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Thread: A1200 - No Blue Colour on RGB

  1. #1
    PARALAX's Avatar
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    Exclamation A1200 - No Blue Colour on RGB

    I need some help! I got an A600 several days ago with wrong colours on RGB-Port due to missing blue. I already replaced all 47 and 68 Ω resistors on the front side on the board behind the RGB-Port and even the both 74HTC244 IC's but no change. Then I interchange the capacitors for the direct RGB output to ensure that they are not broken. After resoldering I find out that the right capacitor (see picture) obvioulsy don't get any signal. If I solder the other ones seperately I get a red or green picture but the right one gives me a black screen only instead of blue, no matter which capacitor I use. So the problem can't come from the capacitors itself.

    Soldering all capacitors as normal only gives me a yellow-brown boot screen as shown in the second picture. I also measure all the connections between the RGB-Port pins and the capacitors with a voltage and continuity tester and they are all okay without interruption, even the blue one. The blue signal must be lost somewhere before capacitors pads but I couldn't find out where. I also measured all the resistors on the front and back side of the RGB-Port and they all have the correct values (but I couldn't measure all the capacitors with my multimeter due to missing function).

    Could any one help me how to trace the signal and find out the reason why no blue signal is coming to the capacitors, even when both 74HTC244 IC's are working? I've run out of ideas currently but I want to give up the board yet completely.
    Attached Thumbnails Attached Thumbnails RGB_1.jpg   RGB_2.jpg  

  2. #2
    resistance is futile! Amibayer! roy_bates's Avatar
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    i suggest looking in the video encoder area or video dac

    test composite as well
    Last edited by roy_bates; 1st April 2017 at 16:38.
    i have got too much hardware,it would only hurt your eyes to look at it here

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    PARALAX's Avatar
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    Problem solved! The CXA1145M did have bad contact due to a leaked capacitor. So I removed, cleaned and resolder him as well as 3 transitors. After reflowing it works again.

    Before:

    Click image for larger version. 

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    Afterwards:

    Click image for larger version. 

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    Last edited by PARALAX; 4th April 2017 at 19:39.

  4. #4
    Ya' Like it Retr0? VIP Zetr0's Avatar
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    Click image for larger version. 

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    Nice =)
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