DM800HD rebooting

Discussion in 'DM800HD Hardware troubles and Repair support.' started by Abdulhady, Apr 22, 2020.

  1. Abdulhady

    Abdulhady New Member

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    Hello everyone.
    I have a DM800HD that is always rebooting in loop when loading image (it starts loading, then reboots, and the starts loading, a never ending process, in loop)
    Before this problem, the receiver was not receiving HD channels (DVB S2).
    Without the tuner A DM800hd is booting good.
    I have Tuner BSBE2-401A (DVB-S2) REV:K
    pls help me ,
     
  2. toysoft

    toysoft Well-Known Member Staff Member

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    4 Big Caps, to be replaced,

    TS
     
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  3. Abdulhady

    Abdulhady New Member

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    Thanks for the prompt reply
    Where is 4 BIg caps in the tuner or mb?
     
  4. toysoft

    toysoft Well-Known Member Staff Member

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    See Image here,

    caps.jpg


    TS
     
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  5. Abdulhady

    Abdulhady New Member

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    Many thanks for the fast reply !
    After changing 4 caps the device booting completely, but there is no signal.
    I have checked the 13/18 volts outside of the tuner. is ok
    Sorry for my weak language in English, I speak Arabic
     
  6. toysoft

    toysoft Well-Known Member Staff Member

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    It could then be now a problem in the tuner, Johnny could be able to give you better tips, or if you have another tuner board for DM800HDpvr, try to test it.

    TS
     
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  7. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    Since you first say that the box resets when it's set on HD channels, and now with new caps which I assume are correctly mounted and has not a extreme high voltage value, then I think it's a good idea to check the box with another power supply, one which is (of course) 12vDc and at leas has a Amps delivery of 3 amps.
    But be aware that the psu must have a normal polarization, thus the plus side is the center hole.
     
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  8. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    Assuning that the power supply is not the case,
    Check the main voltages, best is to do it by ohms values.
    See this picture which shows the ohm values of 3 different boxes PCB1 etc.
    Check if they are in a same range as shows on this picture.
    These ohm measurements were done between a ground spot and the measurement spot.
    [​IMG]
     
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  9. Abdulhady

    Abdulhady New Member

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    THANKS MR JB , Toysoft
    Can you see these values?
    my power supply is 12V 5A
     

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  10. Abdulhady

    Abdulhady New Member

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    After changing the image BlackHole to OpenPLi-2.1-beta-dm800-20140510 the tuner scan ch sd and hd Without HD frequencies DVB S2.
    I don't know what the problem is.
     
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  11. toysoft

    toysoft Well-Known Member Staff Member

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    Ok then this would mean that your Tuner has the HD problem, but it works with SD channels (am I correct ?).

    There is a trick with adding a Capacitor or fixing this perhaps replacing one (Johnny will know).

    TS
     
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  12. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    When looking at your ohm measurements I find both the 3.3v a bit low than normal, the rest seems to be fine.
    I'm not know if you have measured it with the tuner, but these values I had measured were done only with the motherboard, without front panel, tuner etc. connected.

    In any case, keep pin 3, the 3.3v from the U6 monitored while working with the box because I have the impression that there may be a issue with it.
     
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  13. Abdulhady

    Abdulhady New Member

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    Good evening
    All DVB -S frequencies are done with good , whereas the DVB-S2 frequencies are not working at all (SD-HD).
    Is the defect in the tuner or MB ?
    Attached are some pictures for illustration.
    Thank you so much
     

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  14. toysoft

    toysoft Well-Known Member Staff Member

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    I would bet on the DM800HD TUNER (Tuner board on the slot),... as the HD is a typical problem of the J/K Tuners.

    TS
     
  15. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    Of course, you could try it with another tuner when you have one, but to me it looks as if the 3.3v from the U6 is to low.
    As your measurements shows, it's 2.59v while it normally should be 3.3v with or without a tuner.
    It could mean that there's a higher power (amps) consumption on this 3.3v circuit and could be due cpu which uses this 3.3v, or other section which uses this voltages as also for example the 3.3v tuner cap C254 from this circuit.

    I think, best is to disable the U6/3.3v R118 zero ohm resistor from the circuit and check if the U6 side gives the normal voltages while it's not ballast.
    Suppose it's still to low, then you could check the two diodes D3 or D4 if they leaking, which does happen more often.
    But, when it's not caused due the U6 side because it has the 3.3v without connected to the circuit, then it becomes more difficult to find the reason why, anyways see this U6 picture for more info.

    One note, do not keep the box to long powered on while the 3.3v zero ohm resistor is disconnected from the 3.3v circuit because the cpu may become faster hot than it normally does due the missing 3.3v.
    Also better is to disconnect the front and tuner when you do that.

    Maybe a idea is to see/test if it's indeed caused due a to low voltages for the tuner is to disable the tuner 3.3v from the circuit by removing the L34 inductor to exclude it from the weak circuit.
    Use a Dc to Dc step down module/converter to feed the 3.3v to the tuner and see if it helps.
     
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