DM800 SE clone with heated CI U1102

Discussion in 'Hardware troubles and Repair support.' started by dankwilly, Mar 26, 2020.

  1. dankwilly

    dankwilly New Member

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    Hello, this is my first post. I have a Dreambox DM800SE clone (sunray) and started to lose signal from the tuner. I checked the same and found nothing different. I saw the input voltage and instead of having 12VDC it was 7.4V. I fed a regular bench source. I found the CI U1002 very hot. After researching here on the forum I did the voltage measurement on the P1100 connector and find the following voltages:
    Pins:
    7- 0V GND
    6- 0V GND
    5- 4.15V
    4- 1.56V
    3- 2.48V
    2-1.32V
    1-0.3V
    I measured the resistance of L1108, L1109 and R1136 and found the value of 5.36MOhm, where it should be Oohm.
    When the problem started, led D203 was on.

    (Translation by google. I don't speak english)
     
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  2. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    It's not clear to me if you had solved it, or has some questions about this but assuming you have a issue with it...
    This looks to me a cpu issue, but before in/exclude it you can better disable the 3.3v and 1,2v from the 5v circuit by removing the zero ohm resistors R1112 and R1131 from the 5v source L1100/L1101/U1100.
    More about it, see this drawing.
    When removed, measure the 5v side circuit by ohms, see if the ohms value become close to normal.
    If so, then you can
    Also, not sure it may but when both resistors are removed, it may not be wise to add power to the board, you may get more damage to the other voltage regulators.
     
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  3. dankwilly

    dankwilly New Member

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    [QUOTE = "Johnny B., post: 5035, membro: 2"] Não está claro para mim se você o resolveu ou se tem algumas perguntas sobre isso, mas supondo que você tenha um problema com ele ...
    Isso me parece um problema de CPU, mas antes de / excluí-lo, é possível desativar melhor os 3,3v e 1,2v do circuito de 5v removendo os resistores de zero ohm R1112 e R1131 da fonte de 5v L1100 / L1101 / U1100.
    Mais sobre isso, veja este desenho .
    Quando removido, meça o circuito lateral de 5v em ohms, veja se o valor dos ohms se aproxima do normal.
    Se sim, então você pode
    Além disso, não tenho certeza, mas quando os dois resistores são removidos, pode não ser aconselhável adicionar energia à placa, pois você pode danificar mais os outros reguladores de tensão. [/ QUOTE]

    Jhonny, I gave you some incorrect information. The L1108 and L1109 inductors and the R1136 resistor are not open as I informed in the previous post. I made the measurement on the wrong multimeter scale. One more thing I saw today, the Q1111 transistor is heating up too. What does it feed?
     
  4. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    The Q1111 is a NTD4858N power mosfet, in this case a N type and it's basicly a sort of switch..
    If you want to know what it does, then I advice you to google search to mosfet, what does it do.
    There are also good explanations about it on youtube as this.
    With this schematic/drawing you can see what it does, and were it goes.

    When it's become hot, then it could be due a heavy load from it, or the voltages to it is to low.
    In any case, parts which are in contact with the ground could create a heavy load so that the parts connected to it become hotter than normal.
    Since this Q1111, the source pin goes to the Drain pin of the Q1110, and this part has a contact to the ground, then it is possible that this part is creating the problem.
    However, it does not have to be, It could also be caused due the U1103.
    In any case, to know if it's all caused due the Q1110/Q1111 it's better to remove one of then, or at least the one which is in contact with the 5v circuit to see if the 5v circuit ohms value become normal.
     
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  5. dankwilly

    dankwilly New Member

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    Where is the 3.3V line generated from?
    By removing R1112 and R1131 the resistance values on the P1100 pins remained:
    1- 0
    2 - 0
    3 - 918R
    4 - 92,4R
    5 - 3,3K
    6 - 30R
    7 - 300R
     
    Last edited: Mar 27, 2020
  6. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    5v to 3.3v comes from the U1101, output is the coil L1112
    The numbering starts from beneath, thus 7-300R = pin 1

    You have a issue with the pins 3 the 2.5v and pin 4 the 3.3v
    which is a bit strange since both are feed with the 5v, and that circuit seems to have the correct value.
    If I must do a guess,based on this information, then I would suspect the Q1106
     
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  7. dankwilly

    dankwilly New Member

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    I did a test on the Q1106 with the digital multimeter. I disconnected the source terminal and made a direct measurement between drain and source with the digital multimeter and the indication was 0.5V. In the reverse measurement "OL" should appear in the dsplay of the multimeter but it showed a voltage of 1.754V. I think that this mosfet may be leaky
     
  8. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    Its not uncommon that these mosfets become defective, but you should notice some ohms value changes when this is the reason for the wrong values of pin 3 and 4,

    7 - 0
    6 - 0
    5 - 918R
    4 - 92,4R
    3 - 3,3K
    2 - 30R
    1 - 300R

    [​IMG]
     
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  9. dankwilly

    dankwilly New Member

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    From the measurements of the resistance values, I think the 5V, 1.2V and 1.8V line are OK. I think the problem is 3.3V. The resistance value of pin 3 was initially 19.47K, after I removed R1112 and 1131 it fell to about 3.3V. Even coming back both resistors this low resistance continued. I'll check their welds again.
     
  10. dankwilly

    dankwilly New Member

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    Jhonny I would like to replace mosfet Q1106 but I can't find the component to buy. I have here in hand the RF1S45N02LSM, the problem is that it is 20V and 45A. Would it be possible to replace it?
     
  11. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    Hmm, I have no problems with finding them on ebay, searching to 4858NT4G
     
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  12. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    Sorry, this was not your question, but to answer it,
    I always prefer to use the original parts, or at least with the same specs to be sure not to create new/other damages.
    So, basically saying, I can not give you the advice to use it due the differences, and it looks to me that it not can be used.

    But see the datasheets of the dm800se 4858NG and yours
     

    Attached Files:

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  13. dankwilly

    dankwilly New Member

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    O problema é que aqui no Brasil você não encontra componentes eletrônicos com muita facilidade, então você precisa comprar da China. Com a atual crise do coronavírus, as importações são muito caras e demoradas. Se eu pedir hoje, espera-se que seja entregue em pelo menos 60 dias.
     
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  14. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    Yeah I'm aware of that, because I have more than a dozen orders underway from aliexpress/China which were ordered in the first week of February and still not received.
    But when I need it faster, then I ordered it often by Ebay, from sellers of the UK or other country withing the EU.
    Which are often expensiver, but at least to here, the Netherlands faster.

    There are also others, as Mouser, Digikey, Rsonline but it's there much expensive and often only for companies.
    But the delivery time is verry fast, even in this time.

    But, you could of course try the one you have, but I can't recommend it because this is a complicated circuit with a master and slave circuit.
    But when you try, keep an eye to it so that when it's go wrong you can pull the plug.
     
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  15. dankwilly

    dankwilly New Member

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    Jhonny, I removed L1108 and the measurements in P1100 changed to :
    7 - 0
    6 - 0
    5 - 908R
    4 - 2.7K ( previously with 92R)
    3 - 19,4K
    2 - 30,0R
    1 - 263R
    On one side of the L1108 is 2.7Kohms and on the other side 92R. I know that line feeds several sectors. Could you tell me which components usually give problems on this line? Are the Mosfets Q1105 and Q1106 before or after the L1108?
     
  16. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    Not sure if I had figured it out the correct way, but based on my notes is the other side of the L1108 for the network circuits as you can see here.
    It's may possible that the box could startup without the L1108, but I'm not sure of it because it was already a long time ago that I did the dm800se repairs.
     
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