. I expected it to be 0.33 Ohms 5% resistor.

 

To my surprise it gave me infinity. Surely it was open. That’s when I realized that this Switch Mode Power Supply used a low Ohm resistor as a fuse (Fusible Resistor).

subwooferrepair

When I de – soldered it out I saw a marking on the circuit board showing a symbol of a fuse. Before I replaced it I connected a series 100 Watts bulb where the fusible resistor was. 

series light bulb trick

I powered the power supply and the bulb did not glow. Good sign!

series light bulb tricks

 Once i soldered a new 0.33 Ohm 5% resistor the radio got back to life. Glory to God!

luciano

Luciano Francisco Thomas Khware (Malawian) studied Electrical and Electronics at Comboni Technical College and at Polytechnic (University of Malawi). Currently, he is a student at Tangaza University in Nairobi Kenya.

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.

By the way you can check out his previous article below:

https://www.jestineyong.com/power-inverter-repair/

 

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44 Comments

  1. Yogesh Panchal

    July 5, 2014 at 3:20 pm

    Good repair thanks for sharing keep it up.

    Likes(2)Dislikes(0)
    • Luciano

      July 6, 2014 at 4:49 am

      Yogesh
      You are most welcome!

      Likes(0)Dislikes(1)
  2. Waleed Rishmawi

    July 5, 2014 at 3:31 pm

    very informative article thanks for sharing. I like the part when you said Glory to God, that is amazing to see and read that. amen to that brother.

    Likes(5)Dislikes(0)
    • Luciano

      July 6, 2014 at 4:51 am

      Hi Mr. Waleed,
      Yeah thanks!!, for me every success is God's Grace so i give Him Glory!

      Likes(1)Dislikes(0)
  3. Vishesh jain

    July 5, 2014 at 3:58 pm

    Dear Thomas,
    you have substituted a fusable resistor with a regular resistor.
    fusable resistors are special type of resistors which are designed to fuse (open) when an excess current flows through it.
    It is a protective device.
    it is a combination of a fuse and a resistor.
    I would recomend you to replace it with a fusible resistor or else connect a fuse of definite rating and a resistor in series.
    with regards.
    Vishesh Jain

    Likes(5)Dislikes(0)
    • Luciano

      July 6, 2014 at 4:55 am

      Vishesh Jain,
      I replaced with a 0.33 Ohm 5% fusible resistor not ordinary one.
      Thanks for your comment!

      Likes(3)Dislikes(0)
  4. wael fathe

    July 5, 2014 at 8:02 pm

    i think any resistor once its watt rating exceeded will be opened but the quickness of the process and whether it will be done fast enough before further damage to other components like bridge diode is some thing beyond my knowledge

    Likes(0)Dislikes(0)
    • Luciano

      July 6, 2014 at 6:00 am

      Thanks for your comment Wael

      Likes(0)Dislikes(0)
  5. Robert

    July 5, 2014 at 10:00 pm

    Good job Luciano. I hope the replacement was a fusible-resistor and not a regular resistor.

    Likes(1)Dislikes(0)
    • Luciano

      July 6, 2014 at 5:00 am

      Robert,
      Surely i replaced it with a similar value fusible resistor (check my last statement in the article). They are readily found so I accessed easily.
      Thanks for your comment!

      Likes(1)Dislikes(0)
      • Robert

        July 8, 2014 at 7:03 am

        I figured that you did, but the last statement just says resistor.

        Likes(0)Dislikes(1)
  6. HumbleStudent

    July 5, 2014 at 10:05 pm

    Thanks...I did learn from this.

    I thought the 100W bulb *should* glow...if there were current there at all. Replace the fusible resistor, and there'd still be no current through the component...
    Why is the absence of glow a good sign?

