sandun chathurange sounds like you might be doing to much at once. This “change the chanels backlights goes dim and comes back on” is not a T-con board issue. That is a backlight issue. You did not tell us if you have sound. Also let us know how you checked this “No images, backlight is ok.” It’s a Samsung so you would only have to disconnect the wire from the power board to the main board. Your backlight should come on. If it does not it’s your power board that is failing. This “when disconnect the power to Tcon card some horizontal line pop ups and go” is not something you should be doing since it really will not show anything and might be more confusing. From what you have done thus far, it sounds more like a main board issue than anything else. Go ahead and measure the voltages on the power board connector going to the main board. Let us know what those voltages are, so we can determine if your main board sends the appropriate signals. Of course, a failed panel is always an option but unlikely. Check everything else first.