No SCART/DVI output

Discussion in 'DM800HD Hardware troubles and Repair support.' started by Jay Santos, Mar 15, 2016.

  1. Jay Santos

    Jay Santos New Member

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    Hello, i was wondering if anyone could help me...
    my dm800 is working but i have no video signal out , any ideas ?
    diferente cables have been tested, also as diferent tvs, :confused: :mad:
    i think that must be something wrong with the hardware.

    thanks in advance.
     
  2. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    Hi,
    I have this defect experienced a few times, and resolved.
    But since it was long ago, I have to look it up in my notes.
    But I think It could be a bad resistor, or transistor or bad print track.
    However, It could also be due the cpu, bad solder contact or a damaged cpu.

    In any case, you will need to measure some parts on the underside of the motherboard to find out what it is, or could be, and you will need a good multimeter to figure it out.
    If you have that, and also can work with it, then I will give you later some measurement information.

    And, it's better if you give a little more information, such as the motherboard version you have.
     
  3. Jay Santos

    Jay Santos New Member

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    Hi, thank you for your reply,
    the motherboard is REV J, and i think the dm800 is a original one.
    I bought it very cheap with a defect but the described problem was NO CA FOUND(well, not anymore).
    I don't have a multimeter but i will buy one today,
    i have noticed there is a componente missing,..U11... but as far as i read, that is needed for somekind of usb...
     
  4. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    Okay, yes Rev J is well known by me, and yes indeed, the U11 is for the two Usb ports on the back, mainly to feed the 5v.
    If you use a usb hub with his own power adapter then these ports should work, even without the U11.

    But to come back to the Dvi port..
    How did you have test it,
    With a monitor with a Dvi port.
    Ot with a cable, Dvi to Hdmi to a tv set.
     
  5. Jay Santos

    Jay Santos New Member

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    Hi, i've tested it with DVI to HDMI, and SCART on two diferent tvs.
    A second DVI to HDMI cable was also tested.
     
  6. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    Okay, I asked this because an HDMI to DVI cable may be faulty, as well as software that is not properly may cause it.
    And because I experienced that someone had wrecked a good working box, because he thought it was a hardware problem on the motherboard.
    Later he noticed that the HDMI cable was faulty.

    But give a sign when you have a multimeter, then we can go further.
     
  7. Jay Santos

    Jay Santos New Member

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    hello, I allready have one :)
     
  8. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    Okay.. in that case I give you Saturday some ohm measurements information from the Dvi.
    In rare cases it could also be due the scart section, but this is only if there is a interruption between the U20 center pin to the R197/R181, which is rare.
    Nevertheless you could check this, just to be sure.
    See this drawing, https://jb8a8f8.com/support/index.php?attachments/dm800-rgb-drawing-jpg.319/

    And just in case, also check the main voltages, but be careful with measurements, do not make a connection between two pins.
    https://jb8a8f8.com/support/index.php?threads/p5-fault-finder-pinout.13/
    I have my + probe from my multi meter equipped with a thin needle.
     
  9. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    I have made a new measurement of the Dvi pins.
    See if you measure a issue.

    dm800hd-dvi-vdc-ohm-measurements.jpg
     
  10. Jay Santos

    Jay Santos New Member

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    Hello, I am no expert with electronics, but what i could see so far is that there are no values between F1 Input and the resistors 281 and 282, also as the Output to pin 14...
     
  11. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    These ohm and vdc measurements are done between the ground, and the measuring point.
    And so, black probe on one of the screw holes from the motherboard, and with the red probe the measurements.
    Ohm measurements are done without powering up the motherboard, so leave the power supply disconnected from the motherboard.

    But about your findings related to the F1 fuse.
    The F1 fuse is a automatic fuse, but should just be measured as if it's a fuse.
    If you measure only the fuse with ohm measurement you should normally see 000 on your display, if it's only one zero (0) then the fuse is bad.
    Basically the same if you put the red and black probe together, then you also see 000 ohms.

    If you do not mean the Ohm value, but that you have there no 5v then forget the above.
    And tell me if this is the problem, the missing 5v.
    But be sure if this is so, you need to measure the DC voltage between the ground and the measuring point.
    And you multimeter must be set to dc voltages.
    However it's saver to measure it by ohm, so that you do not have the risk to damage something.

    If you don't know how to set the multimeter on Ohms, or vdc voltage, give me the type and brand name information from your multimeter, then I can give you the settings instructions.
     
