Pioneer SX-980 Channel drop....distort...low volume

Discussion in 'Pioneer Audio' started by Mark Davis, Nov 7, 2018.

  1. Mark Davis

    Mark Davis Active Member

    Messages:
    136
    Location:
    Richmond, Virginia
    I have a Pioneer receiver that I recently got in pretty Mint condition.

    I recently set it up and started listening. I noticed occasionally it will play fine on FM and then the left channel will drop out.

    I tried plugging in my IPOD with a nice gold plated Aux cable. Same thing was happening.

    Yesterday I had the IPOD plug in everything was working fine.

    I went to plug in the power adapter for the IPOD and when I did the channel dropped immediately.

    Would you think this would be a grounding issue?????

    The stereos from the 70's only had a 2 prong plug on them.

    I still have other troubleshooting to do but thought I would ask in advance.

    Any input appreciated.

    Thanks in Advance!
     

     

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  2. Punker X

    Punker X Moderator Moderator Subscriber

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    Moving this to the Pioneer forum since it has nothing to do with the FM section. Also with the recommendation you look up some threads on cleaning all the controls in receiver.
     
  3. dcgibby

    dcgibby Member

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  4. merlynski

    merlynski Curmudgeon Electronicist Subscriber

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  5. Mark Davis

    Mark Davis Active Member

    Messages:
    136
    Location:
    Richmond, Virginia
    Does the Protection relay affect both channels or just one.

    I am having one channel drop and very low distortion out of the channel that dropped.
     
  6. Watthour

    Watthour Electron Rancher - JS3600

    The contacts in the relay can affect a single channel.

    Repair can be as easy are removing the relay cover and running a burnishing board between the contacts. However, while that may sound easy, accessing the relay and removing the cover can be a challenge. It is accessible from the bottom side of the unit.

    (Photo courtesy sawdust)
    [​IMG]
     
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  7. zebulon1

    zebulon1 Building a new bench. Finally! Subscriber

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    How about checking pin 8 on the protection board for ACv's when the receiver is operating with music?
    Wet finger the input to the left amp board pin 6? See if you hear a hum from the left speaker. Or touch the left jumper with your finger and check for hum.
    Don't forget to look at the jumpers for corrosion.
     
    Last edited: Nov 14, 2018
  8. Mark Davis

    Mark Davis Active Member

    Messages:
    136
    Location:
    Richmond, Virginia
    Does anyone have directions on how to replace theis protection relay?

    Is it soldered on the bottom?

    I see the part number is 653-MY2-02-DC48.

    Mine looks totally different I guess it could be original.

    Do I just release the plastic clips holding the board on to get to the back side?

    Any other troubleshooting tips to determine if it is the relay?

    20181114_164546.jpg
     
  9. merlynski

    merlynski Curmudgeon Electronicist Subscriber

    Messages:
    643
    Location:
    High Plains, Eastern Colorado
    Is it soldered on the bottom? YES

    I see the part number is 653-MY2-02-DC48. YES

    Mine looks totally different I guess it could be original. I think so too.

    Do I just release the plastic clips holding the board on to get to the back side? YES

    Any other troubleshooting tips to determine if it is the relay?

    Once you get the board loose from the chassis you can try bypassing it, but that puts your output transistors and speakers at risk. If I am already in that deep I would just replace it. They are a 'usual suspect' for this kind of problem, along with all the other switch contacts in the signal path. I would try Deoxit on the front panel switches and pots, and exercise them repeatedly before replacing the relay, though. They are 'usual suspects' as well. If you can get the cover off the relay you can burnish the contacts and/or Deoxit them as well. As Watthour says in post 6 that can be a challenge.
     
  10. Mark Davis

    Mark Davis Active Member

    Messages:
    136
    Location:
    Richmond, Virginia
    I took the tape off around the relay. What are those two squares on each side?

    I was going to try and get the cover off to look at the contacts. How do you do that?

