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Sanyo TV, Colour problems, HELP Please

 
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Mezza



Joined: 02 Jul 2007
Posts: 5
Location: dudley

PostPosted: Mon Jul 02, 2007 3:26 am    Post subject: Sanyo TV, Colour problems, HELP Please Reply with quote

I have an old sanyo widescreen tv.
model ce28wn4-b
chassis series eb6-a28.

the problem is the colour is all wrong, its like one of the R,G,B signals as gone and leaves the screen looking dull with bright red colours.

Any help would be much appreiciated.

Thanks Mezza Smile
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minnie



Joined: 18 Aug 2005
Posts: 2877
Location: Hell

PostPosted: Mon Jul 02, 2007 10:59 pm    Post subject: Reply with quote

How old?
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Mezza



Joined: 02 Jul 2007
Posts: 5
Location: dudley

PostPosted: Tue Jul 03, 2007 1:16 am    Post subject: Reply with quote

minnie wrote:
How old?


i'm not sure of the age, must be about ten years old + or -.

thanks
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torbjorn



Joined: 07 Jun 2007
Posts: 370
Location: Sweden

PostPosted: Tue Jul 03, 2007 12:31 pm    Post subject: Reply with quote

The Sanyo EB6 chassis was in production around 2000-2001, so that set should be about 6 years old.

I have had exactly this problem on a such set, and all that was needed to fix it was just to adjust the VG2 (screen) control.
Anyway, it would be a good idea to check that no resistor on the cold end of the screen voltage divider (R450, R453 etc) has changed value or gone open circuit.
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Mezza



Joined: 02 Jul 2007
Posts: 5
Location: dudley

PostPosted: Wed Jul 04, 2007 2:20 pm    Post subject: Reply with quote

thanks for the replies.

i have done what you said and all is ok with the resistors.
i did a voltage check on ic201(tb1252bn) at pins 16,17,18 witch are the r,g,b inputs and they read 1.4v each, the outputs at pins 20,21,22 are 2 of them read 2.8v and 1 reads at 1.4v. could that lead to a fault in the ic.

thanks mezza
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torbjorn



Joined: 07 Jun 2007
Posts: 370
Location: Sweden

PostPosted: Mon Jul 16, 2007 10:48 am    Post subject: Reply with quote

Well, as this set has automatic cut-off adjustment, the differing voltages could as well be due to a problem in the video output stages or the CRT itself.

Check with oscilloscope if the voltages at pins 20, 21, 22 vary when you turn the screen control back and forth, also check what happens with the voltages at the CRT cathodes. If you suspect the CRT, try breaking up the path to the cathode of the suspect color and another cathode (perhaps there is some series resistor that can be desoldered) and cross-connect them, then check if the faulty voltage stays with the cathode or with the output stage.
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