Can you use some help understanding

Discussion in 'Marantz Audio' started by disisme, Mar 18, 2017.

  1. disisme

    disisme AK Subscriber Subscriber

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    Hi
    Was hoping I might be so bold to ask for a bit of a tutorial on how a for instance marantz 2345 works , or at least for troubleshooting purposes a kind of Flow Chart ie if the unit is getting static on one channel or the other . If I'm going to learn this stuff for doing my own receivers as well as learn enough to gain experience and help others when and or if they have problems. I've learned quite a bit thus far and will be doing a recap on my unit but I'd like to learn more of if an amp is doing or not doing something well where does the preamp come into play , kind of a what is suppose to happen once you power on the receiver. If this is too much to ask I do understand.
    Thanks
    Lynn
     
  2. blhagstrom

    blhagstrom Mad Scientist, fixer. Subscriber

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    It is a long answer.
     
  3. disisme

    disisme AK Subscriber Subscriber

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    Yes I kinda figured it would be , sure would appreciate anything. I've been sitting back following what you's guys give for advice and guidance and would just like to understand a bit better without hijacking someone's thread.
    Thanks
     
  4. mbz

    mbz Active Member

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    346
    Location:
    Melbourne, Victoria
    I'm sure there are plenty of books and online tuts' that would
    do a decent job of explaining it. Below is a 5 minute effort.

    Basically, the amp, amplifies a signal, that signal coming from
    a source like a Tuner, phono or CD.

    The Phono is a special case. The Phono stage provides a "pre-amplifier"
    for turntables that don't have their own phono amp, ie, a dumb TT.
    After the phono stage the signal handling is the same as other
    inputs (Tape, AUX,,,).

    The signal then passes through a preamp stage (volume, tone controls,,,)
    and then onto the power amp and then onto the speakers/headphones.

    The signal handling (phono stage, preamp and power amp) is divided
    into left and right paths/channels. Sitting beneath the amp stages
    is the power supply which, yep you guessed provides power to
    the amp stages.

    OK, fault scenario, you have no sound or you have noise on one
    channel.

    Question, does it happen on all inputs/sources?
    If only phono input, then investigate the phono stage for the problematic
    channel.

    Conversely if it happens for phono/tuner/AUX... then don't waste your
    time looking at the phono stage. The next step would be to work out if
    the cause is the preamp or power amp stage. Some amps have PRE-OUT/MAIN-IN
    jacks at the back. This allows isolation/separation of the PRE and POWER
    amps, it also helps troubleshooting.

    Back to the fault scenarion, if you used the PRE-OUT of the faulty amp
    and connected it to the MAIN-IN of another known working amp and everything
    was OK/sounded teriffic then the conclusion would be that the fault is
    in your power amp stage, since when you replace it, all is OK (OK, it's
    a bit hard to follow but also difficult to concisely explain).

    The power supply is normally investigated for problems affecting both channels.
    More likely to be one central fault than a fault in each channel.

    Service manuals are available online, eg, hifiengine.
    They schematics look daunting but are just a logical connection
    diagram, signal flow is normally left to right, often with
    the left channel on top and the right channel below. The SM
    also contains the physical board layout and other things like bias
    procedure.

    Try down loading the Luxman SQ-505X service manual and take a look at
    the schematic, page 13? Don't go into detail, just get an overall view.
    Top half is the left channel. Bottom half with the empty boxes (duplicates
    of above) are the right channel. The middle layer contains the power supply.
    Also identify the phono stage (top left) and the PRE-OUT/MAIN IN jacks.
    Preamp to the left, power amp to the right of the jacks.

    I'm a newb trying to help out, hopefully some of the more learned AK
    members will chime in. Any errors/over simplification in the above...
    I'm a newb...
     
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  5. mbz

    mbz Active Member

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    prefer my fireblade...
     
  6. disisme

    disisme AK Subscriber Subscriber

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    Thanks mbz your 5 min explanation gives a lot of food for thought and much of it makes more scence compared to issues I've been following in other threads.
    Umm what's a fire blade?
     
  7. mbz

    mbz Active Member

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    346
    Location:
    Melbourne, Victoria
  8. Dearslayer

    Dearslayer AK Subscriber Subscriber

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    Ontario Canada
    Thanks MBZ for the explanation. As a newb myself I can appreciate all the short easy explanations that I can get. I wish there were a specific area here on AK that had maybe short videos on some of the the more common issues explained by the experts in laymans terms. Sometimes I'm guarded in the questions I ask because I know that the answers are gonna be intimidating to me, and I won't understand what some consider pretty straight forward but if I can take away even a small percentage of understanding each time a question is answered by the more experienced I consider it a huge leap toward eventually understanding the greater sum of it all. Onward through the fog.
     
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  9. disisme

    disisme AK Subscriber Subscriber

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  10. mbz

    mbz Active Member

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    Location:
    Melbourne, Victoria
    Yes, agree, there should be more knowledge sharing (Teach a man to fish...). There are many very knowledgeable AK members who spend considerable time helping
    others out. There are some good posts like how to test transistors, however this needs to be consolidated like you have suggested.

    I also feel intimidated, some of my posts/suggestions have been completely WRONG. Brush yourself off, get back on the bike, learn a little...
     

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