    Likes(1)Dislikes(0)
    • Momchil

      July 6, 2014 at 3:21 am

      The bulb has a higher resistance of like 2200 ohms I guess (I=U/R so 0.1 amps = 220/2200). If it get lit it means that there is power but there is something wrong with the rest of the board or other board is faulty/i.e. device needing more diagnostic/repair. The other devices like speaker have way lower resistance and so they should make a path for the current drawn and not the bulb.

      I think there is additional reason for it not being lit a good sign but I can't think of it now.

      Likes(1)Dislikes(0)
    • Luciano

      July 6, 2014 at 5:07 am

      Humblestudent,
      If the bulb glows there is a short in the circuit and if it doesn't that's a good sign. in my case the bulb did not give out light and there was DC voltage on the output stage supplying the amplifier and the display panel. If i had connected them during this test the radio could show the sign of life. i preferred testing it with a series bulb on no load!

      Likes(0)Dislikes(0)
  7. Abdul Haleem

    July 5, 2014 at 10:06 pm

    yes, you r right Vishesh Jain. It's difficult to find FUSIBLE resistors at normal electronic parts stores. It's an innovative and safe idea to use a fuse in series with a normal high wattage resistor. Thanks for your idea.

    Likes(1)Dislikes(0)
    • Luciano

      July 6, 2014 at 5:10 am

      Abdul
      Yeah thanks, my gratitude to Jain as well
      Thanks for the idea. I have learnt something valuable!

      Likes(0)Dislikes(0)
  8. Anwar Shiekh

    July 5, 2014 at 10:29 pm

    I agree it is crazy to replace a fuse with a resistor; however the original stripes (orange, orange, blue) seems to suggest the original was 33 Mohms, which might explain the open reading.

    Likes(0)Dislikes(0)
    • Luciano

      July 6, 2014 at 5:23 am

      Anwar
      Thanks for the comment. however I advise you to read my article patiently you will see where i wrote the actual colour coding of this fusible resistor: orange, orange, silver and gold which is 0.33 ohm 5 %!
      then down the lines i said i replaced it with a new fusible resistor of the same value.
      Thanks!

      Likes(0)Dislikes(0)
  9. as

    July 5, 2014 at 11:04 pm

    nice work show some tv work

    Likes(0)Dislikes(0)
    • Luciano

      July 6, 2014 at 5:59 am

      As,
      thanks so much,i will share once i get one repair!

      Likes(0)Dislikes(0)
  10. Merlin Marquardt

    July 5, 2014 at 11:28 pm

    Very good diagnosis and repair of a somewhat subtle problem. Do not understand the series bulb trick. Thank you.

    Likes(0)Dislikes(0)
  11. Luciano

    July 6, 2014 at 6:02 am

    Merlin,

    If the bulb glows there is a short in the circuit and if it doesn't that's a good sign. in my case the bulb did not give out light and there was DC voltage on the output stage supplying the amplifier and the display panel. If i had connected them during this test the radio could show the sign of life. i preferred testing it with a series bulb on no load!

    Likes(1)Dislikes(0)
  12. anwar Shiekh

    July 6, 2014 at 8:05 am

    http://www.token.com.tw/resistor/resistor-color-code.htm

    "If an additional fifth band is white, the resistor is fusible resistor"

    are you sure this is a fusible resistor?

    Likes(1)Dislikes(0)
    • Luciano

      July 7, 2014 at 7:58 pm

      Hi Anwar,
      Thanks so much for the link...in my case i believe the resistor acted as a fuse by cutting off and i believe in normal working condition it worked as a resistor, thus i named it fusible resistor!

      "Fusible Resistors contain both functions, as being resistor in normal condition and changed into fuse while abnormal current comes in to protect machine and equipment".
      i agree with you about the fifth colour band according to Tokenchina if its white then its fusible resistor.

      Likes(0)Dislikes(0)
  13. nanonet2011

    July 6, 2014 at 8:17 am

    very good advice friend, many times we "go crazy" and is looking for the damage that we do not give importance to the low resistance homiaje and it is a fuse. thanks for sharing it greetings from Colombia

    Likes(0)Dislikes(0)
    • Luciano

      July 7, 2014 at 7:57 pm

      Hi nanonet2011,

      Greetings from Kenya!

