BT2025 IC (TEA2025 IC) Shorted To Ground

By on September 22, 2018
made bridge rectifier

 

 

 

 

 

 

 

 

 

Fault Symptom: front panel power indicator light blinking & no sound output

Philips 2.1 speaker repair

This symptom simply indicates problem in Power Section hence I have opened the speaker from backside & pulled out the circuit for further troubleshooting.

how to repair speaker

Surprising! No transformer inside.




On visual inspection nothing found suspicious I turned back the PCB and found rectifier diode (look like someone have tried to repair the unit before)

how to fix speaker

I have started the fault finding and found all these diodes are shorted while tested with using multimeter on continuity mode.

I have checked surrounding components found ok but have in one doubt about this IC in power section near fuse because it gets very HOT.

yh-111 ic

I have googled but not found any data about this IC. So decide to take a chance to check the effect by replacing the diode. Hence I have replaced all the four diodes.

four diodes

After powering “ON” the unit I have seen the LED power Indicator Light is ON and it is not blinking. So I have connected the speakers to the mobile phone still there is no output. So my doubt about that IC again leads me to that section. I powered off the speakers and touched that IC still it is very hot to touch.

I am bit confused what to do Now because without that IC DATA it is difficult to find equivalent also.




So I have put the unit beside. After finishing another work in the morning I have again took this unit for repair in the evening with refreshed mind.

I have started tracing the circuit. On testing the power regulator IC voltage on pin no.1 I/P voltage showing .6V instead of 12V DC. (This regulator is supply 5V to audio amplifier on IC pin no. 16) so I powered OFF the unit and checked this IC with multimeter in continuity testing mode I found this regulator IC is short.

7805 ic

Further traced up to the audio amplifier IC and on testing continuity on the supply pin of audio amplifier IC it shows short with Ground so for confirmation I have removed the IC from the PCB and tested again. When removed the IC I found burnt mark on the PCB.

burnt mark under ic

tea 2025 ic datasheet

 

tea2025 ic bad

Replaced the IC and powered the speaker yes this is my final attempt and I did it.

philips speaker repair

I have now connected the speaker and now it is working. For full fill my curiosity about that 8 Pin IC Heating in power section. I have touched the IC & found it is Normal Now no heating.

This article was prepared for you by Yogesh Panchal who works as a Computer Hardware Engineer in Mumbai India.




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Note: You can check his previous repair articles in the link below:

http://www.electronicsrepairfaq.com/mobile-adapter-repairing

 

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7 Comments

  1. Parasuraman S

    September 22, 2018 at 7:22 am

    Excellent trouble shooting without leaving! That's what is required in Technicians! You are a marvel and would do anything to set right things!

    Likes(3)Dislikes(0)
    • Yogesh Panchal

      September 23, 2018 at 4:02 pm

      Thank you Sir,

      Likes(0)Dislikes(0)
  2. Albert van Bemmelen

    September 22, 2018 at 12:23 pm

    Good job Yogesh. You said "no transformer inside" but there was one safety smps transformer visible on the second photo? No transformer would have been dangerous when touching the audio wires.

    Likes(0)Dislikes(0)
    • Yogesh Panchal

      September 23, 2018 at 4:27 pm

      Albert,
      Generally in this type of speakers manufacturers are using external power adapter or a step down transformer inside the box.in this circuit this transformer is used for DC to DC converting because already i am getting 18v Dc on primary side capacitor and the same on secondary side capacitor. do you have any idea about that 8 pin IC marked with YH-111? because i have finished this job in hurry because customer need it very urgent.

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      • Albert van Bemmelen

        September 24, 2018 at 12:48 pm

        Understood Yogesh. The solderside of the board you showed had on the right a dangerous marking sign with this safety '!' marking in it and both sides of this board are distinctly separated from each other which is marked by the vertical white line in the right board middle like is the case in smps 110VAC/230VAC to DC supplies.
        I guess that if it is a YH-1117 which is a smd voltage regulator the following number gives you the voltages it puts out regulated. But if it is a standard LM111 it likely will be a voltage comparator?: http://www.ti.com/lit/ds/symlink/lm111-n.pdf
        To be sure of this you could test this IC in a tester/test circuit or replace the chip with a LM111?

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  3. R Murali

    September 24, 2018 at 12:11 am

    Great effort in finding the root cause . Thank you for sharing.

    Likes(0)Dislikes(0)
  4. Humberto

    September 26, 2018 at 12:18 am

    Hi Yogesh, you performed a professional troubleshooting.

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