regi

I bought a Sony MDS-JE320 minidisc player off ebay. it seemed to play my discs, but produced no sound. i took it to an authorized repair shop and now it plays at SP speed, but discs recorded at LP2 are not playing. I can see the TOC. the time count shows as the disc "plays", but there is no level read out and no sound. At SP speed, no problem. At LP2 speed, no sound. is there a setting i'm not aware of? the manual says nothing about SP or LP2 speeds. thanks!