8000HD Tuner related measurements

Discussion in 'Schematic drawings, Pcb images etc..' started by Johnny B., Aug 29, 2015.

  1. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    If you have a problem with the tuners than I have here some measurements which maybe could helps to find your problem.
    However, always check the power supply before you going deeper in the tuner issues.

    Good luck..

    Several tuner slot measurements, with the 5v for onboard tuners.
    Dm8khd-tuner-vdc-info-v2.jpg

    !2v circuit overview, for the on-board tuners see K/J and tuners slots H/G
    Dm8000hd-pcb-12v-circuit.jpg
     
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  2. ham73

    ham73 New Member

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    Dear Johnny,
    THANK YOU !! Very HELPFUL !

    All DC voltage are same - specially in the power supply also on my DM8000

    After cleaning all satellite list and several restart - FINALLY - TUNER B is working OK ! I didn't plug in Tuner C - I am testing it step by step....
    BUT
    Tuner A is dead !!! Do you have more measurements for the Tuner A - What can be burned out after the coax shortcut for more then 1 day.... Any idea if there is a DC bias or something similar for the 12/18 V for the LNB. Where the 18V is generated?
    Best regards, Mike
     
  3. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    The brain that is responsible for the 12/18v is the SL6423B chip, see the datasheet for more info.
    dm8000hd-onboardtuners-isl6423b.pdf

    However it's protected against cable short circuits but I had one case that it was defective.
    I think, check the 12v vcc input, or compare the values with the working side.

    Most safest is to disconnect the power supply and measure the values with ohms.
    Measure the value between the ground and the point of measurement.
    Compare this value with the other tuner side.

    But I think, if there is a problem than it's most likely a inductor, or 0 ohms resistor interruption.

    But it can also be a coil interruption, as under the cover of the LNB connection.
    SAM_1600.JPG
     

    Attached Files:

  4. ham73

    ham73 New Member

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    Could you PLS post a photo under the cover of the LNB connection - any info about the DC bias inductor?
     
  5. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    Uhm, this is already posted, see this image which shows what's under the cover from the two on-boards lnb connectors.
    http://jb8a8f8.com/support/index.php?attachments/sam_1600-jpg.208/

    DC bias inductor info, If you mean inductor uH values, than I can't help you.
    Voltage or ohm values is possible, but not soon, maybe the coming weekend.
     
  6. ham73

    ham73 New Member

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    I am sorry for a missing of understanding - I have the picture under the cover, but I would like to see the picture with some DC measurement info from the bottom side of the PCB close to the LNB A/B - F connectors (not under cover...)
     
  7. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    No idea why you asked that because there is almost nothing to be measured on the print side.
    And certainly not under the LNB connection section, which is mainly ground shielding.
    This you can see on this print side image, http://postimg.org/image/wavfeuvq7/
    And for extra also a image of the parts side, http://postimg.org/image/wf6a923fj/

    Remember that the PCB has more than two layers, probably four layers.

    But sorry to say, I can not help you with measurements from the print side, because than I have to disassemble a complete fully working DM8000HD, but also, I do not see the point of it.
     
  8. ham73

    ham73 New Member

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    Dear Johnny,
    I deeply appreciate your help. There was no intention to dissmantle your DM8000HD - I was just thinking that in case you have more pictures and measurements .
    Thank you for all!
    Mike
     
  9. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    Yeah I have more notes of it, but mainly on paper.
    But for the record, Do you have the main voltages for the on board tuner A, and do you have some voltage out on the lnb tuner A output?

    One note, it's only possible to get some voltage measurements on a tuner if you have set it up, and set on a channel.
    So, if tuner A is not been configured, and set on a channel, it will not give any voltage output for to the lnb.

    Furthermore, I have here a overview of some ic's that relate to the on-board tuner.
    It at least shows what its functions are.

    dm8khd-tunerparts-description.jpg