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help fixing satellite receiver power supply circuit

Discussion in 'Troubleshooting and Repair' started by pharaon, Mar 26, 2020.

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  1. pharaon

    pharaon

    280
    3
    Oct 28, 2014
    the board output is dead
    can some one help me track the voltage path through the board, so i would check what component is really not working , i'm suspicious in "power IC" or "photo-coupler"

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  2. Harald Kapp

    Harald Kapp Moderator Moderator

    9,668
    2,019
    Nov 17, 2011
    Start by checking the input:
    upload_2020-3-26_13-16-13.png
    Is there a rectified input voltag eacross the electrolytic capacitor (marked red)?
    Is the fuse conducting or open?
     
  3. pharaon

    pharaon

    280
    3
    Oct 28, 2014
    the fuse is alright
    and there's voltage on the capacitor
     
  4. 73's de Edd

    73's de Edd

    2,805
    1,176
    Aug 21, 2015
    Sir pharaon . . . . .

    Is your DC voltage being somewhat in the order of + 320---340 across the BIG BLUE main filter capacitor ?
    If so, then that voltage passes to the corner terminal of the power transformer primary and comes out of the winding as the third down . . .of the four terminals on that side of the transformer and that terminal then feeds into the nearest corner of the 8 pin " all in one " power IC for the system.
    The IC's power return to ground is thru the 0.51 ohm resistor on the other side of the IC to the negative side of the BLUE cap.

    There is being the single power FET switching transistor built within that IC and the involved internal control electronics.
    I am expecting that the FET shorted and if severely overloaded might have shown plastic case damage or bulging.
    Also the 0.51 may now be open circuit.
    Pass back the part numbering on the 8 pin IC . . . . . and it may be a Viper series unit. . . . . of one manufacturers products.

    Once the IC gets its initial "kick starting" it then uses its other separate primary winding to feed thru the 11?ohm resistor and get rectified by D5 to feed C7 / 8 to develop the normal run voltage supply for the IC with a littlle regulation assist from the ZD1 and 2 zener diodes.
    ANY of those could ALSO be your BASIC problem instead of the IC.

    If the R5 0.51resistor is not blown, you could get some what of an initial analysis of the units basic switch mode circuit operation by placing a mini pocket AM transistor radio right atop the power transformer .
    The radio is to be tuned off of any station and its volume is at max.
    Then plug in your power supply and see if the radio sounds off like a TEXAS size mosquito. If not . . . .no pulse switching activity is being generated.
    If uncertain of the above procedure, initially bring the radio up to the face of an operating TV or monitor and then play around with the positioning of the radio to find the most sensitive direction of signal pick up. Apply that then learned positioning importance, to the positional alignment to the power transformer.

    PLUS, by that initial familiarization , you will then DEFINITELY know what you are expecting to be heard.

    Thaaaasssssssit . . . . . fer now . . . .


    73's de Edd . . . . .

    Now, I just have to ask you . . . . is it all right for a vegetarian to eat animal crackers ?

    .
     
  5. pharaon

    pharaon

    280
    3
    Oct 28, 2014
    323.5 DC

    On the buzz mode it's open circuit, but on ohm scale it give me 0.59 ohm

    _20200326_222656.JPG
     
  6. Bluejets

    Bluejets

    3,787
    783
    Oct 5, 2014

    Attached Files:

  7. pharaon

    pharaon

    280
    3
    Oct 28, 2014
    are you sure it should be turned off?
     
  8. 73's de Edd

    73's de Edd

    2,805
    1,176
    Aug 21, 2015
    It should be turned " off " . . . . . meaning not tuned into any station, so that the radio can then only
    pick up the switch mode signal harmonics that would be emitted, IF, the unit is working.
     
  9. pharaon

    pharaon

    280
    3
    Oct 28, 2014
    Couldn't hear any difference really since AM frequency is loud noise anyway but not the same noise i hear when i close the radio to the TV, is there any other way to test it
     
    Last edited: Mar 27, 2020
  10. debe

    debe

    239
    64
    Oct 15, 2011
    Check the marked 470K resistor as it looks like its the kick start resistor. 2.jpg
     
  11. pharaon

    pharaon

    280
    3
    Oct 28, 2014
    the resistor is alright
     
  12. pharaon

    pharaon

    280
    3
    Oct 28, 2014
    so anything else to check or is it the power IC
     
  13. debe

    debe

    239
    64
    Oct 15, 2011
    You could try replacing the 2 small elctrolytics near the IC, one of them goes to Vcc pin7. If this doesnt work then probably replace the IC.
     
  14. pharaon

    pharaon

    280
    3
    Oct 28, 2014
    which one exactly?
    do you mean R5 ,R6? or the two diodes 06,05
     
  15. debe

    debe

    239
    64
    Oct 15, 2011
    Marked with yellow dot. 2.jpg
     
  16. pharaon

    pharaon

    280
    3
    Oct 28, 2014
    how can those be an issue
     
  17. debe

    debe

    239
    64
    Oct 15, 2011
    They are part of the Ic power supply on pin 7. Look up data on ICE2B265 it describes how the system actualy works.
     
  18. pharaon

    pharaon

    280
    3
    Oct 28, 2014
    but will they cause the Ic to not work at all?
    anyway i'll change them and see
     
  19. pharaon

    pharaon

    280
    3
    Oct 28, 2014
    any addition measurements i should do before i change the power IC? i mean to make sure there's no other failure components that would harm the new power IC
     
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