Obviously if they've tied µPD1771C's Vcc to GND they had to make its GND pin negative WRT that. Why and how they went about that though...? Let's hope D1771 tolerates more than 5V supply. Is it warm to the touch?
Attached a portion of schematic with a different revision of the D1771 that should be helpful, pinouts seem to match.
Check what's going on on pins 6 (/PORest?), 9 (CLK IN), 15 (Unknown / Pull-up resistor?), 10 (Unknown), 18-21 (Data bus).
Have you tested the speaker itself is working?