Adjusting Offset/Bias and other basic? things on Cr 2040 (help?)

Discussion in 'Yamaha' started by 0r0b0r0s, Nov 14, 2017 at 8:22 AM.

  1. 0r0b0r0s

    0r0b0r0s New Member

    Messages:
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    Hi all,

    The good people in the general board suggested I open one up here, in the dedicated Yamaha forum. This was my initial post, suggesting I test the offset and how to do it:

    http://audiokarma.org/forums/index....estroy-a-yamaha-cr-2040.796319/#post-11023662

    I got 203MV and 107MV DC using his technique.

    I am a true amateur and basic multimeter use is about all I can do. I MIGHT be up for adjusting the offset/bias if you think it's a good idea, otherwise I just want to install new bulbs and not break anything.

    As I said in the main thread, I don't care about the FM tuner, I'm just using it as an amp for digital music coming off my computer - it will live under my desk, unseen but not unloved.

    Any hints? Suggestions?

    --Oroboros
     
  2. 0r0b0r0s

    0r0b0r0s New Member

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    Oh also a quick question: they suggested I use compressed air and blow out the crud inside; can I just use a vacuum with a soft attachment? As long as I don't whack anything too hard will this be OK?
     
  3. 0r0b0r0s

    0r0b0r0s New Member

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  4. macyjrm

    macyjrm AK Subscriber Subscriber

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    Disconnect speakers. Make sure you are measuring the same speaker outputs as you have selected on the front panel.
     
  5. clinic-audio

    clinic-audio all on YAMAHA untill 1990

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    Location:
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    Hello

    I got 203MV and 107MV DC using his technique

    where are you taking measurement ?? What voltmeter do you use ?
    203mV and 107mV is not possible if your relay is working after switch the power on .
    Bias and offset are measured without signal , level at zero and with load connected on A speaker (with speaker selector on A position) on CR2040
     
  6. 0r0b0r0s

    0r0b0r0s New Member

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    Oh, hmmm I had some cheap speakers hooked up to A, and I was told to check B after setting output to A+B. Is this incorrect; I should set the speaker output to A but check B (A has speakers wired in?)?
     
  7. mbz

    mbz AK Subscriber Subscriber

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    Location:
    Melbourne, Victoria
    First up, RELAX. If you've made a "mistake" in the past then so what.

    Download the service manual and follow the procedure for checking the dc offset.
    203mV is certainly too high but probably not high enough to trip protection so you can continue to measure at the speaker terminals.
     
  8. macyjrm

    macyjrm AK Subscriber Subscriber

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    Location:
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    Disconnect all speakers. Volume knob to zero. Select A speakers on front panel. Measure DCV at A speaker terminals on rear panel.
     
  9. avionic

    avionic " Black Knights " Subscriber

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    Fort Dodge, Iowa
    Or use the designated test points in the service manual.
     

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