Agree with Ehlerz. This is what you find in BS3 service manual regarding "EXTRA BLANKINGS Sub Menu":
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EXTRA BLANKING
It is possible to control the blanking time if for instance a Set-top box connected is
slow to synchronize to a satellite channel.
The startup of the picture is delayed (blanked) according to the setting belonging
to the chosen input socket.
AV1-6 can be changed from 0-15 seconds in steps of 0.1 second.
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Stefan