technics SA 5070
older technics receiver. speaker output is not working. i hooked it up to powered sub using the line level outputs from the tape loop. fm tuner section works. picks up signal fine. sub has built in amp. gain and crossover settings. i adjusted gain and bass output is fine. i did not try the headphone jack to see if that works. the IC is stk 043 105. i see many stk 043 chips online for $15. says they are 20W approx. think a chip swap might fix it?