Your Tevion TV has a cold-fault - it only works correctly when it's warmed up. May be one of several components but is quite likely to be power supply related.
It may be possible to diagnose it without test equipment and circuit diagrams but you'll need to open the case.
Apply gentle heat from a hairdryer onto the component parts and see how the picture is affected - then let it cool down and try again. Gradually focus on the specific bit that brings the picture up.
Do not expect a quick fix.
Good luck...
December 2014
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