DM8000 blue light only when power on

Discussion in 'Hardware troubles and Repair support.' started by mwd123, Aug 12, 2017.

  1. 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:
    I've did some tests to see if I'm be able to create your fault on the motherboard but without success.
    I have measured some vdc voltages on the board, it's random but maybe you find some faulty voltage on it which may give a direction were to look further.

    When you measure the sensitive crystal side, the box may crashes, the display goes off, two blue leds flashes, or goes on or off.
    When measure this spot you need afterwards to switch off the box, and turn it on when it's unloaded.


    See picture, click on it for a full view.
    dm8000hd-vdc-Snap.jpg
     
  2. allllex

    allllex New Member

    Messages:
    16
    Likes Received:
    0
    Trophy Points:
    1
    Gender:
    Male
    Here are my measurements of stresses.
    Different values are indicated in yellow.
    During measurements, the display on the front panel remained dark all the time. Did not react to the measurements.
    When measuring the voltage in the lower right corner with an explanation, the blue button also glowed.
    When it is reset, the button in one test is turned off and does not turn on.
    In another experiment, the button constantly blinked and did not react.
    In the third experiment, the button did not turn off and constantly burned.
    It was necessary to switch off and turn on the box with the rear switch on the box.
    The display did not react during the measurement and was always black.

    The TV and satellite dish are not connected to the box.
     

    Attached Files:

    Last edited: Oct 22, 2017
  3. 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, tomorrow I could check these differences.
    There are at least some strange things going on as the crystal voltage 0,36v which is the crystal from the U400 - NTSC-PAL-SECAM decode chip.
    Somehow it seems to be inactive, but it may have to do with the booting up state.

    As for the U1105/LD1117A input/output voltage differences, is also a bit strange, it looks as if your input voltage is to high while I thought its fixed for an output to 2.6v.
    But maybe it's not fixed/adjusted.

    As for the sensitive crystal J800 which is for the U807 - AVR microcontroller - ATMEGA8535L.
    This seems to work, and lucky it does otherwise it can not be replaced for a new one because these chips are programmed for the dm8000hd.

    In any case, as far as I see it for now it looks as if the cpu has stopped working, but it's still to early to say if it's really the case.
    It still not have to be the cpu itself, it can be caused due a problem to the cpu as the bios rom or other cause.

    You have now checked the main voltages, next plan will probably be to measure some ic's or chips.
     
  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:
    Sorry, not had the time to do some research on your problem, maybe Wednesday, otherwise not earlier then the upcoming weekend.
     
  5. 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:
    I've a question about your box..
    Are you be able to switch the box On/Off with the front push button?
     
  6. allllex

    allllex New Member

    Messages:
    16
    Likes Received:
    0
    Trophy Points:
    1
    Gender:
    Male
    "Are you be able to switch the box On/Off with the front push button?"
    Yes, I can turn on / off the box with the front push button.
    I can turn on the box from the remote control, if before that the box was turned off with the front button.
    I can not turn off the box by the remote control.
     
  7. 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 is the box basically working, but can't most likely read the data from the nand flash chip.
    Could be that the data is corrupt, or the nand chip failed or contact issues between the nand flash chip and the cpu.

    Two options, I think.
    One, but risky to check... turn the box off with the front push button, heat up with hot air the right side of the cpu.
    than the display may become to life.
    However it's risky and it probably not solve the problem, if it's react than the cpu must probably be re-flowed.

    When it does noting then it could be the nand flash chip self, which needs to be replaced for a new one.
    And based on you story, it could be the nand flash chip.
     
  8. allllex

    allllex New Member

    Messages:
    16
    Likes Received:
    0
    Trophy Points:
    1
    Gender:
    Male
    If I replace with the new nand flash chip, will I have a COM port, so that the FerrariFiller program will load the bootloader into it?
    You wrote:
    At this moment, FerrariFiller does not see the box.
    Does the nand flash chip include a COM port?
    And can non-working nand flash disable the COM port?

    Heating the CPU with a hair dryer did not solve the problem.
     
    Last edited: Oct 29, 2017
  9. 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:
    It depends,
    If the nand flash chip data is corrupt then you could see some serial output with a serial terminal program.
    The display should give some information etc.

    Only when the nand flash chip has a defect, and so some low ohm value on one of the four I/O data ports then it may give the issue you describe.
    You are normally be able to measure it, just measure these I/O pins to see if they are all four has a Mohm value and are all in the same range.
    When not, then it could be a defective nand flash chip, or a issue from/to the cpu.

