Sony Power Supply Problem

Discussion in 'General Electronics Chat' started by ortiko, Nov 5, 2014.

  1. ortiko

    Thread Starter Member

    Oct 21, 2014
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    I have this sony receiver and it doesn't power on at all...

    Power Supply model: 09DAV-POWER-MR-MP-13
    I started looking the power supply and fuse on it are ok.
    At rectifier output i measure 32V dc

    The red circle the output is 8V and on pcb it reads 32-0 32-0
    So i suppose this is the problem but don't know how to find the defective part
    Every part on pcb looks ok...

    Any suggestions will be appreciated

    pssony.jpg
    pssony2.jpg
     
  2. Jony130

    AAC Fanatic!

    Feb 17, 2009
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  3. ortiko

    Thread Starter Member

    Oct 21, 2014
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    Thanks alot Jony130. That was a big help!
    I will replace the caps and see the voltage on Q901 and come back later.
     
  4. ortiko

    Thread Starter Member

    Oct 21, 2014
    64
    1

    without replacing the capacitors emitter of Q901 is 15,8 V
    Tommorow i will have C926; C912; C908 new and will replace them...
    I hope this will do the trick.

    with C908 on pcb i measured at below marks on picture:

    20141105_190436.jpg
     
  5. ortiko

    Thread Starter Member

    Oct 21, 2014
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    I have the PS circuit below.


    circuitpssony.JPG
     
  6. ortiko

    Thread Starter Member

    Oct 21, 2014
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    Have changed the capacitors with new ones and problem remains :(
    Strange thing is that volts at emitter of q901 is 1,6V
    Before i replace the caps it was 15,8 V

    Is the transistor defective? (Q901)
    Any idea what to check ?

    d901.jpg
     
    Last edited: Nov 6, 2014
  7. ortiko

    Thread Starter Member

    Oct 21, 2014
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    Can not find datasheet for the IC MR4020-7103 (IC921)
    Anybody know where to search ?
     
  8. Jony130

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  9. Alec_t

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    Sep 17, 2013
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    The schematic in post #6 shows both the base and emitter of Q901 strapped directly to Gnd. That can't be right?
     
  10. ortiko

    Thread Starter Member

    Oct 21, 2014
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    Well i am back with not so good news
    I powerd on the PS with 1,2 A fuse in place of FR929 and fuse blown and burned smell came from IC921 MR4020-7103 [​IMG]

    After that i replaced fuse (FR929) and without mains power connected i tested the resistance of IC921 and it is 28 ohms...

    So this IC is dead i suppose and hard to find for replacment ? [​IMG] [​IMG] [​IMG]

    In a store i looked i found only the one in first picture below(the burned out is second pic with long legs)

    Will this work for replacement if i use wires to connect all legs as the old one ?
    87513.jpg

    $(KGrHqJ,!pIFElNqME8qBR)LD9u8eg~~60_57.JPG
     
  11. ortiko

    Thread Starter Member

    Oct 21, 2014
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    Have MR4020 (pic 1 above) installed after long and hard soldering of the pins it is ok and think it is working fine but reciever dosen't power on again

    I need the datasheet of IC 901 STRF6138
    Could not find anything about it...
     
  12. Jony130

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    Feb 17, 2009
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    As for the fuse. Next time use a 75W or 100W instead of a fuse. If you still have a short the bulb will glow bright the whole time but after you get the short cleared the bulb should come on for a second or two then go out.
     
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