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How To Repair Avvox Mixer Amplifier With No Sound

By on July 15, 2016
mixer amplifier repair









mixer amplifier

The complaint of this Avvox Mixer Amplifier was no sound even when the Music and Mic volume control were set to almost half-see the photo below:

troubleshooting amplifier

The first thing I did was to remove the cover and power up the set and check on the Dc supply voltage. There was a 3 pins connector.

First pin is the cold ground, center pin is -12 volt and 3rd pin is + 12 volt. Checking on the +12 volt pin it showed 12.3 volt which mean it was good and within specification.

how to repair mixer amplifier

When I checked on the -12 volt pin, the meter showed only 0.16 volt. This in fact was a good sign because I can start to trace from this pin. It can be circuit track broken, bad component or even shorted component between the -12 volt line to cold ground.

fixing mixer amp

By tracing the -12 volt line, I actually found a 12 volt zener diode that was shorted. This is the reason why I did not get the -12 volt. Further checking on surrounding/corresponding components did not show any other bad components thus I concluded that only the zener diode itself shorted.

repairing amp

Spare parts for zener diode is very easy to get from any electronics shop. The 12 volt zener diode part number is 1N4742- 1 watt

how to fix a mixer amp

After fixing in the new zener diode the sound came back. Sadly I can’t proof to you that the mixer amplifier already working but I hope  you will understand that this is an article and not a video.

mixer amp repairs

All the best!


This article was prepared for you by Suranga Bandara who owns an Electronics repair shop in Anuradapura, Sri Lanka.

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Note: You may check out his previous repair article in the below link:

and related article by Parasuraman:





  1. Parasuraman S

    July 15, 2016 at 12:41 pm

    Good job! Thanks for sharing!

  2. Yogesh Panchal

    July 15, 2016 at 2:27 pm

    Good job! Suranga.

  3. S Ramachandran

    July 15, 2016 at 4:24 pm

    Very good job done and appreciate your technical skills.

  4. Anthony

    July 15, 2016 at 5:22 pm

    Terrific thorough repair Suranga ! Thanks for sharing here with us,

  5. Albert van Bemmelen

    July 15, 2016 at 9:38 pm

    Quite an impressive Mixer with those nice Led Lights this repair! Thanks for sharing.

  6. Humberto

    July 15, 2016 at 10:29 pm

    Hi Suranga, good repair. I'm repairing a PC SMPS and it shows between +7v and +8v in the Stand By-out and the real voltage must be +5v. And know what? I've drawn the circuit doing the Reverse Tech and have found the Zener Diode of this stage broken in two pieces. I haven't finished this mend yet. But it's a similar case. Congratulations and keep up sharing your experiences.

  7. biruk aweke

    July 16, 2016 at 12:55 pm

    Congrat. great man.

  8. Hicham

    July 16, 2016 at 10:51 pm

    Well done, Thanks for sharing friend.

  9. Mark

    July 17, 2016 at 6:10 pm

    Hey Suranga,
    Thanks for another great repair. Good to see it was a simple one this time!

  10. Mark Tembo

    August 16, 2016 at 9:52 pm

    Excellent article!

  11. anil s suryawanshi

    September 5, 2016 at 1:05 pm

    sir iwant name for advance new laptop repaire books with chip level repairing and my second my laptop noising and laptop doesnot work how hardisk repair


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