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No vertical scan

Hi Robotek,

Does the info that I just added about working OK after being off point more likely to the vertical IC, the various capacitors, or the yoke connection?
What exactly did you mean by dry jointed? Did you mean that some of the solder connections might be cracked or have flux buildup?

Posted by on

  • msternx Jul 02, 2008

    Hi Robotek,

    In response to your July 2nd comment, I have not been able to

    see any of your comments since June 30 th.

    Also, there is something wrong with the rating system, because

    I had clicked the rating "helpful", not "thanks for trying".

    I would still like to see your latest comments.

    The last entry in the string that I can see is from Maklean,

    who provided a most useful piece of info---the site to

    download the TV service manual.

  • msternx Jul 09, 2008

    Hi Robotek,



    Your info has been great. Because I have been out of town

    on business, I haven't been able to get at the circuit board.

    I will get back to you with the results shortly.

×

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  • Master
  • 1,512 Answers

Yes, it is likely that it is dry jointed,as Premtech described, a ring like crack about the joint where it solders down to the printed circuit. They are generally pretty obvious. There is generally no flux on modern PCB's If you cannot solder,then this may pose a problem. What are your skills like with an iron in hand? :)

Posted on Jun 30, 2008

  • 2 more comments 
  • Graeme Ross
    Graeme Ross Jul 02, 2008

    I have posted some more information to the original post.Are you still able to see it here

    I notice that your rating of my solution is thanks for trying, you have indicated that you would like to proceed with my guidance, a change to FixYa on that post is then appropriate. Cheers

    robotek


  • Graeme Ross
    Graeme Ross Jul 04, 2008

    I will repost to here. I have the service manual for you also, but a free version. I have cut and pasted my efforts into here. Sorry bout that. Didn't know you couldn't see the post still.





    yes, the fault may be marginal.
    Capacitors are a likely cause of this condition also. I generally just
    rebuild the area, clean old heatsink paste away, and use new compound.
    I use 2% silver content solder for its better heat stress strength

    Comment by robotek, posted on Jun 30, 2008
    DON'T FORGET - DANGEROUS VOLTAGES ARE PRESENT
    even with power disconnected !!! Be sure to Work electrically safe.




    Comment by robotek, posted on Jun 30, 2008If
    the problem comes and goes however, it is probably more likely to be
    dry joints. Start with resoldering first, then if it does not improve
    capacitors and vertical IC would be my call


    Comment by robotek, posted on Jun 30, 2008
    Here is another repair method relaying the same message about the verticle IC by one of our Top Experts, Premtech

    it's most likely the the vertical IC an
    LA7847-E has probably become ring-cracked at the point where the pins
    are soldered to the pc board.

    Depending on how long it has been
    allowed to arc the IC may have failed also, but they are not terribly
    expensive or difficult to repair - at least not here in the shop.

    The
    main board has to be removed. Locate the vertical IC - it will be
    mounted to a metal heat sink and the IC will be stamped LA7847. Then
    turn the board over and inspect where the pins are soldered to the foil
    side of the board. One or more will look ring cracked or fractured all
    the way around the pin. At this point you have two options, carefully
    reflow solder over each pin and put it back together or replace the IC
    by de-soldering it and removing it from it's heatsink. remember to use
    a good heat sink grease when applying the new IC.. There should also be
    a couple of caps in pretty close proximity to that IC... One should be
    about 50v/100uf and in the shop here we test em all... You might also
    just replace that one for good measure - they're not expensive either...




    Comment by robotek, posted on Jun 30, 2008it
    can be said that there are many ways to skin a cat, there is only one
    way to skin this one. The solutions given relating to the verticle
    output IC are correct. I hope that the extra solution I provided from
    Premtech helps clear that up. Cheers


    Comment by robotek, posted on Jun 30, 2008@midwest. the LA1460 is a low power dip chip... not a vertical output chip. What part of the circuit are you looking at?



    Comment by robotek, posted on Jun 30, 2008
    no
    problem glad to be of help. The chasis generally slide into rails on
    the front section, and also into the rear casing. It is not hard to
    manouver it about to get access to the verticlechip. They slide out and
    with not much "unhooking" of loom dress, you can turn the chassis over.
    Will post back to here tommorrow. Cheers

    regards
    robotek




    Comment by robotek, posted on Jul 01, 2008
    ----When the picture becomes a horizontal line, I can get the picture back by turning off the TV and
    turning back on after several minutes. It will then operate for 5 to 10 minutes before failing....

    Sounds
    like you are talking about an intermittent fault. This is classic
    behaviour for heat stressed dry/cracked solder joints about the
    VerticalOutput chip. The chip may even be desoldering itself from
    overheating in the first place, the conditions promoting the
    overheating being caused by failing overheated, vented out caps mounted
    near the heatsink.

    Have you got to the chassis yet?





    Comment by robotek, posted on Jul 01, 2008To help a little with the repair provess, I have found a link so you can download the service manual for the 32DF46.
    Is the 32 inch version of the set you have, but same chassis i believe.
    The LA7847 comes up for both models, so the vertical circuit will be
    relatively the same. It is marked as IC401,and is towards the center of
    the main board near the flyback (eht) transforme.

  • Graeme Ross
    Graeme Ross Jul 04, 2008

    So download the manual. and do some sight checks with your chassis to see if they are indeed the same. Then you have a reference point that we can work from together :)

  • Graeme Ross
    Graeme Ross Jul 05, 2008

    How did you get on with the set? :)

×

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hi,
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