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Horizontal line across the screen on Samsung tv CS29K3NTBX

 
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Jujeet



Joined: 25 Mar 2007
Posts: 22

PostPosted: Sun Apr 01, 2007 2:38 pm    Post subject: Horizontal line across the screen on Samsung tv CS29K3NTBX Reply with quote

I am working on a Samsung TV using Chassis KS3A(P).Its having vertical problem.I have replace LA7845 but to no avail.
There is vertical sync at pin 7 and sawtooth drive at pin 5 of LA7845.
I have scope up the waveform at pin 2.It reads about 50Vp.p
Can anyone help?

This is how it looks like:
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cory
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PostPosted: Sun Apr 01, 2007 8:13 pm    Post subject: Reply with quote

not for sure but looks like might be bad yoke.
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minnie



Joined: 18 Aug 2005
Posts: 2877
Location: Hell

PostPosted: Sun Apr 01, 2007 11:13 pm    Post subject: Reply with quote

You have to make sure your getting your voltage to the IC. Don't forget about the pump up caps. They could be dry.
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tv.service



Joined: 30 Mar 2007
Posts: 19
Location: Sweden

PostPosted: Mon Apr 02, 2007 1:50 pm    Post subject: re Reply with quote

Have you checked that you have supply voltage at pin 6 (+16,5v)?
Pin 3 is supply voltage for output stage.
Pin 1 is ground. I think this one is -16,5v. Not sure but i think so.

/janne
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Jujeet



Joined: 25 Mar 2007
Posts: 22

PostPosted: Tue Apr 03, 2007 3:09 pm    Post subject: Vertical Problem Reply with quote

Thanks guys for the information regarding Samsung TV chassis KS3A(P).I have checked the presence of the two voltages - +16.5volt and -16.5volt. The pump up capacitor 100uf 50v is OK.I have scope up the output waveform at pin 2 of LA7845 it seems to be OK . View it below and plse comment.If the yoke is faulty how come the waveform is not affected?

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tv.service



Joined: 30 Mar 2007
Posts: 19
Location: Sweden

PostPosted: Wed Apr 04, 2007 6:03 am    Post subject: Reply with quote

Is the heater glowing in crt?
Do you have the video signal present at crt board?
Do you have outputs for about 150v on each cathod?
Do you have enough hv?
What happen if you turn up the screen?



/janne
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steviewonder
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PostPosted: Wed Apr 04, 2007 9:12 am    Post subject: samsung ksa 3 Reply with quote

hi there.you are barking up the wrong tree here!what you have here is a short on the horizontal scan coils.this is caused by corrosive glue,which eats away at the insulation on the windings.if you remove the yoke,you may be able to repair this.
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Jujeet



Joined: 25 Mar 2007
Posts: 22

PostPosted: Wed Apr 04, 2007 2:30 pm    Post subject: Vertical Problem Reply with quote

I have removed the yoke and checked for excessive glue.There is no excessive glue on the horizontal scan coil.The horizontal coil reads 1.5ohms and vertical coil reads 12.5 ohms.Is there anyway to check that the yoke is defective?If the horizontal scan is shorted the horizontal output transistor should be blowing up.You can view the image of the yoke coil below.I like see some comments on this from you guys there?
If its the vert scan coil why is waveform not affected?If its the line scan coil why did not the horizontal output transistor cooked up?


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user
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PostPosted: Wed Jul 20, 2011 6:30 am    Post subject: vertical problem Reply with quote

any finding on this? is this really yoke problem? pls share
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arun
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PostPosted: Mon Jan 02, 2017 3:51 am    Post subject: tips Reply with quote

i know the fault were it is remove yoke and at back side of yoke they have 2 half piece of magnetic coil remove and check it the coil is burn and you join it the problem is solve
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