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CRT color TV problem

Discussion in 'Troubleshooting and Repair' started by srijib, Sep 4, 2017.

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  1. srijib

    srijib

    3
    1
    Sep 4, 2017
    I have a weird problem with the CRT tv, it is Samsung Muti Bass. PCB schematic KS3A.

    http://www.e-rusu.ro/scheme/Samsung/KS3A/34228.pdf

    it started with a wrong connection. I fixed the flyback transformer but wrongly connected the CRT ground wire connection to degaussing slot on the PCB. (not knowing)

    it worked without any issue for 3 days. then one evening it banged with a big startup sound, then the screen went complete white. after opening the back cover i realized the wrong connection.

    now it is acting weird, if i take the PCB out, back cover open everything works as normal (but no more startup or turn off beep). the moment i insert the pcb below the crt into the slot it gives white horizontal lines. with no picture. as attached in the image below.
    IMG_20170904_230538.jpg

    when I keep the PCB out, like this it works just fine. Problem is that i can not put the back cover. i doubt is the degauss circuit us gone but looks like it is fine the PTC is also ok. It gets hot when working for some time.
    IMG_20170904_230627.jpg
     
  2. srijib

    srijib

    3
    1
    Sep 4, 2017
    Any help someone ?
     
  3. davenn

    davenn Moderator

    13,812
    1,945
    Sep 5, 2009
    That is showing retrace lines, indicating that the blanking circuit isn't working properly

    which PCB ?
     
  4. 73's de Edd

    73's de Edd

    3,085
    1,302
    Aug 21, 2015
    Sir srijib . . . . .

    Two thoughts :

    You can see that the glass envelope of the bottom of the picture tube gets quite close to some of the top of chassis components when Being FULLY slid forward within the plastic rails into the set.
    Use a very BRIGHT light to examine to see if some component has been moved and is getting one of its connections pressed into another, creating a short. Be extremely sure that is not occurring.

    Secondly:

    You can see how FLOPPY that chassis is being in its upward and downward movement, if being slid back and is not supported by its two side rails.

    Get the set working normally with the chassis pulled out and then get a hold of the corner at the tuner coax fitting and the rear corner of the opposite of the PCB and lift the whole PCB upwards at the rear to see if the set goes into your crazy no video with retrace lines situation being shown .

    There could be a hairline crack / break in a copper foil path and with gravity holding the board bowed a bit, the foil edges are touching and all is working.

    When you get the board in the rails and the board starts straightening itself , with no bend, the foil paths separate and open circuit.

    That’s about all that I can imagine with out my being there hands on.


    73’s de Edd
     
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  5. Cannonball

    Cannonball

    191
    53
    May 6, 2017
    I don't know if this will help.

    Pull the circuit board in as far as you need to get it to work properly. Slowly slide the circuit board in until you lose the picture and get the retrace lines. Try flexing the pcb without moiving the pcb in or out.

    You may need to check the pcb underneath the flyback for cracks in the circuit trace. also the CRT ground wire.

    I hope this helps.
     
    srijib likes this.
  6. srijib

    srijib

    3
    1
    Sep 4, 2017
    Thanks all for your reply, I managed to figure out and fix the magical issue. It was the loss signal cable connecting the main PCB to the CRT pcb. I heard cracking sparking sound while sliding the PCB inside. The observed the PCB bottom while sliding and found sparks due to lose soldering join. So Fixed it now.

    Thanks again to all.
     
    [email protected] likes this.
  7. Cannonball

    Cannonball

    191
    53
    May 6, 2017
    I am glad to hear that you have fixed your tv. I knew you could do it.

    Have a good day! Cannonball
     
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