Vintage Synth Repair

hi,

i am new on this group, someone tell me that i could find answer for
vintage synthe.

i have a vocoder vp330 from roland corporation, i think is the first
serie with digital button on the front panel. it doesn't work
when i turn it on , the power led is ok, but when i play there is no
sound on the output , i try line out, and phone output but no sound 
and no noise

does someone have an idea of this problem ?

thanks a lot for helping me