Question about Audio & Video Receivers

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I have a marantz sr-18U that came with a bad center channel. I took the amp board with a good center channel out of another sr-18U and put it in. It burned up the good center channel on this board too. I thought the problem was in the board, but it must be something else since it burned up the good one too. I have enough parts between the two of them to rebuild the center channel but I think it is just going to keep burning up the center channel. Any idea what the problem could be?

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  • 4 more comments 
  • ssryan2 Feb 12, 2009

    How would you fix an over voltage supply to the center channel. I haven't checked it yet but just wondering what the cause would be.

  • ssryan2 Feb 12, 2009

    what would cause the center board to receive too much power?

  • ssryan2 Feb 12, 2009

    I want to know how to FIX it. If that turns out to be the problem. I'm not home right now so I can't test it.

  • ssryan2 Feb 14, 2009

    Can anybody tell me if the sr-18a and sr-18u are the same thing? I'm trying to find a service manual, but can only find sr-18ex or sr-18a.

  • ssryan2 Feb 17, 2009

    OK, I have rebuilt practically the entire board 4 times and it keeps burning up the same components. Can anybody tell me what might be causing the over voltage supply to the center channel?

  • ssryan2 Feb 17, 2009

    anybody?

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8 Answers

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  • Master
  • 4,234 Answers

I don't have service info on this so we'll need to rely on experience with audio. What parts are burning up? I'll try to walk you down the diagnosis path. This may take a few iterations, but we should be able to resolve this. If the amp section for the center speaker uses discrete transistors, remove the output transistors completely and fire up the receiver (not literally of course...) and measure the voltages on each of the three pads and post them here.

I'll post the next steps based upon the voltage readings.'

Dan

Posted on Feb 17, 2009

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  • Master
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Check all the capacitors in the power supply section (well all the boards)... if any feel swelled up on the tops or appear to be leaking.... they have failed and need to be replaced.

Posted on Feb 17, 2009

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  • Master
  • 6,966 Answers

Hi and welcome to FixYa,

May I offer an alternative view? Almost always, the +/- power supply of the center amp would be common to all the other amps. Additionally, it would be very rare if regulators are utilized in the finals/outputs and therefore would be unlikely for the +/- supplies to go high. Alternative possibilities are:

  • shorted center speaker/speaker wires;
  • faulty pre-amp section;
  • faulty sound processing board;
  • shorted/leaky decoupling capacitors (1 ~ 2.2 uF).
A possible test is to check for the absence/presence of DC voltage at the input wire of the center amp. With the unit selected to any unused Audio/Line INPUT, the input wire going to the center amp should read 0 DCV.

Additionally, the difference in the last 2 characters often indicate regional versions. Regional differences include AC power in (120, 220, 240 & 50 or 60 Hz) and tuner/frequency stepping/separation.

Good luck and thank you for using FixYa

Posted on Feb 14, 2009

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  • 326 Answers

Its not exactly the same but the system and settings are near to same so you can continue with that service manual.that will give you the fair idea of fixing.and also work for you.
thanks.
please do rate the solution.

Posted on Feb 14, 2009

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  • Master
  • 547 Answers

It could be you should contact

  • us.marantz.com/Products/296.asp if it's not that old thay do have warenty
  • Marantz America, Inc.
    100 Corporate Drive
    Mahwah, N.J. 07430-2041
    General Office hours:
    8:30 AM to 5:30 PM ET, M-F
    Tel. 201-762-6500
    Fax. 201-762-6670

    Parts Support hours:
    9:00 AM to 5:00 PM ET, M-F

    Tel: 201-762-6392

    Tech & Operational Support hours:
    9:00 AM to 5:00 PM ET, M-F

    Tel. 201-762-6666
    Fax. 201-762-6687 Parts
  • Posted on Feb 12, 2009

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    The centre board may be receiving too high voltage power supply .it can be due to the fluctuations that come in power supply at many a times.just check the board for the burnt out capacitors.test all the junctions with a volmeter and replace the burnt out or faulty parts.its a common problem and will get solved easily at a minor cost.nothing much to worry about.

    Posted on Feb 12, 2009

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    • Audio & Vide... Master
    • 4,806 Answers

    Hi there
    Have a look for any burned out capacitors or resistors as this sounds like its more to do with the center board receiving too much power.

    Good luck and thanks for using Fixya!!

    Posted on Feb 12, 2009

    • 1 more comment 
    • Lee Hodgson
      Lee Hodgson Feb 12, 2009

      like i said faulty capacitors, resistors bad circuitry and of course semiconductors and power controllers themselves, any one of these could be causing too much power or even feed back

    • Lee Hodgson
      Lee Hodgson Feb 12, 2009

      welcomejee is right, i suggest you get a volt meter and do some testing, check the continuity between points, ckeck the capacitors and resisters for the correct voltage, the capacitors will say the voltage on them so a good magnifying glass would be an advantage so can read the components

    • Lee Hodgson
      Lee Hodgson Feb 12, 2009

      leave this post open until you get home, then log back on here, we will be able to help you much further if you could work on it at the same time. What we need you to do is test the components.



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    Problem would be over voltage supply to center channel board. Please check supplied voltage to center channel board and that should be accurate as per written in manual / PCB connector.

    Posted on Feb 12, 2009

    • 1 more comment 
    • Shahid Electronics
      Shahid Electronics Feb 12, 2009

      I told you cause of problem. To check voltage you need Digital
      Volt Meter.

    • Shahid Electronics
      Shahid Electronics Feb 12, 2009

      if you want to do it yourself then have service manual of amp, soldering iron, volt meter etc.
      You should have experience of electronics repair and basic electronics knowledge.

    • Shahid Electronics
      Shahid Electronics Feb 17, 2009

      Do you have related schematics or service manual?
      If yes, please email me welcomejee@yahoo.com to help you as I don't have it.


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