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MX-1000, how bad did I mess it up?

Discussion in 'Yamaha' started by RayN, Oct 4, 2018.

  1. RayN

    RayN New Member

    Messages:
    14
    Location:
    Boise, Idaho
    I recently purchased an AS-IS MX-1000 from the bay for a project. Other than being very dirty and bent, along with some loose connections on the speaker outputs, it worked! I spent some time cleaning it and bending it back into shape, the last thing I needed to do was replace some of the bulbs for the meter. Unfortunately when I was putting the front meter assembly back on I temporarily removed the main power leads coming from the transformers for access to the connectors for the front panel. When I replaced them I accidentally installed one of them offset by one pin. Now the system won't power on, however, I saw no smoke and smelled nothing burning. I hear a relay kick when I press the power button but both the power and protection lamps are dark. Help! I feel like a complete idiot.

    The fuses seem fine so I suspect the power supply. I'm comfortable replacing parts and I have the schematic, just hoping someone can help me jumpstart the process.

    Thanks
     

     

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  2. rottalpha

    rottalpha Yamaholic Subscriber

    Messages:
    1,731
    Location:
    Middle of Crook County
    Make sure you have all wires correctly connected
    Check all fuses once more
    Find a DBT and use it to power up the unit
    Report back with the results
     
    RayN likes this.
  3. RayN

    RayN New Member

    Messages:
    14
    Location:
    Boise, Idaho
    Thanks, I discovered my mistake when it didn't power up and it's connected correctly now. I'll build a DBT tonight and definitely use it in the future. I'm just surprised that if it was a dead short that I didn't let any smoke out.
     
  4. Bob

    Bob AK Subscriber Subscriber

    Messages:
    2,147
    Location:
    West coast
    if you post the schematic and what pins were shifted (left or right) we suggest avenues of
    investigation.
     
  5. RayN

    RayN New Member

    Messages:
    14
    Location:
    Boise, Idaho
  6. Bob

    Bob AK Subscriber Subscriber

    Messages:
    2,147
    Location:
    West coast
    OK, pull the connector, and it seems the left side are the bridge rectifiers, I'd check them for shorts.

    then the right side are the transformer taps, again, check for shorts.

    put a dbt on the thing, measure the voltages on the right side - make sure they are AC active
    then try without the DBT, and no connector, the left side transformer taps are correctly
    supplying voltage.

    then with an enlarged copy draw the mistaken connections made and see what got across
    from the left side to right.

    then if you are absolutely certain that nothing is shorted, the measure the voltages at the
    bridge rectifier outputs. should be what the schematics call for to drive the various circuits.

    this is not a step by step but more of a process.
     

     

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  7. RayN

    RayN New Member

    Messages:
    14
    Location:
    Boise, Idaho


    Thank you, this is what I plan to do. My guess is I fried some or all of the diodes in the bridge rectifier which is why I'm not getting DC voltage to the power lamp. Ugh.
     
  8. rottalpha

    rottalpha Yamaholic Subscriber

    Messages:
    1,731
    Location:
    Middle of Crook County
    If no blip of a hearth beat, look for open traces as well.
     
  9. Bob

    Bob AK Subscriber Subscriber

    Messages:
    2,147
    Location:
    West coast
    check all fuses everywhere you see them.

    bridges are easily replaced, and even if you have the requisite power diodes, you can
    sub them in.

    I have found 'bridge" rectifiers to be sensitive in spite of their dragster specs. so having
    one blowup is OK since it will prevent cascading failures into the circuits they power.
     
  10. rottalpha

    rottalpha Yamaholic Subscriber

    Messages:
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    Location:
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    check F301 front left, at te top of the amp when you have the top cover off. Not one of the four fuses on the main board.
     
  11. rottalpha

    rottalpha Yamaholic Subscriber

    Messages:
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    Location:
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    I missed this when I read yout post. If F301 is OK, use a DBT to power up the amp and report back.
     

     

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  12. RayN

    RayN New Member

    Messages:
    14
    Location:
    Boise, Idaho
    Ha! It was F301! Strangely there's continuity between the posts on that fuse so I had originally tested it as good when it was installed. I'm back up and running, thank you all so much!!
     
  13. rottalpha

    rottalpha Yamaholic Subscriber

    Messages:
    1,731
    Location:
    Middle of Crook County
    :thumbsup:
     
  14. RayN

    RayN New Member

    Messages:
    14
    Location:
    Boise, Idaho
    I've noticed this amp goes into protection mode at medium to high volumes. It doesn't seem to be with one channel or the other. Any thoughts? I'm looking into a recap of at least the power supply area.
     
  15. rottalpha

    rottalpha Yamaholic Subscriber

    Messages:
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    Location:
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    yep, you need a recap ASAP
    Had one that did the same thing. After recap and a few cold solder joints repairs, it sang like a canary
     
  16. RayN

    RayN New Member

    Messages:
    14
    Location:
    Boise, Idaho
    Thanks, got a cap kit on order and I'll work my way through it.
     

     

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  17. rottalpha

    rottalpha Yamaholic Subscriber

    Messages:
    1,731
    Location:
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    you got a what???
     
  18. RayN

    RayN New Member

    Messages:
    14
    Location:
    Boise, Idaho
  19. rottalpha

    rottalpha Yamaholic Subscriber

    Messages:
    1,731
    Location:
    Middle of Crook County
    I did not see a list but it does seem reasonable and a legit place.
    you will most likely will not receive the correct 110V 820uf caps on the main board.

    you will also need the relays. Check your mail box for a list of parts you would need...give it a few mins
     
  20. amr2

    amr2 Well-Known Member

    Messages:
    515
    Could you share your list with me please? Thank you!
     

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