Help to identify the components of Power Supply.

Discussion in 'General Electronics Chat' started by RdAdr, Aug 19, 2016.

  1. RdAdr

    Thread Starter Member

    May 19, 2013
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    I have a power supply and I don't know what components are the ones I highlighted in the attached image.

    Can someone help?

    3-n1.jpg

    3-n2.jpg
     
  2. dl324

    Distinguished Member

    Mar 30, 2015
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    The three terminal device is probably a transistor or diode. The other looks like a capacitor.
     
  3. RdAdr

    Thread Starter Member

    May 19, 2013
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    I thought it is a transistor too. The power supply is bad and I noticed that one of those transistors is shorted on any of its three terminals.
    Do you know what kind of transistor is that?
     
  4. bertus

    Administrator

    Apr 5, 2008
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  5. RdAdr

    Thread Starter Member

    May 19, 2013
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    There is no code. It is all black.
     
  6. cmartinez

    AAC Fanatic!

    Jan 17, 2007
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    I agree with the thing that looks like a capacitor. But the three pin device could be anything from a diode (yes a I've seen them in that sort of package), to a linear regulator, transistor or mosfet. But most likely it is a transistor, as has already been noted by other members. Either look for the numbers with a magnifying glass, or see if there's another component like it on the board, and try to test it.
     
  7. RdAdr

    Thread Starter Member

    May 19, 2013
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    Also what about the big yellow thing in the top right corner?

    I suppose it is an inductor, but it has so many pins attached to it on the other side
     
  8. ian field

    Distinguished Member

    Oct 27, 2012
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    The 2 terminal beige bit is almost certainly a capacitor - I can't ever remember seeing one with component markings.

    On statistical probability; the 3 terminal black bit could well be a transistor - but there's an awful lot of 3 terminal devices available in that SMD package style.

    On a PSU; a 3 terminal device close to an SOIC8 could just as easily be a TL431.

    There should be an alphanumeric code on it - google for SMD code books, You'll probably find several different devices share the same code - exact identification of the package style usually pins it down to a single device type.
     
  9. AnalogKid

    Distinguished Member

    Aug 1, 2013
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    That probably is the system power transformer. Immediately below it is the primary side switching device. The long black rectangle below that is the input bridge rectifier. The coils to the left of the bridge are the powerline noise filter, along with the small blue parts that are Y capacitors and the 0.47 uF X capacitor in the middle. The large inductor above that probably is an output choke. All guesswork...

    ak
     
  10. recklessrog

    Member

    May 23, 2013
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    What is the power supply from?
     
  11. ElectronicMotor

    Member

    May 1, 2016
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    Yea Capacitor, Transistor (BJT, Enhancement MOSFET, Depletion MOSFET, FET) ?
     
  12. ian field

    Distinguished Member

    Oct 27, 2012
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    The toroid inductor could be part of a PFC front end - but it doesn't look the right place relative to the layout of the mains in components.

    PC1 is a regulation feedback isolation optocoupler - the 3 terminal on the other side could be a TL431, but not 100% guaranteed.

    The missing resistor is either a source current sense resistor, or a drain/primary snubber - slight heat discolouration on the board suggests the latter. Source resistors usually blow open circuit with little or no getting hot. Source resistors are usually less than 1R - snubbers tend to be a few k or tens of k.
     
  13. ElectronicMotor

    Member

    May 1, 2016
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    I have gone up and down that photo five times and have not seen a power transformer

    Stay on subject
     
  14. ian field

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    Its on the image in post 7.
     
  15. ElectronicMotor

    Member

    May 1, 2016
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    Post 7 missed it sorry o_O
     
  16. ElectronicMotor

    Member

    May 1, 2016
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    After a lifetime of fixing this stuff, from top to bottom, left to right

    Primary switching MOSFET / IC

    Switch-mode power transformer

    Primary filter cap 400V 100u

    Mains filtering coil

    Current/Voltage regulation feedback opto-coupler

    Output voltage regulator

    The blue and red caps are special. They have to pass strict Government end of life criteria

    More filtering, more filtering, more filtering

    And, ala de crem, the mains full wave rectifier
     
    Last edited: Aug 19, 2016
  17. ian field

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    Oct 27, 2012
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    They're laser-cut and sometimes very faint.

    I start by washing off any residual flux with solvent, usually wiping with a dry finger removes any smear that might obscure the number.

    After that you can try using a jewellers loupe and a LED flashlight to catch the light at the right angle to reveal the numbers.

    Sometimes wiping over with a moistened finger brings the numbers up.

    If the tracks trace over to the optocoupler - its probably a TL431.
     
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  18. bwilliams60

    Active Member

    Nov 18, 2012
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    I find that a good camera will pick up a faint number and when you take it and then zoom in on it, it becomes very clear. May have to take it with different lighting sources and angles.
     
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  19. cmartinez

    AAC Fanatic!

    Jan 17, 2007
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    Good one... also, some phone cameras are able to enhance an image in the infrared, which could reveal additional detail
     
  20. SLK001

    Well-Known Member

    Nov 29, 2011
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    Look again. I can see something, even with the crappy photos.
     
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