Hi All, I need the ops/service manual for either a Sony BVH-500 or RCA TH-50A (which Sony made...they are the same unit, different name plate) portable 1" vtr (circa late '70's). I also need the same for a Concord B/W 1/2" R/R vtr #vtr-820 (early '70's). Please email me in addition to posting here. Thank you for your help, Rick.