    As for which pins are used/connected, see this picture..
    flashchip-connected-pins.jpg

    In any case, yesterday I had taken a old dm8000hd board which has the same symptoms as you have.
    I had it for years to use for the parts, but since you have this issue I had taken it to see if I could find the issue.
    Yes, it has precisely the same symptoms as you have, same measurements on the display as if it's into standby mode etc..
    However, when I had set it into standby mode by pressing the front push button, and use my hot-air station to warming up some sectors I noticed that when I did it on the right side of the cpu, the board turned on, and the display gave the normal message, but when it's cooled down, it failed again.
    When measuring the I/O data pins from the nand flash chip I saw that they were not all into the same ohms range.
    After I did a cpu re-flow process with my bga station it were fixed, the board still works.

    In any case, this board had a cpu issue, bad contact with the solder balls beneath.
    I'm not claiming that it may also be the same case as you have, but when the cpu has some bad contact with the motherboard it could give these issue.
     
    Last edited: Oct 29, 2017
  10. allllex

    allllex New Member

    Messages:
    16
    Likes Received:
    0
    Trophy Points:
    1
    Gender:
    Male
    The voltage at the terminals Vcc = 3.39 volts.
    The resistance of I / O0 - I / O7 is almost the same and is 4.72 - 4.74 Kom.
    When the box is turned on, the voltage across all these I / O pins is 3.38 volts.
    When the box is turned off from the button on the front panel reduces the voltage at all I / O pins to 0.33 volts, and Vcc = 0.33 volts.
    Hyperterminal does not provide any information.
     
  11. 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 I will check your measurements tomorrow, in any case it seems that you have no issues between the chip and the cpu and so your case seems to be different than the case I had yesterday.
     
  12. allllex

    allllex New Member

    Messages:
    16
    Likes Received:
    0
    Trophy Points:
    1
    Gender:
    Male
    Additional Information.
    At me this box often in 7-8 hours of operation hung, and after that did not boot. It was necessary to wait about 2 hours, so that it began to load again.
    But Hyperterminal always showed a boot log and the display always showed the boot image on the display.
     
  13. 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:
    Yeah okay, that can also be caused due the cpu.
    But let see if it's not due it, if that is the reason why the box not boot up.
    It does not always happens due the cpu, in some cases it's due other causes.

    Nevertheless, it is an old box whose expected lifespan has expired and the production has stopped years ago somewhere in 2012.
    Spend money to it is a risky choice so thinking of re-balling the cpu seems to me not the wisest solution, more re-flowing but has some risks, it may end up with a un-repairable motherboard, especially when it's a clone board because a original motherboard is from better quality and can handle the job better from my experience.
     
  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:
    New attempt, check these..
    dm8000hd-u1106-vdc.jpg
     
  15. allllex

    allllex New Member

    Messages:
    16
    Likes Received:
    0
    Trophy Points:
    1
    Gender:
    Male
    There are differences
     

    Attached Files:

  16. 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:
    check the ohm value between the ground and the L1108 coil, it should be something as 372.49 ohm
     
  17. allllex

    allllex New Member

    Messages:
    16
    Likes Received:
    0
    Trophy Points:
    1
    Gender:
    Male
    12,82 Kom
    Replaced the battery in a multimeter. 13,7 kom.
     
    Last edited: Oct 31, 2017
  18. 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 there is something wrong.
    To determines if the problem comes from this circuit, (most likely the 8p mosfet ic,) or the circuit which use this voltage it better to separate the L1108 coil from the circuit and measuring by ohms both sides.
    The coil does not have to be removed, one side is enough.
    Just lift it up gently when the solder is liquid.

    Tomorrow I'm be able to do the same to know the good ohm values.
     
  19. allllex

    allllex New Member

    Messages:
    16
    Likes Received:
    0
    Trophy Points:
    1
    Gender:
    Male
    measured the resistance
    R l1108 = 0 om
    U from above = 0 volt without L1108 (1,8V), R = 13 kom
    U bottom = 3.3 volt without L1108 (1,52v), R = >2 mom
     
    Last edited: Oct 31, 2017
  20. 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:
    U from above = 0 volt without L1108 (1,8V), R = 13 kom
    U bottom = 7.2 volt without L1108 (1,52v), R = >29.47 kom

    So, based on this it seems to be the Dc to Dc circuit itself, and not because of a heavy load from a other source.
    It's a bit of a guess but I think you need to replace the fds 6982s 8pins ic to get the 1.8v back.
    See the fds 6982s datasheet for more about this.

    In any case, as far as I can measure the output of it, it's the voltage for the memory and probably also for the cpu, and so a important voltage which needs to have the correct voltage to operate properly.