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Power supplies not working on Sony ICF-SW7600G

Discussion in 'Troubleshooting and Repair' started by amouse76, Jan 4, 2021.

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  1. amouse76

    amouse76

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    Jan 4, 2021
    I just pulled out my old Sony ICF-SW7600G (purchased in 1994, IIRC). Now, whether using fresh AA batteries or an external 6V DC power supply, I just get a flashing "0:00" and the "Battery empty" indicator is on. If I disconnect power and remove the batteries, the flashing "0:00" continues, as does the battery empty indicator, no matter whether the power switch in is the on or off position, and this continues for some time, presumably until some internal capacitor is discharged.

    The last time I used this some years ago, the DC input was a bit touchy, requiring the power jack to be pressed a bit to make good contacts. Not sure if this is an issues with those contacts, though, since battery operation is also failing.

    Any suggestions for troubleshooting this, and identifying the fault?

    Thanks -
     
  2. Martaine2005

    Martaine2005

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    May 12, 2015
    Hi, there would be the usual suspicion of electrolytic capacitors. This Youtube video may confirm this.


    Martin
     
  3. amouse76

    amouse76

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    Jan 4, 2021
    Hi Martin - Thanks. The difference I see is that, unlike in the video, the radio doesn't even power on normally. FWIW, the light doesn't even turn on when I press the light button on top (with fresh batteries). I've seen references to failed capacitors causing tuning problems/failures for these radios, but nothing for apparent power supply failure.

    I have tried pressing the reset button inside the battery case.
     
  4. Harald Kapp

    Harald Kapp Moderator Moderator

    11,522
    2,654
    Nov 17, 2011
    The DC input jack has a built-in switch that disconnects the battery from the power supply when a plug is inserted. See service manual :
    upload_2021-1-5_11-9-33.png
    If that jack is defect or has bad solder joints (as indicated by it being "a bit touchy") it may disconnect the battery while not making good contact for the external power supply. I only wonder why the LCD would operate to indicate a low bat, but who knows.
    Start by re-soldering all the pins of the DC jack. That may alleviate the issue.
     

    Attached Files:

    Martaine2005 likes this.
  5. PETERDECO

    PETERDECO

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    Dec 19, 2019
    If resoldering doesn't work, spray the jack with contact cleaner or WD-40. The contacts may be dirty.
     
  6. amouse76

    amouse76

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    Jan 4, 2021
    Thanks - will try those suggestions and report back.
     
  7. amouse76

    amouse76

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    Jan 4, 2021
    Finally got some good magnification and had time today to dig into to. It turns out some solder connections had cracked at the DC - input jack. SImply re-soldering these restored the radio to working condition - the tuning is solid so the caps seem good. Thanks Harald!

    Strangely, battery operation doesn't work. Will have to poke around a bit more, but appreciate the help so far.
     
  8. bertus

    bertus Moderator

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    711
    Nov 8, 2019
    Hello,

    When the radio does not work on the battery, the battery holder or the switch in the DC connector can be a problem.
    The switch can be checked when no battery is in the radio and measure the contacts with an ohm meter.
    When there is no plug in the connector, the switch should be closed.

    Bertus
     
    Martaine2005 likes this.
  9. Vempatib

    Vempatib

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    May 26, 2021
    Amouse76 I’m having the exact same problem with my old ICF 7600G. Can you help me walk thru the fix ? I’m not a hands on engineer
     
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