resistance value on vu duo2

Discussion in 'VuPlus Duo2 Hardware troubles and Repair support' started by bjt01, Nov 13, 2020.

  1. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    The voltages depends on the output it gives, it must always higher than the output voltages, in this case it is 3v, thus all above is fine.

    The smd size number is I think 0102, more about it you can see here..
     
  2. Piotrekop

    Piotrekop Member

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    This size and this capacitor is hard to buy. It will be hard to get hold of.
     
  3. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    Yeah well, without it the board should still work.
     
  4. Piotrekop

    Piotrekop Member

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    Do you advise to leave them or connect these pins?
     
  5. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    I assume you still talking about one small cap.. then..
    No, do not connect it, you may create a short circuit to ground, just leave it.
     
  6. Piotrekop

    Piotrekop Member

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    @Johnny B.
    I have already replaced all capacitors in duo2. Initially, the white led was still on. While taking measurements with the meter, the duo2 booted up and worked. My joy was short-lived. After screwing and completing all the screws of the duo2 housing, it lights up in white again. Strange because it was turned off and on several times and it worked.

    I wanted to check the resistors in the U702/U825 chip, but they are not under the name you give in the guide. How can I find it?

    Are all capacitors always energized? While the white LED is on, a few capacitors are de-energized. Maybe I overheated them during the replacement.

    I did all the voltage and resistance measurements in my duo2.

    Can I ask you to verify my duo2 voltage and resistance measurements? I marked my doubts in the measurements with question marks and exclamation marks. The tensions are probably good. It is worse with resistance.

    It's about the U103 U809 chip and TP data. I think there is a short circuit to ground.

    Can you check it out? Maybe I missed something.

    The measurements are a bit different because the power plate and the faceplate are not disconnected.

    Thanks again for your help.
     

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  7. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    When I read...
    1. While taking measurements with the meter, the duo2 booted up and worked.
    And...
    2. After screwing and completing all the screws of the duo2 housing, it lights up in white again.

    Than it seems to me a bad solder that when measure on it fixed it for a short time.
    It could be a bad soldered smd part as maybe a resistor.

    As for the U809 seems to me okay but the U103 seems to me a bit suspicious.

    Rechecking these measurements, that I could probably do not earlier than on Wednesday because then I may be in my repair cave.
     
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  8. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    I have rechecked my measurements which are noted on the picture, as also only the motherboard without any connection to/on, and they are without any differences as already given.

    Thus, based that it started up by/when doing some measurements, I'll keep it on a bad solder connection.
     
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  9. Piotrekop

    Piotrekop Member

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    The white led is also off. Lost power on motherboard. There is only 12V on U815, U702, U825, U824, U823 chips. I checked all soldering points with a meter and reheated all soldered connections with a soldering iron. No effect.
     
  10. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    No front led should not be so hard to find the reason why it not showing.
    Maybe the front-panel, the flat cable.
    Or a dc to dc regulator with a 12v input, and a 5v output failed, then it may not activate the other dc to dc converters with the results of also no front led.

    Further, be always a bit carefully with heating up parts with a hot air gun, too hot could damage a chip/ic etc. and even the pcb board such as the inner layers.
     
  11. Piotrekop

    Piotrekop Member

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    The white LED glowed and went out before my eyes. I checked the solders and there is a current transition and connection everywhere. The flat-ribbon cable is rather ok because I replaced the front panel. There may be a similar problem as in solo2 - I wrote a post. I don't know if you read
    How to check the errors you wrote about?
     
  12. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    As for this issue, I;m starting to think that it may be a cpu issue, or related to it because the white led activity may related too it.
    Sorry to say but, I have further no ideas to help you further with it, I'm afraid that this box is no longer repairable.
     
  13. Piotrekop

    Piotrekop Member

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    Maybe the error is similar to the one in Solo2? Suddenly the tension that was there before disappeared because Duo2 worked.
    Which chip gets the current first?
    What would you start with?
    I have already done too much work on it so I would like to fix it. Now there is a problem with the power supply. There is only 12V on the motherboard. Maybe follow the same lead as in Solo2?
     
  14. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    Not right, the solo2 depends totally on the front panel, without it, it can not work.
    The Duo2 can work without the front panel.

    At this moment I can not tell if, and which dc to dc step down converter could be a main voltage for the lower ones, but logic could be the one with the 5v output because its logic that regulators lower than 5v may feed with it instead of a 12v input.
     
  15. Piotrekop

    Piotrekop Member

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    Currently there is only 12V and there is no voltage control. Maybe there is also a voltage regulator failure?
    You wrote that you do not like the resistance of the U103 chip. Maybe it's actually his fault?
     
  16. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    As for the U103, by doubts, I think you can remove it and see if the other voltages come back to life.
    Be aware that when it do, it may probably wise not to power it up to long.

    Further, check the 12 to 5v regulator, thinking the u803 which is close to the flat cable/front panel.

    Maybe I can find tomorrow some time to check which ic's needs the 5v to run and which ones uses the EN pin to power on.
     
  17. Piotrekop

    Piotrekop Member

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    it would be great.

    To remove the U103 chip, which soldering station do you recommend? Hot air soldering iron or traditional soldering iron. At what temperature it is best to do it so as not to overheat the elements.
     
    Last edited: Jan 4, 2021
  18. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    U103 chip, leave it as it is because somehow it seems to be good.
     
  19. Piotrekop

    Piotrekop Member

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    So I wonder if the lack of the C820 capacitor did not cause further damage to the duo2 motherboard and consequently it does not work.

    You don't know which circuit gets the first current and controls the rest of the circuits? Maybe a search similar to solo2? I know it's a bit different with the front panels, but the current control is similar.

    You don't know exactly what parameters this capacitor has? I checked the internet and these C820 parameters are unattainable.
     
    Last edited: Jan 4, 2021
  20. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    C820, I assume it's a ceramic cap, but I have no idea were it's placed.
    But when there is a second one placed or more on that same circuit area, then you may assume that they have a same value.

    As for the "which circuit gets the first current", all voltage regulators has the 12v input with exception of some.
    Thus if they all being inactive, and has the 12v input, than they are probably switched off by the EN pin.
    As for the input voltages I have noted on this picture, but since it become pretty messy to use, and has no good overview of the in/outputs, i need to make a better one in the future.
     

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