DM800HD, USB 4.80 Volt

Discussion in 'DM800HD Hardware troubles and Repair support.' started by Bobo360, Sep 17, 2019.

  1. Bobo360

    Bobo360 New Member

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    Hello everyone.
    Thank you for welcoming me to the forum.
    I have a problem in my dreambox. In the rear USB I installed a turner DTT.

    I found the TV signal problems, but then I discovered that the voltage on the USB is 4.80 volts.
    Where do I begin the tensions controls?
    What are the charge circuitry to generate 5 volts for the USB?
    I read the post, I could understand that they should be U29 and / or U22. it's correct.
    Or U11 with its capacitors?

    Or it fell other tips.
    I assume it is some capacitor which is worn.

    Thanks
     
    Last edited: Sep 17, 2019
  2. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    The U22 delivers the 5v, and the U11 is for protection when shorted, or to heavy load, in one of these situation it should shut down the voltage.
    However these usb ports can not handle a to much heavy load, I think max 1 Amp, but it may even lower as 500 mA.
    Suppose that your DTT usb stick use higher, then you can better choose a extra external usb hub, with his own power supply.
     
  3. Bobo360

    Bobo360 New Member

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    First of all thanks for the reply.
    My USB DTT is a "Hauppauge WinTV Nova-T" (dib0700).
    So it may be an absorption problem?
    I remember that used to work well. Now I have these problems. That erroneously attributed to the images DM800HD.

    The evidence that I have to make is whether, with no USB inserted. That I live on USB.
    Quite right?

    Thanks
     
  4. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    Could be, and the most easiest way to finding it out is to use a usb hub, one with his own power source.
    Or else try to see if you can fix it by measure some parts as the D15-L38 side and when it gives the 5v, the coil L38 output side to see if it's lowered the voltage after it.
    But still, I would see if it solves with a powered usb hub because it can also be another thing as the usb dtt itself.
     
  5. Bobo360

    Bobo360 New Member

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    Thanks again,
    when I put a small HUB fed with a 5.2V power supply.
    When I connect everything, usb hub and dtt the decoder. The voltage on usb is 4,96V.

    you seem?
     
  6. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    Based on this, I get the idea that the dtt decoder use a higher amp consumption than normal, most likely it has some defects.
     
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  7. Bobo360

    Bobo360 New Member

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    How can I verify this? I put a USB with Ampere absorption display. But the absorption is little.
    What can I do? Can I do some other tests? Thank you
     
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  8. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    When a Usb hub, one which has it's own power supply and has at least a 1 amps or higher supply, and the Hauppauge WinTV Nova-T stick still does not works, also not on a normal pc computer, then you may assume that this stick has some issues.
     
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  9. Bobo360

    Bobo360 New Member

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    OK thanks. The further proof that I can do and connect everything in the PC and see if it has the same problem.
     
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  10. Bobo360

    Bobo360 New Member

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    I bought the Sky digital key led blue, (A867). I am currently using it without powered HUB. But even with this I know that I have signal problems. What do you advise me to do?
     
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  11. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    To be honest, I have not the idea that it's caused due a hardware issue, I'm thinking more to a driver, upgrade or other related software issue.
    Maybe someone else on this forum, someone who have some experiences with these could help you.
    Or searching with google to Sky digital key led blue, (A867) may give some more info about it.
    But I do not use and have this, thus I have further no ideas to help you.
     
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  12. toysoft

    toysoft Well-Known Member Staff Member

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    It's possible that the driver is buggy yes... so it would be important to test few different images that have different drivers for that DVB-T USB Key, and see if it changes something.

    TS
     
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  13. Bobo360

    Bobo360 New Member

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    ok, thanks for all the advice. The problem is that changing the USB (from WinTV to A867) is slightly better. But I haven't solved it. The decoder seems to be better when it is restarted recently. After slow down a little. In addition, without the USB turner it is much faster. My next step is to update the Japhar SIM and use another image with new drivers. But my dilemma remains that with both USB DTTs I always have signal and slowdown problems. USB voltage is never 5.22V
     
  14. toysoft

    toysoft Well-Known Member Staff Member

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    Are you sure the 4 big capacitors are OK ? Perhaps end of life for them and need replacement ?

