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  1. #1
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    Quick Question

    Once the board is built can you still check the 5v circuit? Right now I have issues with my board per my previous post. I have a near dead short between the main negative terminal and the +5v pad. It only has 1.5 ohm. Can someone with a fully built board just measure the resistance between your main negative terminal and the +5v pad? I need to know if this is normal or not?

  2. #2
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    Anyone?

    Thanks,

    Jason

  3. #3
    Community Moderator Al_The_Man's Avatar
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    In the absence of a schematic and support for the board, it comes down to reverse engineering usually being necessary!!
    Al.
    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.

  4. #4
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    I have had this board soldered up for about a year now and I am just now wiring up the power supply. I did check the 5 v test per the instructions before I stopped working on it. I can check tomorrow evening.

  5. #5
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    That would be fantastic,
    Thanks

  6. #6
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    I measure 512 ohms across the ground and 5V pad.

  7. #7
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    Yeah I only have 1ohm so that is an issue.

    Sent from my SPH-D710 using Tapatalk 2

  8. #8
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    Maybe a bad 5v regulator??

  9. #9
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    That was my thought. They got really hot, really fast with only 12v. I am in process of removing the regulators. I have already removed the left one and the middle one, but still have one more to remove. I just have to remove the LM-317HV. Hopefully that is where the problem is. Once i remove it, there should be no connection between the 5v pad and the neg terminal... I believe, if it is the problem. If not then i am in trouble, because i have no idea where to go from there.

    Sent from my SPH-D710 using Tapatalk 2

  10. #10
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    Well I am lost now. I removed all of the regulators and I still have the dead short on the 5v line. I don't know what part would have gone bad to cause the short. Nothing on the board looks damaged. I really need a diagram of the board or something. I am lost at this point.

  11. #11
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    Are you a member of Dave's Yahoo group? There used to be a pretty active group for the HCNC boards.
    A lazy man does it twice.

  12. #12
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    Yeah and i posted it there but nothing... Nearly no help. Dave is no where to be seen. I posted there 12 days ago.

    Thanks,

    Jason

  13. #13
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    He does expect you to read a lot. I like the product once up and running. I do remember the frustration of being new to all if this. Once I passed all of the electrical tests and hooked up my machine, a whole new education was needed to figure out what to do to make the machine move. Mach configurations, MDI, GCodes, Hotkeys. I still know nearly nothing.
    A lazy man does it twice.

  14. #14
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    I have read back to 2008. I have searched for the same problem and found one or two that are close. I have eleminated them as the problem. At this point i just have to start removing parts till the short goes away. I am having issues removing the chips. Without a desoldering station i dont think i can remove them. The lack of support for this product bothers me. Without a diagram of the board i can't find where the short is happening.

    Thanks,

    Jason

  15. #15
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    Ok i have narrowed down the short to the Y axis. I have a short to the Y vref pad. I have removed the chip between the x and y, the variable resistor, and both caps on the Y. The short is still there. I did a resistance check of the driver chip and it matches the others. Ahhh

    Sent from my SPH-D710 using Tapatalk 2

  16. #16
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    At least you are making progress in your diagnosis. Still no help on the yahoo site? I wish I could help, unfortunately with my advice you would
    likely chase more shorts ;-) Good luck and keep us updated on your progress and eventual solution.
    A lazy man does it twice.

  17. #17
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    I dont know if this will help, how accurate it is, or if it will be any help.

    But I found this in a post about modifying the board.

    John

  18. #18
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    Quote Originally Posted by lucas View Post
    That short on the Y Vref is a good indication.
    I would guess that the Y driver chip is shorted internally and pulls both the Vref and +5 down.
    You could compare the resistance of all chip pins with each other, if one or more pins of the Y chip is different then it's probably blown.

    To be sure you could cut the 5V pin of the chip or the PCB trace to that pin (do it in such a way that you can resolder them back) and then measure again.
    What supply did you use, you mentioned 42V IIRC, this may be on the limit.
    Ok, I have removed the y-axis driver chip. The resistance at the y-vref is no longer shorted. With chip removed I now have 20k ohm. So, the y chip was bad. I still have a short on the 5v line and I am suppose to 512 ohm. The 5v tab has two path ways, I am going to break one of them and start tracing in the other direction. I have made several things to help me trace it. I have some helpful photos on my photobucket page located HERE

  19. #19
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    512 ohm between 5V and ground is NOT a short, there could still be a too high load but I'm quite sure this could be OK.
    If you still can: measure the resistance on the removed chip between the 5V and gnd pin.

  20. #20
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    What I have right now is a dead short on mine. I had someone with a working board check theirs and they had 512 ohm.

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