Question about Samsung HCL4715W 47" Rear Projection Television

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Internal Screen Adjustments No Response

My Samsung HCL4715w rear projection had a convergence problem. I replace the SUB PCB. Convergence problem fixed. However, Red CRT is very dim. I tried the screen adjustments directly on the CRT, but no response. Same for Blue and Green (think they work in series). Any cheap fixes or ideas? Definitely not putting a new Red CRT on - set is not worth it. But I would love to tinker and get this set fixed, just for the satisfaction of completion. I am not electric technical, but if I can do surgery on humans, I should be able to do surgery on a television.

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  • Mark Koonce Sep 06, 2007

    screen controls wires, directly go to the Red CRT, then jumps to green, then blue.

    Focus controls go directly to the focus block.

    Focus controls work, but the controls on the CRT have no response, and red CRT is dim.

    Someone mentioned the 220V line?

  • Mark Koonce Sep 06, 2007

    You are correct in regrds to the focus controls.

    But the screen control wire goes directly to the Red CRT, then is in series with Green and Blue.

    Red CRT is dim (Blue and Green are fine). The screen controls on all three have no response.

    Someone mentioned the 220V line?

  • Mark Koonce Sep 06, 2007

    The Focus block has three dials for Focus, and you can clearly see the wires going to the block.

    Then the Screen controls on the Focus block are "dummy switches", no wires going into the back of the Focus block.

    You can clearly see the Screen Controls wire going from the Sub PCB directly to the Red CRT, then it goes over to the Green CRT, and then the Blue CRT.



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Thr focus block assy.has the screen and focus controls on it it about 3"x3" in size has red wires attached to it and one feeding form the flyback transformer to it.

Posted on Sep 06, 2007

  • g w Sep 06, 2007

    you can check on each neck board for the b+ voltage and screen voltage if there the problem is common to all three because you should be able to adjust either one at any time ,not affecting the other if the fault is not common to all,when you tried to adjust the focus did you see 6 adjustment pots on the focus block.



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