SX-5580 SX-1050 SMOKING HOT...ON POWER UP

Discussion in 'Pioneer Audio' started by r887661, Sep 10, 2017.

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  1. r887661

    r887661 AK Subscriber Subscriber

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    Location:
    Ludington, Michigan
    Took a while to get there but it stabilized at 1.986 kohm
     
  2. r887661

    r887661 AK Subscriber Subscriber

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    Location:
    Ludington, Michigan
    Here are pics of before (1153) and after (1156)...appreciate your interest...Ian
     

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  3. merlynski

    merlynski Curmudgeon Electronicist Subscriber

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    Location:
    High Plains, Eastern Colorado
    Pin 3 Almost 2K ohms shows it is not shorted directly, the rising resistance is probably the cap charging..
    There is a discrepancy in the measurements:
    C1+, Positive Rail: 1st test = 0v 2nd test = 0v and
    AWR-104 Pin 3: +0.943v
    Both should be the same, as the schematic shows them connected together.
    Check with ohmmeter for continuity from AWR-104 pin 3 to C1+ terminal, and AWH-047 pins 1 and 20, should be 0 ohms between all 4 points.
    Pictures look ok to me, maybe somebody else will see something I don't.
     
  4. r887661

    r887661 AK Subscriber Subscriber

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    OK friend, I'm just heading out to work so it will be a while before I respond...but it will be today. Thanks for hanging in there...Ian
     
  5. merlynski

    merlynski Curmudgeon Electronicist Subscriber

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    No problem, that's how it goes, AK fits in the spaces between what happens in real life! :thumbsup:
     
  6. r887661

    r887661 AK Subscriber Subscriber

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    Long day, pooped....probably not fresh enough to stick my hands in the old girl tonight (???) Will start early tomorrow...I have a day off :)
     
  7. merlynski

    merlynski Curmudgeon Electronicist Subscriber

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    Get some rest! :D
     
  8. r887661

    r887661 AK Subscriber Subscriber

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    Location:
    Ludington, Michigan
    OK, here I am...went through all the readings again as per your original direction. However, I had to make a basic assumption that C1 is closest to the transformer and C2 furthest away....Correct? I could not find a schematic that identified them.

    So, based on that assumption, these are the fresh readings with ground properly identified:

    DBT = Full Short
    S2 = No
    C2 -ve = -0.919
    C1 +ve = 0.000
    P3 = +0.936
    P5 = -0.941
    P6 = +2.700
    P7 = -2.760
    P8 = +0.916
    From AWH-047
    P4 = -0.003
    P17 = -0.110

    From your posting #63 it looks like I have C1 and C2 crossed....However AWH-047 P1 to P20 = 0.200ohm

    Standing by to help best I can...
     
  9. merlynski

    merlynski Curmudgeon Electronicist Subscriber

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    Location:
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    We need to trace some wires, you are showing a voltage difference between AWR-104 pin 3 (0.936) and C1 +ve. (0.000)This should not be possible as they are electrically the same point on the schematic.
    The two big filter caps are C1 and C2, one should have its negative post connected to the ground bar between them, the other should have its positive post connected to the ground bar.
    To ID C1 & C2: With power off and disconnect from DBT check resistance with meter from AWR-104 pin 3 to the big cap positive post that is Not connected to the ground bar, should show 0 ohms. This should be the other end of the brown wire connected to AWR-104 pin 3. If not 0 ohms physically follow the brown wire from AWR-104 pin3 to wherever it goes. Let me know
    EDIT: do not power up again until we get this sorted out, as it may damage your new caps if they are miswired (backwards).
     
    Last edited: Oct 8, 2017
  10. r887661

    r887661 AK Subscriber Subscriber

    Messages:
    97
    Location:
    Ludington, Michigan
    Caps are wired as you say, one has -ve to ground bar the other has +ve to ground bar.

    I changed the battery in my Fluke 116, changed the leads and tested, I get 0.1 to 0.2 ohm probes connected. So one probe on P3 to the +ve on one cap is 0.2ohm, the other positive is to ground.

    The brown wire from P3 goes to the +ve terminal where I measure 0.2ohm.

    I'm going to completely clean both sets of cable ends....
     
