1550 pops on shut off

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

  1. Electone

    Electone Well-Known Member

    Messages:
    671
    Location:
    London, Ontario, Canada
    A friend of mine brought over his 1550 to check over. It sends a nasty pop through the speakers when you shut it off with the speaker a or b button on. If you turn off the speakers and shut it off, no pop. I cleaned the main relay and set the offset to the proper 0V (it was way off at -160mV per channel). One thing I can't adjust is the idling current. The pots aren't doing anything and showing 0V all the time. They are supposed to be at 24mV. Is there anything else I should be checking?

    Thanks
     
  2. don philipe

    don philipe AK Subscriber Subscriber

    Messages:
    1,097
    Location:
    West plains mo
    I have two 2275's that pop when powered down,it's not a loud pop,I just hit the speaker button before powering down and learned to live with it.If you find a solution let me know.
     
  3. willyrover

    willyrover Super Member

    Messages:
    2,809
    Location:
    Hamilton
    For bias adjust, are you using the correct test points?

    Screen Shot 2017-03-19 at 2.51.38 PM.png


    For the pop on turn off, it sounds like the relay isn't releasing fast enough. The relay is supposed to open and prevent this pop from getting to the speaker. Once you have confirmed the relay itself is good isn't sticking mechanically, I would start by checking diodes, resistors, and capacitor values in this circuit.

    Screen Shot 2017-03-19 at 3.04.04 PM.png
     
    Last edited: Mar 19, 2017
    KutzlerTrans likes this.
  4. Electone

    Electone Well-Known Member

    Messages:
    671
    Location:
    London, Ontario, Canada
    Yes, definitely have the correct posts. J708+ J709- for R731. J710+ J711- for R732. I only get 0V and the pots do nothing. Going to check again. Had no problem setting the offset. I will measure some voltages on that board. Thank-you.
     

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