32 toshiba tv problem

    helpppp, my toshiba tv model 32a33,  the demo starts up sometimes right away and then sometimes after 20-30 min.  and i try to stop it and sometimes it will but mostly it won't. new batteries in the remote no help, desolder the tv/video button in front of panel no help, and also the menu button no help, called tv  techs  never had that problem but bring it in will try something, ya.any one can help thanks..berry