    Check with Johnny.

    TS
     
  15. Bobo360

    Bobo360 New Member

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    Sorry for my photos, it's all in progress. I attach my photos. I use that tool to see the tension.
    The voltage in the USB is 4.88V.
    In the USB of the PC it is of 5.08 at least.
    Johnny's guides explain that those capacitors don't affect USB. waiting for a confirmation.

    I measured in point P8, the voltage is 4.90V with the multimeter.

    [​IMG]

    photo_2020-03-29_16-18-00 (2).jpg

    photo_2020-03-29_16-18-00.jpg

    Thanks
     
    Last edited: Mar 29, 2020
  16. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    FYI, Not that it helps with your problem, but it can help for a longer life of your box by removing all the dust.

    As for the USB voltage, the 5v for both ports is provided by the U11, a max1823 dual USB switch and the main voltage comes from the U22 12v to 5v step down voltage regulator.

    The caps for the Usb are the C204 / C210 and C211 which you can also see on the U11 drawing.

    But still, I'm not convinced that it's caused due the voltages because in normal situation I may not be a big deal to have 4.8vdc insted of the 5v, and also because there may be a 5v to 3.3v step down regulator in these kind of DVB-T USB sticks, therefor it basically works with the 3.3v, and so the 4.8v instead of the 5+ voltage may not be a issue because it still has the 3.3v to work with.
    But still, as I say earlier, by some doubt it's easy to check by using a usb hub, one with his own 5v power supply.
     
  17. Bobo360

    Bobo360 New Member

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    Thanks again for your help support.
    Yes, I will remove the dust.
    I wanted to add you that even without USB connected and in standby the voltage on P8 is always around 4.90V.
     
  18. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    Could be, when the fan is still running in standby, it may reduce this voltage when it's asking a bit more amps than it normally did.
    In any case, these 5v circuit is a bit weak as for the power consumption, but also the U11 can only handle 720mA per channel.

    There are other mods which can improve the usb 5v by using a 2 or 3Amp 12 to 5v dc to dc converter but I can not imagine that these DVB-T stick consume so much power.
    I'm still thinking of a some kind of upgrade, or driver issue, or the box itself has become to weak to handle it.
    Maybe it's a idea to play some hd movies from a usb stick to see if it can handle it, or maybe it's a idea to check if the DVB-T stick works on lower quality channels, but issues gives on high quality channels.
    Other idea is to use a power supply with more Amps, for example a 3 to max 5Amps 12vDc power supply.
    But be aware that the center hole is the positive side.

    And another idea could be to replace the fan for a 12v fan, so that you spare the 5v circuit with it, or use a 12 to 5v dc to dc converter to feed the fan.
    Be also aware that dust into the fan can rises the Amps consumption, same when you hold the fan with a finger, the amp consumption will rise up.
     
  19. Bobo360

    Bobo360 New Member

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    Thanks again for the many ideas.
    Let's see if I can add something.

    1. The USB digital key is 1.1W so about 220 mA.
    2. I use a power supply for the 3A decoder, the one they gave me. Could I use one of 5A?
    3. I try again the only powered HUB that worked, and I'll tell you if there are any changes.
    4. Both with SD and HD channels same problem. It doesn't hang from this. at least I think so. I should try to put an HD movie on a pen and try playing.
    5. Fan, I changed several of them, the "original" one was stuck still, I don't want it to damage the 5V. However this also makes noise. I will try to use a 12 V. Where is a good point that I take the 12V? where I don't bother.
    6. Thanks for your support.
     
  20. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    2. Normally it a 3Amps power supply sufficient for these type receivers, but indeed you can also use a 5 amp power supply.
    5. Be aware that every fan has a different power (amps) consumption, by choosing a to high version, it will weaken the 5v circuit which is not only involves the Usb voltage, but also the voltages for some other circuits.
    By using a 12v fan, you can just connect it to the 12v input circuit, however, be aware that than the fan will always run, also in standby.