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5.1 Surround System fault

Discussion in 'Troubleshooting and Repair' started by Derek Payne, Apr 15, 2017.

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  1. Derek Payne

    Derek Payne

    6
    1
    Apr 15, 2017
    Hi

    I have a "One Concept" 5.1 dolby pro logik ssurround system which normally works very well. Its made by a company called Chal-tec gmbh, and thier website is www.elektronik-star.de.

    It is playing up, when you first turn it on it is fine you can change all the settings via remote control or on the front of the panel, but after about 5 minutes it becomes unresponsive to anything, although it is still working and the sound is fine, but you cannot turn it off or change volume or anything else. You have to turn it off on the mains and then wait for a while and turn it back on when it is fine for about another 5 minutes or so.

    Any guidance as to what the problem is would be greatly appreciated.
     
  2. davenn

    davenn Moderator

    13,672
    1,891
    Sep 5, 2009
    can you please be more specific .... I just saw a page of many devices and didn't see the one you were referring to

    sounds like a heat related problem
    there may be one part that is failing and overheating or it may be just poorly designed and a lack of heatsink on a specific part
     
  3. Derek Payne

    Derek Payne

    6
    1
    Apr 15, 2017
    Here is a picture of the cover of the manual, the system has been superceded, mine is about 8 years old.
     

    Attached Files:

  4. Derek Payne

    Derek Payne

    6
    1
    Apr 15, 2017
    I have had a look under the hood so to speak, and I think that the problem stems from the power supply as it is dual voltage supplying both 9v and 11.5v to separate parts of the board, and it is my theory that one is failing causing whatever part of the board it supplies to stop working. As it happens after it has been switched on for about 5 minutes it makes me feel that as the power supply is warming up it fails.
     

    Attached Files:

  5. davenn

    davenn Moderator

    13,672
    1,891
    Sep 5, 2009

    I did comment that it most likely a heating up fault ;)
    2 ways to find this out
    1) the finger tip test .... look for a hot component
    2) a can of freezer spray and gently spray individual components and see if the fault temporarily disappears
     
  6. Derek Payne

    Derek Payne

    6
    1
    Apr 15, 2017
    Hi

    I have followed your advice, I removed the board, turned the unit on and waited until it started with the fault, I checked all the components and come across one that was very hot to the tip of my finger, I blew on it to cool it down and the unit started working again, so I assume it is that component which is causing the problem. Although since blowing on it and getting it to work again, it hasnt developed the fault since and seems to be working, although the component I cooled down still feels too warm to my finger.

    The component has a triangle with a "T" inside it and the letters ABAH stamped on it with the numbers 7805A I have googled this number and there is a company based in the UK who have it listed on thier site as a "Semiconductor" here is thier link, if you could identify the exact one I would appreciate it, http://www.mouser.co.uk/Search/Refine.aspx?Keyword=7805A

    I have attached a picture of the component which I believe to be faulty ringed in red.

    Cheers
     

    Attached Files:

  7. duke37

    duke37

    5,364
    769
    Jan 9, 2011
    7805 seems like a 5V regulator. They normally have over temperature shut down so it is working correctly. The problem is likely to be in the circuit which the regulator supplies or poor thermal contact to the circuit board.
     
  8. Derek Payne

    Derek Payne

    6
    1
    Apr 15, 2017
    I tried soldering the joints, just to make sure none had gone dry, and now the unit is is permanent fault mode, so it is definately the component which is at fault, i probably got it too hot resoldering it.
     
  9. davenn

    davenn Moderator

    13,672
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    Sep 5, 2009
    make sure you didn't leave a solder blob there shorting out component legs .... never leave the soldering iron tip on the component legs for any more than a few seconds


    OK, if not that, get a replacement 7805 and whilst you are at it get a small heatsink ( that's if there is room between the top of the chip and the case of the unit) ...
    that is room to fit it ... there are low profile heatsinks available that glue onto the component they are cooling

    Will try and find an example
     
  10. davenn

    davenn Moderator

    13,672
    1,891
    Sep 5, 2009
  11. Derek Payne

    Derek Payne

    6
    1
    Apr 15, 2017
    I left it a bit longer to cool and it is working again now, will check again in about 30 minutes to see if it is going into fault mode if so will get another 7805 and heatsink as there is loads of room to fit it.

    Cheers
     
    davenn likes this.
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