Quiet center channel on a Yamaha RX-Z1 a/v receiver

Discussion in 'The Projects Forum' started by mnguye23, Jan 31, 2014.

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  1. mnguye23

    Thread Starter New Member

    Jan 31, 2014
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    Hello all, first post here--which is kind of a shame since I frequented this forum quite often a couple years ago when I was getting my degree :D.

    I have a RX-Z1 receiver that has a very very quiet center channel. I can only barely hear any sound out of it at near reference levels. I've confirmed that all the other channels work, save for the rear-center channel. They appear to either be sharing a signal, or power. Based on the schematic I attached from the service manual, I tested the voltages at each transistor and found them to be okay.

    My question is, where do I go from here? I've seen other threads where people with similar problems are guided towards verifying proper supply voltage--but since I'm seeing 60VDC or -60VDC wherever I'm supposed to, wouldn't that indicate the supply voltage is fine? Should I try looking further upstream than what is dictated on that page of the schematic?

    Thanks very much in advance!
     
  2. bountyhunter

    Well-Known Member

    Sep 7, 2009
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    what is the music source? Most sources don't have five channel (with center). The TV source on mine puts out all five but most stereo sources don't.
     
  3. mnguye23

    Thread Starter New Member

    Jan 31, 2014
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    Well I have a computer playing out to the receiver via optical toslink. This configuration works on another Kenwood receiver I'm using in the interim. I did my original tests using the built in test tones however.
     
  4. GopherT

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    Nov 23, 2012
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    Go through the set up. You may need a tv connected to see the display. The setup tells the TV which speaker configuration you have. 2, 3, 4, 5 or more with/without sub.

    Sometimes the setup clears on power failure.

    As said above, center channel not used in most music. It will have the Dolby digital or DTs logo on the cd. If the music is from iTunes, very unlikely to have surround sound track as they want to make it as compact as possible for quick file transfer. Also, streaming like PANDORA is also simple stereo.

    Your receiver may have a virtual surround processing capability. All in the setup though.

    Good luck.
     
  5. mnguye23

    Thread Starter New Member

    Jan 31, 2014
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    I don't believe setup is the issue. I said before I used the built in pink noise test tones, which are part of a diagnostic menu on this receiver. Every channel including surrounds play at normal volume. Only the center and rear center require reference levels to hear the test tone, which is barely audible.
     
  6. GopherT

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    Nov 23, 2012
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    The built in test tones broadcast on all channels because it it checking if you really had a speaker attached or not. The noise is not really pink, it is a very fast frequency sweep to see how the receiver output is actually reproduced and received by the microphone.
     
  7. mnguye23

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    Jan 31, 2014
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    In any case, I've done more tests and have confirmed that the center channel does have a very quiet output while watching a movie in 5.1. What else can I check, hardwarewise? The schematics provide a signal path that I can check, though not all the test points are easily accessible to me without some major deconstruction. Is it possible for collector and base voltages on an output transistor to be okay according to a multimeter but for the transistor to be failed in circuit? Or maybe there's a cold solder joint somewhere? Where could I try looking?
     
  8. GopherT

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    Now check the attenuation settings in the setup. It controls how much surround effect (non-center channel) vs. dialog (center channel) you get. Settings are usually off, day, evening and midnight. You might want to start with off.
     
  9. mnguye23

    Thread Starter New Member

    Jan 31, 2014
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    There is no attenuation that has been set.
     
  10. wayneh

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    Sep 9, 2010
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    On my Yamaha, I can do a firmware update, or a reset. If you can, you might consider a reset to factory settings. Maybe it's become confused somehow. I'd also take a hard look at the speaker connections and wires. Sometimes the simple solutions are the hardest to find.
     
  11. bountyhunter

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    Sep 7, 2009
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    My receiver has separate volume level controls for every speaker set, it's possible to accidentally set the center channel too low or high. As somebody else mentioned, the CPU that runs everything may just have lost it's marbles and set it wrong.
     
  12. mnguye23

    Thread Starter New Member

    Jan 31, 2014
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    A factory reset did not solve the issue. It just strikes me as strange. If it were truly just a software problem, why does the rear center exhibit the same symptoms as the front center channel, when they are both individually tuned by the user? I'm beginning to wonder if the DSP itself or a part on the DSP board has failed.
     
  13. GopherT

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    That is kind of the failure mode, one or two channels at a time. If it is dsp-related, reconfigure the software for 4.1 output or buy a new one. In 4.1, the dialog is sent to the fron two channels.
     
  14. mnguye23

    Thread Starter New Member

    Jan 31, 2014
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    My impression is that since I can still hear faint dialogue/information coming out of the center channel with the unit turned all the way up, perhaps the DSP chip itself hasn't failed. I went through the schematic again to see whether or not the center channel and rear center channel are joined somewhere, and they are, at IC34. Reading the datasheet on this reveals a little bit of info...apparently there's a mute function on Pin 15. The trace leading to Pin 15 on the Center/RearCenter IC also leads to Pin 15 on the Left/Right IC, so I doubt that this is the issue, given the Right and Left channels work fine. But I think I may check out the other voltages here when I find the time, and start working downwards.
     
  15. gtro127

    New Member

    Jan 19, 2016
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    I had a RX-V1 which is very similar in design. It had same problem. The solution ended up being poor contacts on one of the multi in or out put connectors(sorry I can't remember which). The signal went through this path. I just took some electronic cleaner(de oxit will work fine) put on end of rca cable & go in and out about 30 times to clean contacts. Make sure its a loose fitting cable to do this cleaning. If you go in & out with something tight fitting such as monster cable or AR you may end up pulling out connector. Hope this helps
     
  16. wayneh

    Expert

    Sep 9, 2010
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    Two year old thread. The thread starter is likely long gone.
     
  17. gtro127

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    Jan 19, 2016
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    Probably so but maybe info will help someone.
     
  18. ScottWang

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    Aug 23, 2012
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    When you reply to an old thread, all the Participants will get a alert, but they may not want to receive.
    So, please don't reply to an old thread again.
     
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