change new LCD still touch screen not working

hey,

i bought mobile from ebay touch is not working, i thought its the lcd , i install new lcd but the result is same,

so i used the old lcd in other mobile surprise the touch is working fine other mobile but not working in my first mobile,

what would be the reasone of touch is not working

what i can do to repaire the logic board or what ?

shall i change the touch digitizer from logic board or need to do some test ?

hope you reply soon

salman