Reply to Very low volume. Technic 1210MK3D

Hi i just picked up a second hand pair of 1210MK3D they came in almost new condition, everything is working fine with my serato box except, one of my turntables has almost completely dropped the sound from the left channel (you can hear it, it's just very low in volume). Now i have cleaned the tone arm contacts, re-soldered the rca cables and soldered new cable also, but the problem still persists. I'm now believeing something wrong with the tone arm itself? Anybody ever had this problem? What did you do to fix it? Any help would be greatly appreciated.