DM8000 PSU not working

Discussion in 'Hardware troubles and Repair support.' started by Greystoke, Apr 3, 2017.

  1. Greystoke

    Greystoke New Member

    Messages:
    17
    Likes Received:
    2
    Trophy Points:
    3
    At the moment I have PC100, PC200, PC300 and T200 off the board.

    With L200 removed I am getting 24.9v on T100 side.
    And 0v on cn300 side.

    Just measured it again after typing this and getting 28.9v on T100 side.

    It's like after it warmed up the voltage increased.
     
    Last edited: Apr 5, 2017
  2. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

    Messages:
    2,269
    Likes Received:
    1,026
    Trophy Points:
    113
    Gender:
    Male
    Location:
    Netherlands
    Home Page:
    Hmm, no clue what to think of and I have only working ones.
    Therefore I could only tested this with the working psu's.
    Tested with two, and both were 48.7 vdc from the T100 transformer without the L200 jumper.

    So in your case without the optocouplers may be a different story, or the transformer has some issues on the inputs, hot side.
    In any case is the IC101 involved with it, and I still have some doubts about your ohm measurement results from the IC101.
    I do not know if the T100 still operates without the IC101, but to me it seems worth to try.
    Suppose it is removed, and you have the 48v from the T100, then it's most likely that the IC101 is defective.
    Nevertheless I did not have test this, and so I can not say what the results may be or if it's give some damage to other parts.
    You may wait unit friday/saterday then I'm be able to do some more tests.

    However, again the warning.. keep in mind that the caps may be loaded so be careful with that, best is to unload the big caps with a lamp.
     
  3. Greystoke

    Greystoke New Member

    Messages:
    17
    Likes Received:
    2
    Trophy Points:
    3
    I have replace IC101, IC100, IC200, PC100, PC200, PC300 off another board and still the same.

    Could it be the T100, the inputs are all 326v.
    Do you have a part number or specs for this transformer.
    I couldn't swap the T100 from the other board I have as it has only 4 pins on the output, mine has 5 pins
     
  4. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

    Messages:
    2,269
    Likes Received:
    1,026
    Trophy Points:
    113
    Gender:
    Male
    Location:
    Netherlands
    Home Page:
    The T100 use on the hot side four pins, one center pin of the second coil is not connected to the mainboard.
    However, there is always the risk that the coil values not been the same.
    And, I have never had a psu in repair with a transformer failure, to me it seems very rare if this is the case.
    Since you have exclude most of the parts by replacing them, than it seems to me more a diode issue which lowers the voltages.
    I can not thing of which it may be, but thinking of the hot zone and the T100 hot side, then it could be maybe in the D106 circuit.

    But again, you can see this on this dm7020 psu schematic which is for the most parts the same.
    Just see the 9.5v circuit on it.
     
  5. Greystoke

    Greystoke New Member

    Messages:
    17
    Likes Received:
    2
    Trophy Points:
    3
    Just replaced D106. Still getting the 8v
     
  6. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

    Messages:
    2,269
    Likes Received:
    1,026
    Trophy Points:
    113
    Gender:
    Male
    Location:
    Netherlands
    Home Page:
    Sorry but since you have already so much replaced on this 14v circuit I have at this moment no other ideas were to look.
    Maybe it is a resistor whit a wrong value, maybe it's better to measure some circuits by Ohms instead of voltages.
    But I have no Ohm values notes from it, but I can do this in the weekend.
     
  7. Greystoke

    Greystoke New Member

    Messages:
    17
    Likes Received:
    2
    Trophy Points:
    3
    I replaced zd101, c104 and d104 and it is now working.

    After putting the originals back in it is still work.
    Going to replace these with new ones as one has to be on the way out.

    Would you have the specs for zd101 and d104 so I can order these parts.
    Is this the correct part for zd101:
    http://ie.farnell.com/nxp/bzx79-c15/diode-zener-15v-500mw/dp/1097217
     
    Johnny B. likes this.
  8. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

    Messages:
    2,269
    Likes Received:
    1,026
    Trophy Points:
    113
    Gender:
    Male
    Location:
    Netherlands
    Home Page:
    Okay, so it was in the D104 circuit, good job, congrats.
    As for the c104 and taken the dm7020 schematic, then it give there the 47uF 50v and the D104 seems to be an T3D 47 diode.
    Only the Zener diode zd101 I don't know, but maybe I'm be able to see this on one of my power supply's.
     
  9. Greystoke

    Greystoke New Member

    Messages:
    17
    Likes Received:
    2
    Trophy Points:
    3
    The zd101 has c15 5t on the side of it
     
  10. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

    Messages:
    2,269
    Likes Received:
    1,026
    Trophy Points:
    113
    Gender:
    Male
    Location:
    Netherlands
    Home Page:
    In that case, searching google to diode c15 5t it seems to be the BZX55/C15
     
  11. Greystoke

    Greystoke New Member

    Messages:
    17
    Likes Received:
    2
    Trophy Points:
    3
    Thank you for all your help get this working again.
     
    Johnny B. likes this.
  12. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

    Messages:
    2,269
    Likes Received:
    1,026
    Trophy Points:
    113
    Gender:
    Male
    Location:
    Netherlands
    Home Page:
    No problem, it was a pleasure to help you out with it.
    And it may be educational for others who experience this issue.
     
  13. nipon0007

    nipon0007 New Member

    Messages:
    18
    Likes Received:
    3
    Trophy Points:
    3
    Gender:
    Male
    This problem your box show blue light only when turn on?
     
  14. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

    Messages:
    2,269
    Likes Received:
    1,026
    Trophy Points:
    113
    Gender:
    Male
    Location:
    Netherlands
    Home Page:
    @nipon0007

    This case was a issue with the main voltage 14v, and so I think not that is gave the front led light.
     
  15. toysoft

    toysoft Well-Known Member Staff Member

    Messages:
    376
    Likes Received:
    459
    Trophy Points:
    63
    Gender:
    Male
    Location:
    Switzerland
    Home Page:
    Just a little thing, did you tried to replace the cap I crossed in red ?

    TS[​IMG]
     
    Johnny B. likes this.
  16. toysoft

    toysoft Well-Known Member Staff Member

    Messages:
    376
    Likes Received:
    459
    Trophy Points:
    63
    Gender:
    Male
    Location:
    Switzerland
    Home Page:
    FYI

    Blue button flashing or stable ? How to...

    1) Flashing blue in the powerbutton
    Flashing blue light = Tuner problem or Ground problem (so try to rebuild the box checking the grounds).

    2) Stable blue in the powerbutton - How to
    PSU needs to be repaired / replaced.
     
    Johnny B. likes this.