surf

Am new to MD world. Have recorded about 1,200 hrs of music on Walkman N420D via Sonic Stage 4.0 w/o any major probs. Just bought used Sony JE320 deck for home use. It came w/ a homemade 74 min disk that plays fine. My 80 min disks appear to be playing (TOC, song length, etc. correct, but no level or sound present. 74min disk plays on Wakman. Downloaded manual of no use. Any ideas about what's wrong? (I don't understand the formats used if that's what's wrong) Any help greatly appreciated because I can't use my deck w/ my current library. Thanks.