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2018-05-07

Onkyo A8470 - speaker relais not clicking - "servo operation" lamp not coming on - degraded glue on protection IC's pins

That was an interesting repair. A friend brought me his Onkyo amplifier. It did not switch the speaker relais on and the servo operation lamp did not come on. Both are controlled by the integrated protection chip Toshiba TA7317 and after some tests and measurements, it became pretty clear that the error had to be there. The amp produced a signal just up to the relais and there was no DC on the output, either.

I remembered a YouTube video where a guy said that in old devices a certain type of glue would degrade and become ever so slightly conductive. Just enough to cause sensitive circuits to malfunction. And what have we got here? A big splash of that brownish gunk right over the pins of the protection IC! They had glued the patch wire to the board with it and splashed glue all over the place.



I cleaned it with acetone and the amp came back to life. I resoldered everything just to be safe that it wasn't a dodgy solder joint.



As a precaution I also took care of the other glue spots:


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3 comments:

  1. Unknown5/18/2018 8:46 AM

    Great job! These faults also happen in the older lcd tv's. Good to see a new post , it's been a while!

    ReplyDelete
    Replies
    1. Alpengeist5/19/2018 6:54 PM

      It is actually not a new post. I tried to get rid of a spammer, who had chosen the first version of this post. Didn't help. He picked another one now. :-(( Well, the TV repair hobby has stagnated. Dead mainboards and broken screens are the normal case these days. It used to be more fun.

      Delete
  2. Anonymous6/17/2018 9:33 PM

    It still is fun to repair electronics with 5$ of spares and a collaborative brain !

    ReplyDelete

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