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Hello,
Thanks for the comments and suggestions. The drawing will be updated shortly with the clarifications suggested here in.
@Ferix
Going from a blue screen to black means something has been detected and the video decoder is no longer in free run mode.
Are you using the reduced amplitude TTL CSYNC signal or the CVBS(Composite) video connected to pin 20 of the SCART lead?
What is the voltage at pin 16 of the SCART lead when plugged in, it should be 1-3V DC?
What is the voltage at pin 8 of the SCART lead, when plugged in, it should be 9.5-12V?
If you disconnect the CSYNC signal, do you go back to a black screen?
I'm wondering if your TV is using the SCART fast blanking feature with Alpha blending. This is a mode where it blends the CVBS signal with the RGB. As you are feeding a TTL CSYNC pulse, it is quite rightly getting confused as the signal has no front/back porch to detect so black level and peak white are hard to detect. Just a theory at the moment.
Ian
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