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Pioneer SX-750 phono problem

Discussion in 'Pioneer Audio' started by igor65, Jul 15, 2017.

  1. igor65

    igor65 New Member

    Messages:
    6
    Location:
    Ukraine
    Hello, i'm new here, first post: i'm from Ukraine and i apologize for my bad english: i hope someone will help me in fixing this amazing receiver When you turn on the phono, the speakers show a splash and cracks, lights up on the flash scale and the trip relay (phono transistor board)

    С ув Igor65
     
  2. zebulon1

    zebulon1 Into Phase Linear's lately Subscriber

    Messages:
    3,774
    Location:
    Las Vegas Nevada
    Is it popping and cracking when using the other inputs like the tuner, aux or tape monitor?
    Is it in both channels? Left and right speakers? Turn the "Balance" knob from side to side and hear if it is popping on both channels.
    Cleaning the selection switches is the first order.
    The phono EQ uses an op amp IC, TA7136. I can see one causing an issue on one channel, but both:dunno:
    Start with a good cleaning of the phono select switch. A good contact cleaner followed by a switch lubricant.
     
  3. igor65

    igor65 New Member

    Messages:
    6
    Location:
    Ukraine
    PROBLEMS ONLY WITH PHONO. BALANCE-RIGHT BURNER REPRODUCES SOUND, BALANCE-LEFT DOES NOT REPRODUCE SOUND, MAKES PROTECTION -RELLE
     
  4. zebulon1

    zebulon1 Into Phase Linear's lately Subscriber

    Messages:
    3,774
    Location:
    Las Vegas Nevada
    Good. You narrowed it down.
    It's probably the IC.
    You could swap the IC's and see if the popping travels to the other channel.
    Start looking for a TA7136, IC.
    Also check the voltage into the EQ. Make sure the supply is correct.
     
    Last edited: Jul 15, 2017
  5. igor65

    igor65 New Member

    Messages:
    6
    Location:
    Ukraine
    No popping travels to the other channel.
    Sx-750 in photo does not have TA7136
     
  6. zebulon1

    zebulon1 Into Phase Linear's lately Subscriber

    Messages:
    3,774
    Location:
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    :dunno:

    Their on the main board in the back. Near the back plate. Behind the tuners VC.
     
    Last edited: Jul 15, 2017
  7. igor65

    igor65 New Member

    Messages:
    6
    Location:
    Ukraine
    thanks for the help,I will clean the dust, and after that I will check these two boards :):beerchug:
     

    Attached Files:

  8. zebulon1

    zebulon1 Into Phase Linear's lately Subscriber

    Messages:
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    Location:
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    That's them.
    Interesting, they are boards.
    The boards may contain transistors which will make the repair much easier.
     
  9. tsd71

    tsd71 Gittin Some Head!

    Messages:
    2,598
    Location:
    New Jersey
    Seen those boards many times, rebuild both of them with new caps and transistors and you should be ok. I desolder the flexible cables from the bottom of the unit, it makes taking these out and repairing them a hell of a lot easier.
    The transistors can be replaced with 3 KSA992, and 1 KSC1845.
     

    Attached Files:

    Last edited: Jul 17, 2017
  10. igor65

    igor65 New Member

    Messages:
    6
    Location:
    Ukraine
    Thanks you !I am engaged in search new caps and transistors,
     
  11. zebulon1

    zebulon1 Into Phase Linear's lately Subscriber

    Messages:
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    Location:
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    The scat shows the IC's but when looking at images on line I see a few different types of boards. The 750 does use the IC's in the tone control board.
     
  12. paultlaw

    paultlaw AK Subscriber Subscriber

    Messages:
    180
    The one i worked on had those 2 boards instead of the IC.
    The service manual do have the schematics a shown above. Be careful desoldering the flexible cables from the bottom of the unit, the covering completely came off mine and i had to get creative to get the boards back in the unit as i could not get them parallel again i.e. they were gonna short out cos they were touching.
    If you are nifty and could solder them in situ i would go for that, if not go for removal of the boards but be very careful.
     
  13. igor65

    igor65 New Member

    Messages:
    6
    Location:
    Ukraine
    And I understand, I will be very careful:idea:
     

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