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Faulty Power Supply

Discussion in 'Troubleshooting and Repair' started by partyanimallighting, Feb 28, 2014.

  1. partyanimallighting

    partyanimallighting

    278
    2
    Oct 22, 2012
    Hello anyone,

    I've got a faulty power supply from and outdoor LED unit that I'd like to try to repair. I replaced this power supply with one from a working unit to test and this one definitely has a problem. The unit is an outdoor LED PAR with 48 LED's, 12 red, green, blue and amber and the working power supply that was tested outputs 48VDC and 12VDC from the terminals. The defective power supply outputs 48VDC from both terminals so I believe it's overdriving the main circuit board with the LED drivers. I'll be grateful for any assistance. I uploaded a picture of the power supply and a drawing showing the part numbers for the main rectifiers etc. I dabble a bit in repairs but as far as identifying parts by name, well..........

    Thanks,

    partyanimal

    http://www.4shared.com/account/home.jsp#dir=Z2q4Rk-B
     
  2. Harald Kapp

    Harald Kapp Moderator Moderator

    9,304
    1,888
    Nov 17, 2011
    The link requires a password.
    You can upload images directly using the "go advanced" button at the end of this page and the paperclip symbol to add an attachment.
     
  3. partyanimallighting

    partyanimallighting

    278
    2
    Oct 22, 2012
    Photos

    Here's an image and a drawing
     

    Attached Files:

  4. shrtrnd

    shrtrnd

    3,670
    453
    Jan 15, 2010
    You've obviously lost voltage regulation.
    Start with the easy stuff first.
    Closely examine the bad power supply.
    Do you see any burned parts?
     
  5. partyanimallighting

    partyanimallighting

    278
    2
    Oct 22, 2012
    Hi shrtrnd, I'm not seeing any signs of burnt out parts or scorching on the board. I did check the rectifier and I'm getting 120V AC coming in but the DC voltage coming out fluctuates between 135V to 150V DC. I doubt that's right.
     
  6. kpatz

    kpatz

    247
    52
    Feb 24, 2014
    A schematic would be really helpful.

    The output from the rectifier is pulsed DC, which typically will read higher than the incoming AC voltage. However, it should be filtered by a capacitor to make it smoother, so if it's fluctuating, it could indicate one of the big filter capacitors is bad.

    The best thing to do, since you have an identical working power supply, is to take readings on both and see where they differ.
     
  7. partyanimallighting

    partyanimallighting

    278
    2
    Oct 22, 2012
    Hi kpatz, my knowlege is really basic, a little troubleshooting here and there. Where do I start? A schematic would also be near impossible to get my hands on. Chinese product..........
     
  8. Harald Kapp

    Harald Kapp Moderator Moderator

    9,304
    1,888
    Nov 17, 2011
    Start by comparing voltages at different points of both the working and the defect power supply, working from the input towards the output. Once you find a big discrepancy, you're near the spot of the fault.
     
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