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Samsung LCD monitor slow to start up (Crystal aging?)

Discussion in 'Electronic Repair' started by Richard Thomas, Feb 23, 2007.

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  1. I am trying to fix a 4-year old Samsung SM171P (aka GH17P) LCD monitor that can take
    several minutes to achieve initial synchronisation to either VGA(DSUB) or DVI inputs
    - it just sits there alternating its power light orange/green. Once sync is achieved
    it works fine.

    I have the service manual / schematics and have been probing around the main PCB. I
    believe that the problem is that the monitor struggles to get past the point where
    the main GM5020 graphics processing IC measures incoming HSYNC/VSYNC frequencies and
    tries to match them to a mode that it supports. I'm hoping its not the GM5020 as that
    is a PBGA package so can't be replaced by hand.

    I am wondering if the problem is that the crystal frequency has drifted as it ages -
    I see from the parts list that the crystal is unusually fine tolerance 30ppm:
    CRYSTAL-SMD;24MHz,30ppm,28-ABX,16pF,50ohm

    Anyone had similar experience with crystals / Samsung monitors / GM5020 IC?

    Anyone know of companies in the UK that can supply specific made-for-Samsung
    components? (The equivalent of partsearch.com in the US?)

    All help appreciated,

    Richard
     
  2. Mike Berger

    Mike Berger Guest

    Crystals are very reliable, and in this case the drift would
    not be enough to take minutes to sync. It sounds a lot more
    like a component that fails when too cold or uncharged.
     
  3. Guest

    Guest Guest

    sounds like a crappy capacitor somewhere.
     
  4. JANA

    JANA Guest

    Get an ESR meter, and check all the caps in the monitor. You will most
    likely find some that are high in ESR.

    As for having any proprietary parts for your monitor, they will be very
    difficult to find.

    --

    JANA
    _____


    I am trying to fix a 4-year old Samsung SM171P (aka GH17P) LCD monitor that
    can take
    several minutes to achieve initial synchronisation to either VGA(DSUB) or
    DVI inputs
    - it just sits there alternating its power light orange/green. Once sync is
    achieved
    it works fine.

    I have the service manual / schematics and have been probing around the main
    PCB. I
    believe that the problem is that the monitor struggles to get past the point
    where
    the main GM5020 graphics processing IC measures incoming HSYNC/VSYNC
    frequencies and
    tries to match them to a mode that it supports. I'm hoping its not the
    GM5020 as that
    is a PBGA package so can't be replaced by hand.

    I am wondering if the problem is that the crystal frequency has drifted as
    it ages -
    I see from the parts list that the crystal is unusually fine tolerance
    30ppm:
    CRYSTAL-SMD;24MHz,30ppm,28-ABX,16pF,50ohm

    Anyone had similar experience with crystals / Samsung monitors / GM5020 IC?

    Anyone know of companies in the UK that can supply specific made-for-Samsung
    components? (The equivalent of partsearch.com in the US?)

    All help appreciated,

    Richard
     
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