My name is ***** ***** I will be assisting you today. Please favorite or bookmark this page press CTRL+D, so you can return here if we get disconnected. Can you be a little more specific about what you are seeing? Also try to get a picture of it and upload it here by using the paperclip icon in the chat window.
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Sometimes there is more than one yellow circle in the sky or on a white background. the blemish can vary in size. I assume it is a consequence of faulty tuning.
The yellow marks appear wherever the screen shows white or pale blue. It is often a large ring at the top centre the screen. I have also noticed mauve blemishes in pairs like lungs.
My desktop is not connected to the tv. I would need a small Lenovo adaptor lead and don't want to expose the contents of my pc to scrutiny by LG. I suppose I could take a photo, but that would take a few days.
I think the appearance of yellow on white or pale blue backgrounds shows it doesn't occur in just one place. It appears in areas at the bottom of the screen in squares and diagonals where there are whitish edges.
I would try retuning the set if I knew how. I assume I would have to reinstall it. I'll bear in mind your recommendation that I have the set serviced under warranty. I became aware of the yellow blemish when I played a black and white dvd.