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Fluctuating Voltages across PS!

Discussion in 'General Electronics Discussion' started by Onyxx, Apr 15, 2010.

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  1. Onyxx

    Onyxx

    4
    0
    Apr 15, 2010
    Hi guys, quick question; If you grab a volt meter and measure the DC voltage across the main cap (and other components as well) on the power supply from a DVD player and you see that the voltage goes back and forth from a few volts up to 300+ volts continuously (AC line here is 220), what do you suspect? Where do you look first?

    I have checked all the components but failed to find anything wrong. I am a beginner and this goes beyond my experience, I guess. If someone can point me in the right direction I will appreciate it!!!

    Thank you!
     
  2. Resqueline

    Resqueline

    2,848
    2
    Jul 31, 2009
    There's not much between the AC and the cap. A filter and a rectifier is just about it.
    Measuring the AC & the DC at the rectifier should indicate wether this is faulty.
    I guess the DVD doesn't work very well and that you have no reason to suspect the meter is flakey.
     
  3. Onyxx

    Onyxx

    4
    0
    Apr 15, 2010
    Thanks Resqueline,

    Yes, the dvd player does not even turn on and no, no reason to suspect the meter. The diodes on the rectifier measure OK but I will go ahead and change them anyway, mainly because I am not sure how to test them on a live circuit.


    Thanks again!


    Anyone else with ANY suggestions at all??? :)
     
  4. sheldonstv

    sheldonstv

    68
    0
    Jul 17, 2007
    can you either post a picture of the powersupply used or give the model nr of yr dvd player so i can have a look at the service manual????
     
  5. Onyxx

    Onyxx

    4
    0
    Apr 15, 2010
    Hello sheldonstv, thanks for your support. Here is the info you requested as it is printed on the PCB it self:

    MIZUDA REV:1.0A Power Supply Model: ST-11B. PBC
    P/N:20040907


    I decided that the rectifying diodes are Ok so I did not change them. However, I am suspicious of the chopper transformer. My question is; is it possible for a bad chopper t. to cause the symptoms described above?


    Thank you sheldonstv and anyone else who jumps in!
     
  6. Onyxx

    Onyxx

    4
    0
    Apr 15, 2010
    Sorry sheldondstv, I missunderstood your request. Here is the info for the DVD player it self:

    Brand: HYPSON
    Model (as far as I can tell): DVD-P306.

    Hope this helps and thanks again!!!
     
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