  12. fulvion75

    fulvion75 New Member

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    Hello Johnny, i was really interested in this thread but sadly it didn't come to a result.
    First of all thanks for all the valuable informations found in this forum, great job really :)
    i'm experiencing the same problem with a mother board rev L, no dvi or scart output at all.
    i've checked both outputs in two different tv/monitor. unfortunately i dont have a chance to test another dvi cable, but im pretty sure it works, at least it does using my laptop. since my tv and monitor have only VGA input, im using a DVI to VGA adapter.
    i've made the measurements following your schema and im posting here the results.
    the main differences i've found are:
    1) Ohm measurements on D10, it should be 5.47M but i read 1.2M. regarding this, my multimeter has an upper limit of 2Mohms. i was expecting to read 'out of scale' value.
    2) Voltages on D9 and R281.
    Other differences seems minor to me, but i could be wrong.
    what do you think?
    thanks in advance for any help you could give me.
    Regards,
    Fulvio
     

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  13. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    Hi.
    The 1.2M (normally 5.47M) could be due your measuring device and is basically a direct connection to a cpu dot.
    But the value may also be lower due the D10 which is a 2SD1383K NPN
    By doubts, remove the D10 and measure this again.

    But, because both failed I always first check the U20 center pin connection to the R197 if it's not interrupted between them.
    More about this see this drawing.
    Also check the resistor value (100 Ohm) and the inductor L22 and the R198 0 ohm resistor if they passing true.
     
  14. fulvion75

    fulvion75 New Member

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    Hi Johnny thanks for your quick reply.
    U20 center pin results connected to R197
    R197 measures 75Ohm, not 100
    what you mean by passing true? i measured almost no resistance between their pins for both. L22 1.2Ohm, R198 0Ohm (zero). did i do it well?

    when you say remove D10 you mean to unsolder it? i don't know if i have a so thin tip for my soldering iron. any other way to do it? :)

    i noticed that solderings of DVI connector, SCART, tuner (lets say any soldering that is not part of an SMD element) are dark, oxidated. Do you think it would worth a try to 'refresh' them?

    thanks!
     
  15. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    Q: passing true
    A: Just as a fuse, if it's not interrupted, mainly smd resistor (R) parts with 000 or 0 printed on it are bridges and can just as a fuse become interrupted.
    (L) parts are inductors (coils) and could be internal burned and so become interrupted.

    Q: D10 removal
    A: Forget this, I thought it was connected to this circuit but as the picture shows, it's not connected to the D10.

    Q: oxidated solder
    A: it's always better to refresh outdated solder.
     
  16. fulvion75

    fulvion75 New Member

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    yes, i confirm they are both working and not interrupted.
    at this point ill refresh all solders and let you know if something changed.
    thanks
     
  17. fulvion75

    fulvion75 New Member

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    i refreshed all solders, but i think things got worst... ive been really carefull (i swear!) but now when i power it on, oled remains black and the front red led blinks fast then stops.
    sigh!
    i checked the main voltages following your schema. they are all present
    Johnny please help! hehe :)
    thanks

    Edit:
    turns on, the red led blinks fast then stops. after a while it starts blinking again
    5V on simcard pin 1 are present
    same voltage on both pins of crystal Y1
     
    Last edited: Apr 6, 2017
  18. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    I think, to see if you have made somewhere a fault, take a picture of the print side and maybe I see the reason why.
    Or, connect the motherboard to a serial port and see with a terminal program as putty or windows hyperterminal if there is some life in it.
     
  19. fulvion75

    fulvion75 New Member

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    here it is Johnny. Actually i dont have how to test the serial connection sorry.
     

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  20. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    Picture is good enough, but there is not any reason to see on it why it does the symptom you describe.
    If I must think what it could be than I think of a crystal solder (this are the 3 metal things around the cpu, Y1/Y2/Y3).
    Re solder them if you already have touch them with a solder iron.
    And the U18 may also give this symptom, however only if there is some short between the legs.
    Other option is do the same solder job as you did before, if you can remember what you have done.

    As for the serial check.
    You need a computer with a nine pins serial connector and a serial null modem cable with two db9 female connectors.
    The wiring for this is,
    Pin 2 to the other side pin 3
    Pin 3 to the other side pin 2
    Pin 5 to the other side pin 5
    And the connector metal (Ground) also to the other side.

    As this picture,
    Null Modem.jpg

    Or, if you do not have a computer with this connector, but mostly only usable to use to receive the data from the box and not usable for uploading a image file with the serial method, you can also use a usb to rs232 serial null modem cable.
    rs232 to usb cable.jpg
    But be beware, there are allot different cables, you need at least the Usb to db9 Female version.