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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


    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


    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


    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


    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


    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

    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


    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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