      You are welcome friend

      Likes(0)Dislikes(0)
  14. Joshua oloo

    July 6, 2014 at 2:04 pm

    Hi Mr.Luciano,Thanks for sharing the article with us.Its informative and to the point.keep it up and God bless the work of your hand.

    Likes(0)Dislikes(0)
    • Luciano

      July 7, 2014 at 8:01 pm

      Mr. Joshua,
      You are most welcome.
      where are you based in Kenya?

      Likes(0)Dislikes(0)
      • Joshua oloo

        July 8, 2014 at 1:44 pm

        Mr.Luciano,Am in Nairobi and suggest we can chat and know one another via facebook because am sure i can benefit alot from you on matters repair.God bless.

        Likes(1)Dislikes(0)
  15. peter

    July 7, 2014 at 12:07 am

    great job bro,thanks for sharing this wonderful article

    Likes(0)Dislikes(0)
    • Luciano

      July 7, 2014 at 8:02 pm

      Peter,
      you are most welcome bro!

      Likes(0)Dislikes(0)
  16. Imraz

    July 7, 2014 at 5:00 am

    Good Article with good diagnosis Mr. Luciano, I would like to suggest one thing, Please use a bulb holder instead of soldering wires direct to the tester bulb as in electronics we deal with dangerous voltages and safety should be paramount. Thanks for the article and keep it coming.

    Likes(1)Dislikes(0)
    • Luciano

      July 7, 2014 at 8:05 pm

      Imraz,
      Wow! you are hundred percent right! Your advice taken and consider it done.
      thanks a lot once again!

      Likes(0)Dislikes(0)
  17. Humberto

    July 7, 2014 at 6:52 pm

    Hi Luciano, good article and repair. almost all the times simple things are more difficult than nothing.

    Likes(1)Dislikes(0)
    • Luciano

      July 7, 2014 at 8:06 pm

      Humberto,
      You are right i give you very many thanks for the comment!

      Likes(0)Dislikes(0)
  18. Leburu

    July 7, 2014 at 7:59 pm

    I have been trying to learn about the light bulb trick on previous articles but I couldn't get it clearly but this article has nailed it and made it simple to an electronic enthusiastic like me.Thanks to everyone who has commented on it because I have managed to understand it through your discussions.

    Likes(1)Dislikes(0)
  19. Luciano

    July 7, 2014 at 8:16 pm

    Leburu,
    Thats the power of knowledge sharing. My heartfelt gratitude to Mr. Jestine for this informative Blog.
    Lets keep sharing!

    Likes(1)Dislikes(0)
  20. Andre Gopee

    July 7, 2014 at 10:52 pm

    Good Work Luciano. I repaired a Cheap power supply that had the same fusible resistor that had open circuit.

    Likes(1)Dislikes(0)
  21. Luciano

    July 9, 2014 at 4:54 am

    Andre,
    Thanks so much! I like your experience too

    Likes(0)Dislikes(0)
  22. Taring K Arioka

    July 21, 2014 at 7:36 am

    Thank you for your good work

    Likes(0)Dislikes(0)
  23. Raymundo Saura

    August 27, 2014 at 3:24 pm

    thanks for sharing sir nice article a good one for me a new in this world of electronic thanks again sir

    Likes(0)Dislikes(0)
  24. Dennis

    December 28, 2017 at 6:01 pm

    my subwoover is not desplaying the led and screen lights when i sewtches it on and can not be operated.what might be the problem friends?

    Likes(0)Dislikes(0)
  25. Pats

    March 25, 2020 at 5:52 pm

    Can someone assist me with HA1620s schematic diagram

    Likes(0)Dislikes(0)
  26. Ivan

    June 3, 2020 at 2:26 am

    thanks for the lecture

    Likes(0)Dislikes(0)

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