4270 doesn't power up

Discussion in 'Marantz Audio' started by billinchile, Sep 10, 2017.

  1. billinchile

    billinchile Member

    Messages:
    50
    Location:
    Paris, France
    This receiver had a similar problem over 6 months ago and was "repaired" by a local tech. Please note that here in Brazil it's very difficult to locate somebody competent to work on these vintage units, and I'm not sure the guy I found is one of them. At that time, he merely replaced a couple of caps on the power supply board. Due to travel, I only used the receiver a couple of times since them. The other day it again wouldn't power up.
    Something that strikes me as curious is the fact that when the unit is plugged into the wall socket (but without the front panel power switch activated) , I get voltage at both rear AC outlets (127VAC at the "Unswitched" one and 122VAC at the "Switched" one). Might this indicate some kind of problem with the front panel power switch? Shouldn't I be measuring 0VAC at the "Switched" rear outlet?
     
    Last edited: Sep 10, 2017
  2. mbz

    mbz AK Subscriber Subscriber

    Messages:
    1,103
    Location:
    Melbourne, Victoria
    Correct, UNSWITCHED outlet should be at mains voltage, SWITCHED outlet should be a zero volts.
     
  3. wlhd1610

    wlhd1610 Penny and her new friend Subscriber

    Messages:
    2,180
    Location:
    upstate new york
    Could be the sensitivity of your meter.
    For starters...
    Plug a 100 watt table lamp into each outlet and see what happens.

    Bob
     
  4. mbz

    mbz AK Subscriber Subscriber

    Messages:
    1,103
    Location:
    Melbourne, Victoria
    OK, so you have a problematic power switch, however that probably does not
    explain the failed power ON.

    Suggest turn amp on then measure VAC at SWITCHED outlet, if it's still 120VAC
    then you need to look elsewhere, next step would be the power supply. However
    if the SWITCHED outlet is lower than 80-100VAC(?) then the power on switch needs
    to be replaced.

    Do you have the skills/tools/time to perform basic troubleshooting, if power switch is
    ok the next steps are
    - check power supply voltages
    - check solder joints
    - check for damaged/stressed components
    ...
     
  5. billinchile

    billinchile Member

    Messages:
    50
    Location:
    Paris, France
    Thanks very much for your replies. I'm a continent away from the receiver right now, but I'll be back in Brazil the 2nd week of October. Since I'm here in the U.S., I bought a new power switch for my 4270, just in case I need to replace the original one. I also purchased a replacement power supply for it that looks very clean and, according to the seller, was functioning normally when it was pulled. I'll be taking these back to Brazil. While I'm at it, I would much appreciate receiving any suggestions of components (such as capacitors) that I could buy in the U.S. that I might need in order to bring my 4270 back to life. High quality capacitors are sometimes very hard to find (and when found, are very expensive) in Brazil. Two things that I'm definitely taking back are desoldering braid and DeOxit, products that apparently no techs in Brazil have heard of. Thanks.
     
    Last edited: Sep 19, 2017

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