dc POWER SUPPLY PROBLEM

Discussion in 'General Electronics Chat' started by alpha_tayyab, Jul 8, 2009.

  1. alpha_tayyab

    Thread Starter Member

    Dec 23, 2008
    11
    0
    Hi all of them
    i am facing a problem now a days
    problem is that i had bought a power supply from market, and it makes PROBLEM from the FIRST day i had bought this
    well PROBLEM is that, when i Swith ON the supply, display(DIGITAL VOLTMETER) works, but showing 0000 VALUES
    when i vary from KNOBS, then nothing is going to happen
    i open the POWER SUPPLY, and check fro the whole circuit that might be, if any thing burnt in it, then i must reploace, but every thing is OK from INSIDE
    i study this supply since last week but uinable to LOCATE the EXAXT FAULT
    if any one of you have any IDEA about this FAULT then must told me
    i also mention that, i CHECK VOLTAGE from DIGITAL MULTIMETER at different part of power supply, it SHOWS (20V DC) which mean that transformer is OK....
    so plz help me about this issue
    waiting
    TAYYAB
    ELECTRICAL ENGINEERING STUDENT
     
  2. someonesdad

    Senior Member

    Jul 7, 2009
    1,585
    141
    Very frustrating to buy a supply that doesn't work.

    It can be difficult to figure out what's wrong with a circuit without a schematic diagram. And lots of instruments these days have a lot of digital functionality on one chip; the schematic can be useless unless you also have the firmware source code.

    If there's nothing obviously wrong with the components, the best strategy would be to return it to the vendor under warranty, if that's possible.
     
  3. mik3

    Senior Member

    Feb 4, 2008
    4,846
    63
    Check if the the output voltage varies when you rotate the knobs.
     
  4. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    Like I said on the other website, it is Made In China.
    Don't buy no-name-brand cheap junk.
     
  5. Lanz

    Active Member

    Oct 30, 2008
    153
    0
    Well said.
     
  6. StayatHomeElectronics

    Well-Known Member

    Sep 25, 2008
    864
    40
    If it is anything like the cheap electronic junk toys that my kids get all the time, pull lightly at some of the wires, they may come right off. I can't tell you how many toys I have opened up after one day that quit working.
     
  7. R!f@@

    AAC Fanatic!

    Apr 2, 2009
    8,747
    759
    But I'll say it is not that bad, I see from one pic it uses a standard ADC IC as a voltmeter, can you get a detail pics of the boards that is inside, I can help you to fix it.

    Rifaa
     
  8. THE_RB

    AAC Fanatic!

    Feb 11, 2008
    5,435
    1,305
    Little fuse somewhere? A panel fuse or circuit breaker on the back of the unit? Or a fusible resistor on a PCB somewhere, looks like a resistor with a low value written on (often less than 1 ohm) and rough matte paint, not shiny. They blow open circuit.

    And check all the solder joints with a good magnifier. :)
     
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