  11. deltalight

    deltalight AK Subscriber Subscriber

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    193
    Location:
    Minneapolis
    I had the same SX-1050 "overheating surge resistor" issue recently. The solution was:
    1) Repair blown LChan outputs
    2) Rebuild Power Supply Assembly-A (AWR-103)
    3) Rebuild Power Supply Assembly-B (AWR-104)
    4) Replace C1 (10uF 63v) on AWX-098

    When they outputs are blown, the short prevents C9, C10 (470uF 80v) on AWR-104 from developing the needed 76VDC on Pin6 which is then dropped to 48V via R2 on AWX-098 to power S2 SoftStart Relay. If original i.e. 40-yrs-old, C9, C10 are trash and won't hold a charge anyway. Even if the 72V on Pin6 is OK, if C1 on AWX-098 softstart assy is old and maybe shorted and won't hold a charge, S2 still won't close. Since S2 won't close within 500mS at turn-on, the surge current is continuously routed through R1 (3.3ohms 20W) and the 10A TCO (microtemp) will open as heating continues, forcing primary voltage shutoff. Fortunately on mine, I shut it off immediately after starting to seeing R1 overheat and burn the masking tape that thermally-couples the TCO close to R1. That saved me from having to install a replacement TCO. Everything became normal after rebuilding the above-mentioned assys. Billows of smoke! Scary when it first happened! :eek:

    Apologies to Mark as I've repeated what he already said in post #24 which I didn't see before this.
     
    Last edited: Oct 8, 2017
  12. r887661

    r887661 AK Subscriber Subscriber

    Messages:
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    Location:
    Ludington, Michigan
    I have a spare 104 and a spare 103
     
  13. merlynski

    merlynski Curmudgeon Electronicist Subscriber

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    I saw that from earlier posts. At this time I want to check the wiring . . .
     
  14. r887661

    r887661 AK Subscriber Subscriber

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    Location:
    Ludington, Michigan
    I'm with you...
     
  15. deltalight

    deltalight AK Subscriber Subscriber

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    Location:
    Minneapolis
    You shouldn't need a spare 103 or 104 unless the copper traces are so trashed out that restoration is next to impossible.
     
  16. merlynski

    merlynski Curmudgeon Electronicist Subscriber

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    128
    Location:
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    OK, as long as it is wired correctly the next steps are to test or replace components on boards and output transistors.
    Changing a whole board is a lot of work that may not do anything helpful.

    That is something that may be done in the field (or on board a ship) because component level testing and replacement cannot be done effectively there. Those boards are usually equipped with connectors that can be unplugged and re-connected.
    On vintage audio unwrapping and re-wrapping all those connections is not efficient because the wires break and the pins are not reusable unless you solder all the wires.
    It is more efficient to replace failed components.
     
  17. merlynski

    merlynski Curmudgeon Electronicist Subscriber

    Messages:
    128
    Location:
    High Plains, Eastern Colorado
  18. r887661

    r887661 AK Subscriber Subscriber

    Messages:
    97
    Location:
    Ludington, Michigan
    I inherited this 5580 with four spare boards, previous owner had been tring to fix it and I fear it was probably made worse.

    I appreciate all who are helping me out...we WILL get it done...I have no doubt... :)
     
  19. r887661

    r887661 AK Subscriber Subscriber

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    Location:
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    Should I get a list of components required on 103 and 104? I have moderate skills with a soldering iron and feel confident...
     
  20. merlynski

    merlynski Curmudgeon Electronicist Subscriber

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    128
    Location:
    High Plains, Eastern Colorado
    Transistor, diodes and capacitors: Yes, and replacements for the output transistors, Q23 - Q30 (at least 4 each of two different kinds, NPN and PNP)
    There are lists already made up if you search AK, markthefixer is usually the person with the best recent replacement BOMs.
    Also the transistors and caps on the AWM-090 Protection PCB, and the cap on the AWX-098 Surge Killer PCB.
    There are many threads on AK dealing with testing SX-1050's circuits that apply to your SX-5580, search for SX-1050.
    You may be tempted to salvage parts from your spare boards, resist that, especially for caps and transistors as new replacements are usually better quality. Current BOM threads will help deal with that. Resistors are usually ok if they don't look burnt and measure correctly out of the circuit. You may want to order a few extra of each small transistor as spares in case any are fried during rebuild/retesting.
    The most expensive parts will probably be the output transistors, the other parts are usually inexpensive. Shipping is what kills you on small orders of small parts,
    You will also need new mica insulators and heatsink paste when changing out the output transistors.
    Forgive me if I am repeating things you already know.

    EDIT: for clarity and completeness
     
    Last edited: Oct 9, 2017

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