Picture Cycle On Sony type BE3D

hello,

I've this problem with a TV KV-29X1B

After start on sound is ok, but the picture appear only after 10min... and then blink...

If i change the channel, the picture jump(goes 10cm up and after that return ok), there is too a little sound from the HT circuit at this moment...

What should i check?

Thanks!

Rifo