Finding the bad guy in my reciever - Marantz PS\SR-4500

Discussion in 'The Projects Forum' started by Alon Perelmuter, Apr 23, 2016.

  1. Alon Perelmuter

    Thread Starter New Member

    Apr 23, 2016
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    Hello Friends,
    I would like to get advice, how can I find the problem in my Marantz.
    The problem is - Front-Channel not working good. There are only very low freq. to the right speaker. not mid or high. sometimes there are but really crunchy.
    I found the AMP circuit (bellow the file - page 14). I checked with my FLUK and found that both of the power transistors (the D2390 and the B1560) or acting good (voltage is ok). (BTW how is that I have 0.7 between Collector and Emitter? is it ok? it is the same in all of the channels transistors)

    The truth is that I have an general electrical knowledge but I never touch in hands and never really fixed things. so I dont know what is the next step.
    How can I check and find the bad part in my amp?

    Thanks a lot for any help or advice, even a link to some guide will be helpful.
    Best wishes,
    Alon
     
  2. Alon Perelmuter

    Thread Starter New Member

    Apr 23, 2016
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    0
  3. Dodgydave

    Distinguished Member

    Jun 22, 2012
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    Check pages 17,18 of datasheet, check the six channels have all the same sound going in and out,.
     
  4. Alon Perelmuter

    Thread Starter New Member

    Apr 23, 2016
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    What do you mean to to check the sound?
     
  5. wayneh

    Expert

    Sep 9, 2010
    12,103
    3,038
    I'm assuming this is the DC voltage reported by your multimeter? Your transistors, in normal operation will be passing audio-frequency sine waves. They will be alternately conducting and not conducting. The fact that your meter reads that as a small DC voltage is not surprising. But I don't think it's useful diagnostic information unless the schematic provides a reading to check it against.
     
  6. #12

    Expert

    Nov 30, 2010
    16,278
    6,789
    It's an audio amplifier. That means it makes speakers work. The speakers make sound.
    Connect the same input to all the channels and listen to find out if all the speakers are making sound.
     
  7. Alon Perelmuter

    Thread Starter New Member

    Apr 23, 2016
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    All the channels are working good.. I mentioned that the problem is only in the Front Right channel...

    Anyway, I found out that the B1560 transistor of the right channel is having very bad soldering, and the base of the transistor was not connected strong, so i tried to re-assemble this and something happened after connecting the power supply, I think I touched something with a screw, and now it turn to PROTECT MODE and then it tuyrn of all the time... I think now something maybe burned or something...
    So now I need help to understand how to figure this protect mode...
    Thanks and sorry for the newbie questions
     
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