Another Pioneer SX 1250 restoration

Discussion in 'Pioneer Audio' started by boris_CH, Jul 17, 2017.

  1. boris_CH

    boris_CH New Member

    Messages:
    42
    Location:
    Switzerland
    Hi folks,

    of course I paid too much, but I wanted to have that unit. Faceplate is more or less ok, the usual scratches and bumps, but nothing extreme. Lights are all burning, but no sound. Neither via headphone, nor via speakers. If I am not wrong, I can't hear the relay clicking at the start, so maybe that's all? Fingers crossed! By the way, does anybody have an idea what the replacement type for the relais is? The service manual is saying ASR-015, may I use the OMRON MY4-02-DC24?

    Thanks, Boris
    IMG_0215.JPG
     
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  2. Robisme

    Robisme Sansui Enthusiast Subscriber

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    Doubt it's the relay.

    Didn't look at the service manual. Is that the soft start relay? Have you checked the soft start resistor? And blown fuses?

    You should get two relay clicks. One about a second (or less) after power up (soft start) and one about 10 seconds after power up (speaker relay).

    Rob
     
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  3. boris_CH

    boris_CH New Member

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    42
    Location:
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    Hey Rob, did not yet check anything, just made a lot of cleaning. Regarding the relay clicks there is nothing to hear. Just the lights turn on, but nothing more. I will have a closer look at the service manual...
     
  4. w1jim

    w1jim I can fix it but good... Subscriber

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    Step one - check the voltages on the power supply regulator PCB.
    It's unlikely the relay is your culprit - though it could be the transistor that drives the relay.

    Don't do a complete recap until you've got it working - otherwise you could have a prolonged restoration process.
     
  5. SaturationPt

    SaturationPt AK Subscriber Subscriber

    Messages:
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    Location:
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    I agree, unlikely (but possible) that it is the relay, time to do some checking first.

    The Pioneer forum on this website there are many SX-1250 threads, and lots of "no sound" posting and troubleshooting. My suggestion is to start there (it is most likely a voltage / PS issue keeping it in protection as stated above).
     
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  6. boris_CH

    boris_CH New Member

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    Location:
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    Thanks guys, I will have a look at the Pioneer forum here...
     
  7. satellite65

    satellite65 AK Subscriber Subscriber

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    Do you have jumpers from preamp out to power amp in?
     
  8. boris_CH

    boris_CH New Member

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    Yes - sure ;)
     
  9. KingBubba

    KingBubba "Too Much Stuff" Subscriber

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    ASR-015 is an I.D. # not the part model #.
     
  10. Robisme

    Robisme Sansui Enthusiast Subscriber

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    He is not getting the soft start relay to click. Check the soft start resistor and output transistors for shorts if it's bad.

    Edit: If the microtemp fuse, soft start resistor, or soft start relay are bad, you wont have lights.

    Are you 100% you don't get the soft start relay right after powering it up?

    Rob
     
    Last edited: Jul 17, 2017
  11. boris_CH

    boris_CH New Member

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    Location:
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    Not 100% sure. I hear a click when switching off, but nothing when switching on... or my ears are already bad... ;)
     
  12. Robisme

    Robisme Sansui Enthusiast Subscriber

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    Well, if you get lights, the soft start circuit is not the problem. So now you need to find why it's in protection.

    Do a search for SX-1250 in protection, and you should be able to find posts by MarkTheFixer that will help.

    Rob
     
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  13. boris_CH

    boris_CH New Member

    Messages:
    42
    Location:
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    Ok, checked the electrolyt capacitors on the protection board- all still in specs.
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    IMG_0422.JPG
    I could be wrong, but the relay looks like someone already tried to open it (sorry pics not that sharp...) - not yet checked the diodes...
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  14. boris_CH

    boris_CH New Member

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    Location:
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    Hi there, could a moderator maybe move this thread in the Pioneer section? Thanks a lot!
     
  15. tsd71

    tsd71 RIP Tom Petty Subscriber

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    On the 1250 you should hear a relay click soon after you flip the power switch (soft start), after that maybe 3-5 seconds later another click from the protection relay. If you do not hear either I suggest you do not power up again unless you have a working dim bulb tester, search on here and you will find how to easily make one for yourself. Once on a 75-100 watt DBT you need to take measurements with a digital multimeter from the stabilizer, next to the big black caps on the right side from the front, then from the protection board next to the big black caps from the left side(the one with the relay). The 1250 is not a beginners unit and there are a mountain full of threads on how to attack a 1250. If you need help keep posting and upload some pics so we can see whats going on. Also pull off the bottom cover and see if the big caps are leaking on the inside, a common problem with the 1250.
    It's probably not a capacitor issue on the protection board, I have done lots of 1250's and the Achilles heel is the stabilizer board, it gets very hot and fries transistors, pull that board and visually check it. Check out the schematic below, it will help you.
     

    Attached Files:

    Last edited: Jul 24, 2017
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  16. boris_CH

    boris_CH New Member

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    42
    Location:
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    Thanks for the hints. The DBT should be built quite easy. Already removed the bottom cover and checked the big caps. They look fine. I will have a look on the stabilizer board tomorrow.
     
  17. Eastham

    Eastham More Class A than ever! Subscriber

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    Is it just me or do the contacts in that relay seem misaligned? Also, I'd check the output transistors for shorts.
     
  18. boris_CH

    boris_CH New Member

    Messages:
    42
    Location:
    Switzerland
    Maybe I should add, that the previous owner said, that the unit used to work and then started with some temporary breaks - of course I don't know if that's the truth...
     
  19. w1jim

    w1jim I can fix it but good... Subscriber

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    "Worked when new" - a popular claim of the seller.

    I'd check the transistors on the protection board.
     
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  20. SaturationPt

    SaturationPt AK Subscriber Subscriber

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    965
    Location:
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    Don't bother reinstalling that relay, if it comes out it should stay out, spend the $13 for a new one (they all fail eventually).

    Looks like I used an OMRON MY402DC24.
     
    Last edited: Jul 25, 2017
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