Problem with my SX 780

Discussion in 'Pioneer Audio' started by rediffusion, Feb 17, 2017.

  1. rediffusion

    rediffusion New Member

    Messages:
    5
    Location:
    Fairfield, CT
    Hi,

    This is my first post here. I bought a Pioneer SX 780 receiver back in 2013 and it’s been working well until recently. Over the last few weeks when I turn it on everything lights up but I can’t get any sound out of it - radio, turntable , aux plus I can't get any sound from the headphones. There’s obviously power going to it but for some reason there’s no sound. The speaker cables are all connected correctly. When I used to turn it on, the lights came on then after a second or two there would be a click and the audio would play. This doesn’t happen anymore.

    I asked this question at stevehoffman.tv and was directed to this forum.

    Does anybody know what the problem could be? It has been suggested that it might be a delay/protection relay problem.

    Strangely, a week or two after this started happening I had to turn the power off in my house for 20 minutes. When I turned it back on the stereo started playing as normal. It worked for the rest of the day but when I turned it on the next day – nothing.

    I live in Fairfield, CT and was wondering if anybody could recommend a place to get this serviced that's not too far away from me.

    Thanks for taking the time to read. Any advice would be gratefully received.

    R ;)

    [​IMG]
     
  2. glen65

    glen65 Member

    Messages:
    4,279
    Location:
    Richland county, Ohio
    Maybe, or an amplifier issue causing it to go into protection. However some things I would want to check for are bad solder joints and power supply issues.
     
  3. rediffusion

    rediffusion New Member

    Messages:
    5
    Location:
    Fairfield, CT
    Thanks for the reply, Glen.

    I'm not really technically minded when it comes to electronics. What's the best way to find a reputable person/company to take a look at it? Any tips?
     
  4. bberkom

    bberkom AK Subscriber Subscriber

    Messages:
    597
    Location:
    Nashville, TN
    I'd post your location in your profile if you want someone else to have a look, and I bet you'll have some AKers nearby who could help. Or someone can direct you to someone local to you.
     
    rediffusion likes this.
  5. rediffusion

    rediffusion New Member

    Messages:
    5
    Location:
    Fairfield, CT
    Great – will do. Thanks for the reply.
     
  6. rediffusion

    rediffusion New Member

    Messages:
    5
    Location:
    Fairfield, CT
    I hope it's OK to bump this thread. Can anybody recommend a reputable person/company to take a look at my SX760 within a reasonable distance from Fairfield, CT? Failing that, what's the best way to find somebody that will do a decent job?

    Many thanks in advance.
     
  7. larryderouin

    larryderouin Do I get Food, Med's, or more gear this Month? Subscriber

    Messages:
    18,889
    Location:
    Glen Burnie Md.
    URBAN RADIO near West Hartford.
     
  8. rediffusion

    rediffusion New Member

    Messages:
    5
    Location:
    Fairfield, CT
    Thanks, @larryderouin
     
  9. rickygallagh

    rickygallagh New Member

    Messages:
    34
    Bumping thread. Same Problem, everything lights up, tuner vu also working. No sound and no clicking.

    As another post suggested, I checked Darlington packs on 200v dc with the following results

    Left Pac Right Pac

    1 +19 1 -40.4
    2 -41.3 2 -41.5
    3 -41.3 3 -39.2
    8 + 41.6 8 -39.3
    9 +41.4 9 +41.4
    10 +21.8 10 -39.5

    Also checked .22 ohm resistors at pins 3-5 and 6-8 and one is bad on left.

    Should I order a like resistor .22 ohm not sure about watts is 5 o.k.?

    Thank you for any help!
     
  10. zebulon1

    zebulon1 Into Phase Linear's lately Subscriber

    Messages:
    3,660
    Location:
    Las Vegas Nevada
    Did you remove one leg and test the resistor(s)?
    You are on the right track.
    .22 ohm 5 watt. Replace all four.
    Get the resistors sorted and perform the DC Balance check.
    It might just come around.

    The right channel is good.
     
  11. rickygallagh

    rickygallagh New Member

    Messages:
    34
    Thank you for the help.

    I did not remove a leg of the resistors, just an ohms meter across the two legs and one resistor is infinite or "ol " on my meter which I guess it means it is open.

    Guess I will order the resistors off eBay
     
    Last edited: Apr 15, 2017
  12. zebulon1

    zebulon1 Into Phase Linear's lately Subscriber

    Messages:
    3,660
    Location:
    Las Vegas Nevada
    I have a ton of these:
    Mouser:
    588-TUW5JR20E, 0.20 OHM 5 WATT Wirewround. Through Hole.
    They should work fine.
    I can send four if you wish.
    PM me if interested.

    DSC03912.JPG
     
  13. deltalight

    deltalight AK Subscriber Subscriber

    Messages:
    138
    Location:
    Minneapolis
    The output thick film IC associated with the open emitter resistor is gone. Replacement is cheap and easy if you get a genuine part.
    Don't think any of it will last without a restoration. After 40-years, it won't last.
     
  14. rickygallagh

    rickygallagh New Member

    Messages:
    34

    Help me understand, is there a certain IC thats needs replacement also?
     
  15. zebulon1

    zebulon1 Into Phase Linear's lately Subscriber

    Messages:
    3,660
    Location:
    Las Vegas Nevada
    The voltages are almost there, minus the open emitter resistor on one side. I think the modules are fine. Once the resistor(s) is replaced we can see if it will operate with the correct voltages.
    If the module voltages are not behaving then a module is needed. Either way the resistor(s) have to be replaced. No harm done.
    Like I said I think the set will respond favorably.
     
  16. rickygallagh

    rickygallagh New Member

    Messages:
    34
     
  17. rickygallagh

    rickygallagh New Member

    Messages:
    34
    Readings before( left column) and after( right column) i replaced resistors, hopefully, correctly!

    L R
    1 +19 +18 1 -40.4 -.01
    2 -41.3 -41 2 -41.5 -41
    3 -41.3 -41 3 -39.2 -0
    8 +41.6 -41 8 -39.3 -0
    9 +41.4 +41 9 +41.4 +41
    10 +21.8 +21 10 -39.5 + 01
     
  18. rickygallagh

    rickygallagh New Member

    Messages:
    34
    L Power pack
    Before
    Pin 1 + 19 After 1 +18
    2 -41.3 2 -41
    3 -41.3 3-41
    8 + 41.6 8 -41
    9 +41.4 9 +41
    10 + 21.8 10 +21

    Right Power Pack
    1 -40.4 1-.01
    2 -41.5 2 -41
    3 -39.2 3 0
    8 -39.3 8 0
    9 + 41.4 9 +41
    10 -39.5 10 +01
     
  19. zebulon1

    zebulon1 Into Phase Linear's lately Subscriber

    Messages:
    3,660
    Location:
    Las Vegas Nevada
    I really messed this up. I don't what I was looking at but the packs are toast.
    The voltages at pins 3 and 8 should be very near zero (0v's).
    Both packs shorted is uncommon but they are.
    Your first readings showed it.

    Sorry I missed that.

    The readings show like the pack is not even there or soldered in. The left pack has a slight voltage change.
    I have one good pack here if you want it I'll send it. You'll have to scrounge for another one.
     
  20. rickygallagh

    rickygallagh New Member

    Messages:
    34

    I was suspecting the packs, I got a couple off eBay, for an SX-1000 that are the same numbers, that I can use.
     

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