Repair DM800

Discussion in 'DM800HD Hardware troubles and Repair support.' started by VetallRX, Aug 25, 2018.

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  1. VetallRX

    VetallRX New Member

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    Hello! I have a desire to repair the DM800 rev:J
    When I turn on the receiver: the LAN LEDs are lit, the red LED illuminates for a few seconds and then starts flashing. If I press the power button, the red LED either goes out or starts to shine continuously.
    Voltages P5 1.24V; 2.60V; 3.34V; 3,30 V; 5,05V; 12.23V.
    At pin 1 SIM cards (with and without it) 5V goes to 0V. I do not know whether the SIM card is 100% workable.
    At Y1 1.60V, 1.60V; to Y2 1.01V, 0.8V; Y3 0V, 0V - I think not everything is good here.
    At the interface of the display, too, some voltage is not normal.
    Could this indicate a malfunction of the CPU, does the problem lie in something else?
    I would appreciate any tips.
    P.S. Sorry for my English, I use the Google translator to help
     
    VetallRX, Aug 25, 2018
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  2. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    It could be due the Cpu, but see first if you get some terminal output from the box with a program as Putty or Hyperterminal in serial mode.
    Use the serial rs232 port for it, use a null modem cable with the pins 2 to 3 / 3 to 2 and 5 (ground) to 5
     
    Johnny B., Aug 26, 2018
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  3. VetallRX

    VetallRX New Member

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    Thank you for answering. The terminal program displays some rubbish. It seems that the problem is in the processor. I will try to measure the generation on quartz, and using the oscilloscope to see if there is any movement on flash chips and others.
     
    VetallRX, Aug 26, 2018
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  4. toysoft

    toysoft Well-Known Member Staff Member

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    If I remember well you need to set the RS232 port to 115200 bps, or 9600 bps or 19200 bps, and you will have text, this will qualify that the CPU / box is working.
     
    toysoft, Aug 26, 2018
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  5. VetallRX

    VetallRX New Member

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    Very interesting: the text in the terminal runs as if it were some boot loader. But still some rubbish, crossed out different RS232 speeds, and different terminal applications.
     
    VetallRX, Aug 26, 2018
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  6. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    In that case I would replace the rs232 chip, just to be sure that it not creates this issue.
     
    Johnny B., Aug 26, 2018
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  7. VetallRX

    VetallRX New Member

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    OK! But I do not have such a chip. So I'll try to connect the data cable USB to RS232 on FT232.
     
    VetallRX, Aug 26, 2018
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  8. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    Not sure what you planned to do, but the rs232 chip is placed on the motherboard, the U17.
    Also, for a real and proper readings from the serial port you need to use a null modem cable and a serial db9 pins connection to a computer.
    Working with a rs232 to usb cable may give also garbage instead of readable data.
    But not always, some usb to serial cables just works fine for receiving the data from the board, only the writing often not works.
     
    Johnny B., Aug 26, 2018
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  9. VetallRX

    VetallRX New Member

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    I will connect before U17, that is, right up to the CPU tires RX and TX
     
    Last edited: Aug 26, 2018
    VetallRX, Aug 26, 2018
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  10. VetallRX

    VetallRX New Member

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    With the help of an oscilloscope, he checked the work of quartz. For Y3 there was no generation, missing and washed out. Also missing and washed out C2 and R105, there were traces of soldering. Connected terminal, on 115200 trash, switched to 56000 and the text appeared.
    Then rebooted the receiver and again the garbage went to the terminal.
    But how much did I understand, is the CPU alive?
     

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    VetallRX, Aug 27, 2018
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  11. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    Yeah the cpu seems to be alive.
    Based on the Second stage loader wasn't found....
    you need to upload the bootloader and image file which is suitable for your simcard you use.

    You could try it with dreamup, however for that, you need to have a working network and rs232 connection.
    Or try to solve it with Optiflasher, the bootloader fix.

    But still, it succeed only if you know that the box is a original, or clone box and only with a good working network and a real comport connection, and using the correct bootloader and image file, suitabe for the sim card you use.
     
    Johnny B., Aug 27, 2018
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  12. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    As for the Y3 crystal, this I need to check later because at this moment I'm not sure if it's active while the box does not starting up.
    It could be that this crystal is defective, or due some connection issue to/from the cpu.
     
    Johnny B., Aug 27, 2018
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  13. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    As for the Y3 measurements,
    The 1.1v voltage should be present. even after the second stage error.
    By ohm measurements between the ground and the Y3 pins it gives something as 180.1/205.7 k ohms.
    If one of the pins has no value, then it could be a interrupted cpu pin connection.
    If one of the pins is shorted to ground, then it could be caused due a defective ceramic cap.
    If it has the ohm values both side, then it could be a defective crystal.

    When this Y3 crystal has been removed, it gives 1.2v on both sides, the terminal readings are readable, board seems to start up, but my test board has some kernel issues thus it is not fully tested without this crystal.
     
    Johnny B., Aug 28, 2018
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  14. toysoft

    toysoft Well-Known Member Staff Member

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    Johnny,

    Just be sure first that he uses the right parameters, and for example Putty as a terminal (COM Port), and it's the right port, as if any parameter is wrong, naturally it will show wrong data.

    TS


     
    toysoft, Aug 31, 2018
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  15. VetallRX

    VetallRX New Member

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    The parameters in the program do not change, except for speed. Then turn on the power, sometimes the terminal writes normal text, sometimes trash. This is the hardware problem most of all.
    RS232 chip is normal, I dumped it. Connected the USB-RS232 adapter to the CPU. There were the same symptoms.
     
    VetallRX, Sep 1, 2018
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  16. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    Yeah well, I think, check the Y3 measurements.
    Nevertheless, to me it seems not be responsible for the terminal garbage output and thus there is something more wrong, somewhere.
    Still thinking of a defective rs232 chip, or else you use not a real com port on the computer side and not using a wxp operating system.
    Uploading a boot loader etc, can only be done with a real comport, and using a windows Xp operatings system.
    These dm800hd motherboards and the use of tools, are all based for using the wxp and a real comport, not for using a usb to serial cable and other operating systems.
     
    Johnny B., Sep 2, 2018
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  17. VetallRX

    VetallRX New Member

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    I tried on a laptop with windows xp and hardware com port, the symptoms are the same. I will look for y3, it's a bit difficult to find it. In parallel, capacitors will be replaced in voltage stabilizers. There is also a CPU in stock. If there will be any success I will obey.
     
    VetallRX, Sep 3, 2018
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  18. VetallRX

    VetallRX New Member

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    Hello!
    At what standard speed should RS232 port in the tuner work?
    I have 56700, maybe DreamUP does not want to see him.
     
    VetallRX, Sep 28, 2018
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  19. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    Terminal settings are,
    Com.. 1
    Bps.. 115200
    Dbits.. 8
    Par.. no
    Data.. Hardware
     
    Johnny B., Sep 28, 2018
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  20. VetallRX

    VetallRX New Member

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    Probably a problem in Y1. I dropped it out, wiping the board and sealing on the lining. Now there is no garbage in the terminal, but at a speed of 57600. I'm testing a few hours.
    I do not find in stores to buy a new Y1.
    I also replace some capacitors, but they have sent large sizes and 4700uF*10v are not placed, so they have not changed yet.
    Also, definitely the oled display is curtailed. Maybe someone knows its marking?
     
    VetallRX, Sep 28, 2018
    #20
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