Hi, guys! I' ve got an Alesis electronic drum when I put the headphones on to the phone entry, I can't hear the sound from the right ear side of the headphone. I've tried it with different headphones and it was still the same so the problem is not related to the headphones. Can you help me ?
Oh damn, man. I ran into the same problem when I owned an Alesis DM10 Studio. It's basically some kind of loose connection, but I never got around to fixing it. If you show it to someone skilled in electronics, they should be able to fix it cheaply. That is, of course, so long as it's not something hooked up to the board that has gotten spoilt. 

Let us know if you could get it sorted out. 
Strandberg Boden 8-String Ibanez RG2228
Fender HM Strat ESP Horizon-II Five-String Bass
Roland TD-30K Mesa Boogie Mark V:25
EVH5150III 50-Watt Yamaha Motif Rack XS
Access Virus TI Snow Polyend Perc Pro