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IndustryArena Forum > MetalWorking Machines > Okuma > Okuma VAC 3 D11 Spindle Drive Not Powering Up
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  1. #1
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    Okuma VAC 3 D11 Spindle Drive Not Powering Up

    We recently purchased a MC-50A Machining Center that has not run in several years. I knew that there were issues with the VAC 3 drive when I purchased the machine. I have recently got the machine powered up. When I put power on the VAC 3 drive the fan on the spindle motor starts running but I get no power indicator light on on the front panel. In going through the trouble shooting manual they say to check the fuses. The 5 fuses on the top of the middle board are good. The 12 HM fuses down the right side of the front board are good. The two fuses on the bottom of the middle board are good. But I can not find the MP50 or warning fuse that they said I should check. The diagram on the maintenance manual says it should be above and to the right of the DIP switches but I am not finding anything. Can anyone give me any clues? I have attached pictures of my drive.
    Thanks in advance for any help or ideas.
    Attached Thumbnails Attached Thumbnails 20210712_173647.jpg   20210712_173559.jpg   20210712_173502.jpg  

  2. #2
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    Re: Okuma VAC 3 D11 Spindle Drive Not Powering Up

    yep, no pictures attached on either of the posts for your problem.
    Cheers
    Brian.

  3. #3
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    Re: Okuma VAC 3 D11 Spindle Drive Not Powering Up

    Well, let me try this again. I thought that I had added the pictures to my posts.
    Thanks,
    David
    Attachment 466610Attachment 466612Attachment 466614Attachment 466616Attachment 466618Attachment 466620Attachment 466622Attachment 466624

  4. #4
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    Re: Okuma VAC 3 D11 Spindle Drive Not Powering Up

    higher quality picture required. The area to look for the "Warning Fuse" is marked by red elipse
    Click image for larger version. 

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  5. #5
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    Re: Okuma VAC 3 D11 Spindle Drive Not Powering Up

    Algirdas,
    Here are a couple of close up pictures of the area that you circled. I know that my eyes are getting bad but I just don't see a fuse in that area. I hope you can shed some light on it for me.
    Thanks,
    David
    Attachment 466646Attachment 466648

  6. #6
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    Re: Okuma VAC 3 D11 Spindle Drive Not Powering Up

    1. Check other side of the board. Not likely ...
    2. Attachment 466704 check:
    SF3B41 looks like transistor, but I see no more transistors marked "SF ..." check how it is connected. If only 2 leads used, maybe it is kind a fuse.
    the big diode next to C84. The diode can serve as a fuse as well.
    0,2ohm check the continuity of this resistor. No need to dismount. It should be bigger ( power dissipation capacity ) in my opinion.
    3. Clean the board. Rusty brown sediment can be conductive enough to cause the fail.
    looks like there is power supply part - voltage stabilizers - on this corner. Check if the mains voltage is reaching that part of the board, check all power transistors.
    4. When the board is clean. Look for evident sign of heat on resistors. Crack on semiconductors body.

  7. #7
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    Re: Okuma VAC 3 D11 Spindle Drive Not Powering Up

    Algirdas,
    Looking closer at the components that you suggested. The SF3B41 is a thyristor. The C84 is a diode and it checked continuity in one direction and open in the other so I am going to assume that it is good.
    I guess I am going to have to send it in to a repair company and see if they can bring it back to life. Thanks for your suggestions.
    Thanks,
    David

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