PLEASE HELP ME TO REPAIR DM800HD

Discussion in 'DM800HD Hardware troubles and Repair support.' started by Ruwansagara, Mar 12, 2017.

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  1. Ruwansagara

    Ruwansagara New Member

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    hi i am here again after long time and want to repare my dm800hd anyhow .
     
    Ruwansagara, Oct 3, 2019
    #21
  2. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    Do you still talking about your dm800hd which you accidentally had connect a 12v ac supply to it, or is it now another one with other symptoms.
     
    Johnny B., Oct 3, 2019
    #22
  3. Ruwansagara

    Ruwansagara New Member

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    Yes sir i am tallking about the old one. Unable to repare it yet. I had some serious helth problems due to a hart problem and had a bypass sergery. So i unable to attend this kind of staff during last few months. Now i had time to do this. So plese help me.
     
    Ruwansagara, Oct 4, 2019
    #23
  4. Ruwansagara

    Ruwansagara New Member

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    Sir do you think is there any improvement if i change all electrolytic capasitors with new ones with same capacity and voltages
     
    Ruwansagara, Oct 4, 2019
    #24
  5. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    Sorry to hear that, but at least you survived the surgery with hopefully many more years to go.

    As for the caps replacement, and whether it may be useful, it is the four caps C112 / C113 / C114 / C115
    More about is, see this drawing.
     
    Johnny B., Oct 4, 2019
    #25
  6. Ruwansagara

    Ruwansagara New Member

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    When i was ill I gave my dm 800 to a repare prson who repare electronic items. Today I connect the power supply to the dm. But dm is completly dead. I re cheked it with a new power supply. But it is same. Two leds on lan port also not glowing. Tomarow i will chek circuit again with my mulimter and let you know the result. Now i think about buy a new mother board. Can you please gide me to buy a right one
     
    Ruwansagara, Oct 5, 2019
    #26
  7. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    When you have an network cable connected, and you see no activity with the network leds, and further also no other activity as the front led.
    Then it must be a issue with the power supply, or one of the input inductors are interrupted.
    More about this, see the dm800hd 12v (input) issues. topic.

    When searching on Ebay for a new dm800hd motherboard I found one seller ans ask more than 168 euro's for it, it seems to me a bad choice while a newer box as the dm520 could be found for around the 100 euro.
     
    Johnny B., Oct 5, 2019
    #27
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  8. toysoft

    toysoft Well-Known Member Staff Member

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    Generally the four caps C112 / C113 / C114 / C115 solution works great,

    TS
     
    toysoft, Oct 5, 2019
    #28
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  9. Ruwansagara

    Ruwansagara New Member

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    This is what repare person had done to my dm800 board
    1570346964074-699639040.jpg 1570347332019-1194118976.jpg
     
    Ruwansagara, Oct 6, 2019
    #29
  10. Ruwansagara

    Ruwansagara New Member

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    1570348073080-728727204.jpg
     
    Ruwansagara, Oct 6, 2019
    #30
  11. Ruwansagara

    Ruwansagara New Member

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    Please look around L36 and 37
     
    Ruwansagara, Oct 6, 2019
    #31
  12. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    The L111 and L36 are plus side coils, the L222 and L37 are minus (ground) coils.
    Just check them, measure if they let through and none is interrupted.
    They are inductors, like coils, but just imagine that they are fuses and therefore measure them as if they were fuses.
    When one is interrupted, for example and because you seems to have one coil on the minus side, then the whole box is death.

    See this picture how it looks,
    [​IMG]

    However, these inductors are become only defective when there was/is a heavy power consumption or when there is a short circuit on the motherboard side.
    Check the 12v ohm value circuit between the plus side, and the ground after the inductors.
    It should be around the 990 ohms, much lower than that may indicate a short circuit from one of the parts of the 12v circuit.
    See this, for the ohms values,
    [​IMG]
     
    Johnny B., Oct 6, 2019
    #32
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  13. Ruwansagara

    Ruwansagara New Member

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    what happen if the 222 is missing in pcb
     
    Ruwansagara, Oct 7, 2019
    #33
  14. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    When one is missing, the other must tolerate all Amps consumption and this can become the weakest circuit.

    Just check if you have the 12v +/- between the pin 6 and 7 or 8.
    When not, then you may have an interrupted inductor, most logic could be the L37.
    [​IMG]

    Fore more information about the 12v circuits, see the 12v (input) issues topic.
     
    Johnny B., Oct 8, 2019
    #34
  15. Ruwansagara

    Ruwansagara New Member

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    today i replaced all 4 capacitors c112, c113, c114, c115 and mesured p5 voltages with a new multimeter redings as folow
    pin 01- 1.21v
    pin 02- 2.58v
    pin 03- 3.27v
    pin 04- 3.27v
    pin 05- 5v
    pin 06- 11.65v
    pin 07- 0v
    pin 08- 0v
    then i mesured front panel conecto pin voltages without display and sim removed. folowing picture shows readings. please give me your valuble advices display.jpg
     
    Last edited: Oct 9, 2019
    Ruwansagara, Oct 9, 2019
    #35
  16. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    And even with all these voltage present is the dm still completely dead without any signs of life?

    I think, check these (J1) 1 to 6 pins by ohms, it should be in the ohm ranges as show in this picture, the values measurement from 3 pcb's, PCB1 etc.
    [​IMG]

    Measure it between a ground spot and the pins.
    Disconnect the power-supply when you do the ohm measurements.
     
    Johnny B., Oct 9, 2019
    #36
  17. Ruwansagara

    Ruwansagara New Member

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    Two lan leds glow. Procesor fan is working. No display.
     
    Ruwansagara, Oct 10, 2019
    #37
  18. Ruwansagara

    Ruwansagara New Member

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    These are the ohms readings in p5 refference pin is pin no 8

    Pin 01- 104
    Pin 02- 422
    Pin 03- 195
    Pin 04- 1130
    Pin 05- 365
    Pin 06- 1007
    Pin 07- 0
     
    Last edited: Oct 10, 2019
    Ruwansagara, Oct 10, 2019
    #38
  19. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    Pin 01- 104 = okay
    Pin 02- 422 = wrong (U7)
    Pin 03- 195 = wrong (U6)
    Pin 04- 1130 = okay
    Pin 05- 365 = wrong (U6)
    Pin 06- 1007 = a bit high, but okay
    Pin 07- 0 = Gnd thus okay

    low ohm value, the voltages 2.6V, 3.3V, 5V
    I'm a bit confused because of the involvement of the 2.6V U7 which has no direct connection to the other two circuits.
    Before I go further with thinking about this, I need to know,

    Do you have measured these ohm values with, or as it should be, without the tuner connected.

    Because these ohm values are all measured with no tuner etc. only the motherboard without any other things connected to or on it.
     
    Johnny B., Oct 10, 2019
    #39
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  20. Ruwansagara

    Ruwansagara New Member

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    Yes sir
    I mesured all these values without power conected, without tuner, front panel, and sim. only the mother board. Mesured with a digital mutimeter in 2k range.
     
    Ruwansagara, Oct 11, 2019
    #40
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