magjoseki

I just acquired a Sony MZ-R70 when my Panasonic MD (forgot the model #) broke. The MDs that I recorded and played with my Panasonic are not playing on the Sony. The display shows the discs turning, chapter numbers and time remaining etc., but NO SOUND. One MD does produce sound on Track 1 only. The other tracks, same problem. I tried these discs on my friend's Sony MD, same problem. Please help ! J.K.