TV SIEMENS FC872 -NO SOUND EN 1-2-3-4 PROGRAMS-

[escanlar]

It is an old but good SIEMENS TV (MOD FC 872)that has no sound in the 1,2,3 and for program positions. I think it may be a code problem but I have no any manual or  squematic diagram, so I need help to save the problem. Many thanks
Escanlar