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Denon AVR 1804 amp won't switch on

Discussion in 'Troubleshooting and Repair' started by bushtech, Oct 25, 2016.

  1. bushtech

    bushtech

    888
    139
    Sep 13, 2016
    Grabbed the remote yesterday to switch on the amp, pushed button and nothing happened:(. Checked remote working by shining it at my phone camera and pressed button = working. Opened unit, checked fuse = working.Checked power cable, 220VAC arriving on board and red pilot light lit up as usual.

    I wanted to insert a photo here but can't find the option so will try again in a second post.
     
  2. bushtech

    bushtech

    888
    139
    Sep 13, 2016
    AVR1804ps1.jpg
    Upload file not visible, probably my rubbish internet connection.
    Anyway, the plug at A supplies power to the transformer at B.With the unit on, if I pull the plug at A and probe the pins I get no voltage there. The plug at C supplies power to a small board at D, there is power there as pulling that plug kills the red pilot light.

    Can somebody suggest what I can check. There is no burnt smell, but I don't hear the relay which normally clicks when I switch on
     
  3. bushtech

    bushtech

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    139
    Sep 13, 2016
    One of the 2 big caps near A and C is slightly bulged on top. Do they come into play at switch on or only later when amp is being used?
     
  4. davenn

    davenn Moderator

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    Sep 5, 2009
    they will most likely be smoothing caps in the PSU section
    replace them both. If one is already bulging it is stuffed and the other one if probably not far from it
     
    bushtech likes this.
  5. bushtech

    bushtech

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    Sep 13, 2016
    Thanks davenn. Could they be the cause of the amp not switching on or do I need to keep digging? I see they are Samyoung DL (DL =audio) 63V 1200μf 85C caps. Quite big 31mm dia x 63mm. Going to be nearly impossible to find in South Africa. Have already checked RS here. What would be a decent replacement or should I try for Samyoung again?
     
  6. davenn

    davenn Moderator

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    I wouldn't worry too much about brand unless you can find online evidence that they are bad.
    Also if possible use 105 deg temp ones.

    get in there with a 1" paint brush and a vacuum cleaner and get rid of all the crap on the board, it's really yucky. It may help you find hidden faults.
    Suspect every electro cap that is in a position with respectable voltages across them or ones close to heatsinks << I can see a few
     
    bushtech likes this.
  7. bushtech

    bushtech

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    Sep 13, 2016
    Thanks again davenn. Will do on the cleaning. Most of the replacement caps that I have found so far with my sucky internet connection are much smaller. Can I go to 1500μf and stick 2 of them in parallel?
     
  8. bushtech

    bushtech

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    Sep 13, 2016
    It doesn't look as if Samyoung make this cap anymore. The closest one I can find is 3300uf here: https://www.samyoung.co.kr/download/large/DL.pdf

    So I will probably be looking for a cap from a different manufacturer. I will go for 105C as davenn suggested but how far can I venture from the original spec. Voltage and capacitance wise?
     
  9. davenn

    davenn Moderator

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    you can parallel 2 x 1500 to get 3000 if needed. are there some ~ 3000uF ones in there ?

    as long as the voltage is the same or higher, it wont be a problem .... and try and stay within ~ 10% of the value of the existing one
     
    bushtech likes this.
  10. bushtech

    bushtech

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    Sep 13, 2016
    Ooops, I obviously don't know what I'm talking about. I was concerned about the much larger size of the original 1200μf caps. I thought if I got 2 x 1200 and stuck them in parallel I could equate to the larger sized caps.

    When you say ~10% are you talking voltage or capacitance?
     
  11. bushtech

    bushtech

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    139
    Sep 13, 2016
    Stupid me :mad:
     
  12. davenn

    davenn Moderator

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    sorry, I see that was a little ambiguous


    for capacitance .... try and stay within ~ 10% of the value of the existing one
     
  13. bushtech

    bushtech

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    139
    Sep 13, 2016
    10% doesn't leave me much room = 1320μf. My big concern is the size difference. Orig caps 31 x 63mm. The ones I'm seeing are generally less than half the size
     
  14. eKretz

    eKretz

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    Apr 8, 2013
    Smaller won't hurt. Larger can be a problem if there is not enough space for them. Newer higher quality caps are usually a lot smaller than older ones.
     
  15. davenn

    davenn Moderator

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    A 1500 cap will be OK instead of a 1200uF

    a smaller value, as eKretz suggested, specially if significantly smaller value, will be a problem in PSU circuits where they are used for smoothing as
    they wont give the same filtering amount and it will lead to more ripple on the DC rail(s)


    Dave
     
  16. bushtech

    bushtech

    888
    139
    Sep 13, 2016
  17. bushtech

    bushtech

    888
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    Sep 13, 2016
    I could probably modify the snap in connectors to make it work
     
  18. bushtech

    bushtech

    888
    139
    Sep 13, 2016
    Scrap that. Min qty =800, Not in stock, lead time 11 weeks

    Back to the drawing board
     
  19. eKretz

    eKretz

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    Apr 8, 2013
    Yes, davenn misunderstood my comment, which was in regard to physical size (as bushtech mentioned as a concern in the post right before mine). Definitely do not go lower in capacitance when replacing caps. As Dave previously noted - slightly higher capacitance is okay, and higher voltage is okay.
     
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  20. eKretz

    eKretz

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    Apr 8, 2013
    bushtech likes this.
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