No audio from Panasonic dmr eh 60 deb?

I have a panasonic DMR-EH60 DEB RECORDER (had it for about 4 years) and this week I have lost the sound from the unit and just get a hissing. Have tried all connections and tried swapping scart leads but still the same. The digital box feeds through the recorder to the tv and I can get sound from this with the recorder on standby but as soon as it it switched on I lose the sound. Have you got any ideas.