    20181130_111407.jpg
     
  11. rcs16

    rcs16 Super Member

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    Location:
    Baldwin, Ontario, Canada
    The tape around the relay is a sign that someone was in there attempting to repair the relay, broke the cover and taped it back together.
    Yes those are nylon pcb standaoffs/restrainers, use your needle nose pliers to squeeze the tabs gently, they lock the pcb.
    So the relay is toast, un-solder it and replace it.
    I am not sure what those 2 rectangular devices are, I do not see them in the service manual,p68,69. Do they have any writing on them?
    Take a pic of the solder side, to see what they connect to.
    Might want to replace those ecaps while you are at it.
     

     

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  12. Mark Davis

    Mark Davis Active Member

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    Location:
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    No writing and they don't look to be attached to anything. The cover will not come off the relay so I think the tape was there originally.

    See post #8 above before I took the tape off. What are the ECAPS? 20181130_120533.jpg
     
  13. mattsd

    mattsd AK Subscriber Subscriber

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    Those are magnets, they are placed to help extinguish DC arcs between the contacts when they engage and help extend the life of them. If you replace the relay, make sure you put them on the new relay. Place them in line with the contacts inside, a dab of superglue will mount them in place.
     
  14. merlynski

    merlynski Curmudgeon Electronicist Subscriber

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    Location:
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    The easy way to get the cover off is to unsolder and remove the relay and then gently pry away the edges that are over the retaining nubs on the relay body and slip it off. They do not come off easily while the relay is still soldered into the PCB.

    The rectangular devices are probably magnets that are taped to the relay cover. The magnetic field bends the electric arc that forms when the contacts open to quench it more quickly. Makes the protection relay and protection process work better, faster, and more reliably. They were probably attached to the relay by Pioneer, or their relay vendor, before it was installed, and are part of the relay's Pioneer part sub-assembly number and thus may not appear on the BOM. If you replace the relay see if the old cover will fit onto the new relay thus retaining the magnets functionality, or move them to the new relay cover.
    ECAPS are (the blue) electrolytic capacitors, which have a specific polarity +/- and must not be installed backwards.
     
  15. merlynski

    merlynski Curmudgeon Electronicist Subscriber

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    Location:
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    Beat me to it by seconds :D.
     
  16. rcs16

    rcs16 Super Member

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    4,166
    Location:
    Baldwin, Ontario, Canada
    Very interesting, I learnt something today :)
    I guess they started doing this in the SX-x80 series receivers. Never seen it done in previous models. is it because Pioneer switched relay vendors (cost reductions)? used lower capacity relays? or just something they clued into at the time?
    Now I have to determine if I should use magnets on the new relays I used for the new SX-1980 PS pcb I designed, Umm, I guess it would not hurt? However I did use relays with 16A contact ratings rated for large surge currents such as in uWave ovens & motors.
    I see in pics that member "turbotx" posted of his SX-1980 PS design, he did not transfer the magnets onto his new SX-1980 PS relays. probably did not clue in as I have just done, good timing for me guys = thanks

    Rick
     
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  17. Mark Davis

    Mark Davis Active Member

    Messages:
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    Location:
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    I cleaned the balance knobs and what I could get to without tearing the whole thing apart.

    Been listening all afternoon. No channel drop or distortion.

    Hopefully I will not have to replace the relay.

    Thanks for all the input.
     
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  18. rcs16

    rcs16 Super Member

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    4,166
    Location:
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    fader lube F5 for pots, since they need lube
     
  19. Mark Davis

    Mark Davis Active Member

    Messages:
    136
    Location:
    Richmond, Virginia
    Yes I did that.
     
  20. merlynski

    merlynski Curmudgeon Electronicist Subscriber

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    That is one of the things I REALLY like about AK, hardly a day goes by that I don't learn something new, or 'unlearn' something I was wrong about.:biggrin:
    Thanks to all here who participate! :angel:
    merlyn
     

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