highband an bcm4505 tuner

Discussion in 'Hardware troubles and Repair support.' started by rtznfrtz, Apr 10, 2019.

  1. rtznfrtz

    rtznfrtz New Member

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    my tuner is not working on the high band - 11700 (and up) H
    low band H and V and high band V is OK

    any information on what might cause this and which parts are in use for the highband H ??
     
  2. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    Sorry, but no clue because I have never repaired this kind of defects with a bcm4505 tuner, I just replace it.
    But, I often only replace the U7 LNB chip, which often solves some issues, and if not, then I mostly replace the tuner.
     
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  3. Aliraza63

    Aliraza63 Active Member

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    Once I had this kind similar issue with my dm800se sim2.10 in 2014 or 2013 at Hortbird 13 east tp 10719 . I had discussed with Johnny in those days at ferrari forums . he had sent me the tuner diagram . I had replaces the caps which were doubtful.
    after replacing them box worked fine .
    in this pic see the blue circled caps were replaced with the same value but good quality.

    TUNER.JPG

    Try it may be it can work with u to .
     
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  4. rtznfrtz

    rtznfrtz New Member

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    Thx very much - gave it a try and exchanged them all - but no luck this time - still the same issue - no high band H
     
  5. Aliraza63

    Aliraza63 Active Member

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    Which type caps u have used low quality will not effect any more its my tested method
    I had used this kind high quality with hi temperature caps during that test it worked.

    caps.jpg
     
  6. rtznfrtz

    rtznfrtz New Member

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    i used the same cap's as the ones used on the tuner - and i measured the capcity of the removed ones with my meter - non of them was really with an off value - anyway i replaced them - but no change at all (as i already expected after measuring the desoldered caps)
    from a temperature point of view - they had anly 2 minutes so - no time to get them in a high range temperature ;-)
    but anyway - thx for the information
     
  7. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    Just a thought, maybe the crystal Y1
     
  8. rtznfrtz

    rtznfrtz New Member

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    .. as all the other ranges (lo V, lo H and high V) are working, i don't think so (high V also adds the 22khz signal)

    but i'll give it a try, just in case ........
     
  9. oksol

    oksol New Member

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    Try to turn on the increased voltage option
     
  10. rtznfrtz

    rtznfrtz New Member

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    thx, that's what i was starting with.
     
  11. rtznfrtz

    rtznfrtz New Member

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    finally i replaced the LNB 21 chip - and it's working again! post #2 already contained the right answer :)
     
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  12. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    Good to know that this problem may be solved by replacing the lnb chip.
    Thank you for sharing your solution, which may be useful to other members who experience this issue. :)
     
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  13. tinoco

    tinoco Member

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    hello guys can you tell me where is the LNB 21 chip in this tuner because I have a similar problem in my dreambox 800 if the tuner works well but after a while it starts to lose the signal any help thanks,
     
  14. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    You can find the LNBH21PD chip on the print side..
    [​IMG]

    But be sure that the pcb to the motherboard connector is clean before thinking to replace the chip.
     
  15. tomgr

    tomgr New Member

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    Hello!
    I would like to ask a question.
    Can the LNBP21PD be used instead of the LNBH21PD or does it not fit?
    Thanks!
     
  16. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    Q: LNBP21PD instead of LNBH21PD,
    A: The LNBP is older (2002) than the LNBH (2004), but they are basically the same and should/may work If it looks the same based of the datasheets.
    But I can't say 100% because I'm not sure if I had done this before.