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Service Manual needed for Sony STR-DB930

Discussion in 'Datasheets, Manuals and Component Identification' started by Ton1, Jul 11, 2020.

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  1. Ton1

    Ton1

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    Jul 11, 2020
    Hello,
    Can anyone advise on how/where to obtain a service manual for the above receiver?
    Any information would be much appreciated.
    Thanks
    Ton
     
  2. Martaine2005

    Martaine2005

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    May 12, 2015
    Ton1 likes this.
  3. Ton1

    Ton1

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    Jul 11, 2020
    Brilliant, thank you so much Sir for such a quick positive reply.
    My receiver is over 25 years old and has never had any issues until this week when a few minutes after switch-on, a loud bang is heard from the front speakers and the display shows the activated "Protector" and I am assuming there is a short circuit somewhere.
    Although nothing has been touched/replaced, I have checked all the speakers wiring and connections and they seem to be in perfect order and switching back on after a few minutes the full operation is restored and nothing happens for a few hours or at all, but the following day, back on from cold, the Protector is triggered again.
    I have read some of the articles here regarding dry joints, overheating or dud output transistors and I will have to check all of that but in my experience repairing transceivers (amateur and cb alike) a faulty output transistor does not work intermittently, it is full-on or not at all, but then again, everything is possible in electronics.
    Would you have any ideas, hints up to the likelihood of this problem? I am almost convinced that it is down to a short somewhere and I am sure I will be able to find it now that I have the complete circuit diagram.
    I am very grateful for the info.
    Tony
     
  4. Martaine2005

    Martaine2005

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    May 12, 2015
    If it works sometimes and is 25 years old, it isn’t a short.

    Try replacing the electrlytic capacitoors. They dry out over time and will exhibit this behaviuor.

    Martin
     
  5. Ton1

    Ton1

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    Jul 11, 2020
    Thanks Martin. I will check that out and will let you know in due course.
     
  6. Ton1

    Ton1

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    Jul 11, 2020
    Hi Martin,
    Took the cover off and lifted the DC Board, checked out the two massive 15000uf - 71v electrolytic capacitors and found them to be charging and discharging normally and I cannot see any burn marks or discolouring signs on any of the components on this board. On my workbench, after replacing the board and switch-on, the voltage across the two caps (measured at the four cable terminal running out of it) is 61.8v and with all the speakers removed and just using a set of stereo headphones, the audio is nice and clear and there hasn't been any cut-off/protector display after more than three hours and everything inside the cabinet is running nice and lukewarm.
    I did a search for these caps and could not find any supplier offering a 71v version. They have either 63v or 100v that are quite pricey.
    I am going to reconnect all the speaker set up later on and see what happens but I am 100% sure they are all in perfect working order.
    Have you any suggestions?
    Tony
     
  7. bertus

    bertus Moderator

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    Nov 8, 2019
  8. Martaine2005

    Martaine2005

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    May 12, 2015
    Other than dry joints as you said earlier and thermal issues, nothing else comes to mind yet.
    Have a real close look for dry joints, use a magnifier.
    Sometimes wiggling components while using the magnifier shows what you wouldn’t normally see.
    For thermal issues, you can try spraying freezer spray on components like transistors and ICs.

    The bang through the speakers is probably the relays turning off.
    Have a real close look.

    Martin
     
  9. Martaine2005

    Martaine2005

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    May 12, 2015
    Not always @bertus . ESR is better than visual. But visually deformed capacitors are obvious.

    Martin
     
    bertus likes this.
  10. Ton1

    Ton1

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    Jul 11, 2020
    Hi,
    A visual inspection of capacitors or any electronic components for that matter is normally the first task any competent faultfinder would carry out. Bulging, leaking or discoloured capacitors and burnt-out resistors are easy to spot but when all the components, like in my case here, look more or less like when they were first installed, then the only way to find the problem is to test each one individually in or out of circuit for their relevant parameters. I wish it could be that easy on this piece of equipment but thanks for the link anyway.
     
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