yamaha ps-3 doesn't work

I'm Hemantha,

I recently received a yamaha ps-3 and there is a some problem. It doesn’t work .

I checked the circuit board according to the Service Manual, but I couldn't fix it.

Please anyone can help me to repair it?

I gave some negative pulses (about 1kHz frequency) to FO,Vo, IC3 pin 1,2,6,7,MO1,MO2 like this. At FO,VO point, Occurred loud sound. At IC3 pin 2,6 point, Occurred mid sound. At IC3 pin 1,7,MO1,MO2 point, Occurred too week sound. However, when I press any key doesn't occur any sound.

(I have some little knowledge about electronic. I haven't oscilloscope)

Thanks.

Hemantha.