Marantz SR840 - troubleshooting assist needed

Discussion in 'Marantz Audio' started by wd409, Dec 11, 2009.

  1. wd409

    wd409 Super Member

    Please forgive my double post, I forgot there was a specifically marantz section on here and do not know how to delete the one from vintage audio.
    Maybe a mod can delete that one for me?

    This unit had a broken power switch which I went ahead and replaced with a confirmed working one, but it still wont gimme my sweet marantz sound

    when I plug it in it lights up like you see in the picture, its unresponsive though to any button mashing exercise I go through. It makes me think its been hit by lightning but i see no burn marks or smell anything burned, so I need some help here.

    unless there is some special way to turn this thing on that I dont know about, im guessing it has a short somewhere.

    thanks in advance.

  2. dspear99ca

    dspear99ca Super Member

    Fried power switch + scrambled logic IC's = maybe you're right about lightning...

    Check the secondary regulated power supply voltages that feed the boards with IC's... the FM MPX, the input selector IC that takes input from the front-panel microswitches, the preamp and phono section. If you're lucky there's a voltage regulator that's bad and that's all it is.... it's possible a single 7805 or 7812 feeds all of the logic in the beast.
  3. wd409

    wd409 Super Member

    power switch wasnt fried, just broken. physically broken.

    its one of those little push button deals to take it out of standby and it was damaged.

    anyway, im gonna start checking things in a bit. I keep getting interrupted by the phone ringing, not that that is a bad thing, means someone wants to give me money.
  4. wd409

    wd409 Super Member

    does anyone have a tech sheet for this beasty?

    or, can tell me what the voltages of each wire coming out of the transformer should read at?

    I havnt started testing on it yet but I dont remember seeing the board marked yesterday with whats what.
  5. macman007

    macman007 Mcintosh..Made In USA

    I'd start with a good cleaning inside and out. Looks like it's seen some moisture in it's past. :thumbsdn:

    Then start cleaning all switches, buttons and ribbon cable connectors with deoxit. If it has a set of fins for manual dial tuning just blow it out, don't use cleaners just a soft brush and a little air pressure. I didn't notice if it had a manual tuning knob in your picture.

    A clean unit with good connections and clean switches and controls is much easier to diagnose than one in this units current state of cleanliness and corrosion.

    Might be as simple as a poor connection at one of those connector cables inside. Other will chime in here also. Look for a schematic online, Google can be helpful.

    A lot of schematics are available online for free if you look hard enough. We may have one in AK documents.

    May also be a logic issue if there was a voltage spike in it's history. :thumbsdn:

    Good Luck, it looks like it's going to be a fun project! :music:In the end it'll be worth it when your surfing the airwaves! :yes:

  6. The1thinker

    The1thinker New Member

    I have the SR 940. Did u try to pushing the FM button. That is how you would regularly turn it on.
  7. bktheking

    bktheking Gitter Done! Subscriber

    You're answering a 4 yr old post.
  8. vfd fan

    vfd fan Member

    [​IMG]i have qestion abaut am stereo module connector on tuner board

    :scratch2: were is exactly located:yes:
  9. PhilA

    PhilA Active Member

    I know it's a way old, dead thread, but I got the same result on mine when I put the ribbon cable into JP530 backwards. Stripe goes to pin 6 not pin 1, unlike all the other ribbons on the boards.

    Just in case someone else makes the same mistake, because this thread shows up in Google.

    Hope it helps someone

  10. vfd fan

    vfd fan Member

    hi-i am search am stereeo module-can your help me

    Attached Files:

  11. ivantowerz

    ivantowerz New Member

    marantz sr840 found recently

    I recently got this receiver from a hope chest second hand store for 5 dollhairs. Left side cuts out at low volume and balance fader is scratchy. There are no pots to clean so what do I look for to clean. Also, how do I remove the faceplate without breaking the timer switch dial?
  12. ivantowerz

    ivantowerz New Member

    Figured it out, I desoldered the speaker relay and cleaned them with 90% alcohol. Resoldered and it fixed the problem

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