AMC CVT 3030 preamp problem

Muting circuit 🙂
I have never tried anything other than the J105, I cannot answer you, on the other hand that both are dead, it is more than surprising, you are sure that it is not the protection circuit in him who are you having trouble with ?

you have all the voltages on the diagrams, you can look at the side of the protection circuit and check if you have the right values and test:
2n2907 Q317
2n2222 Q318
1000uF/16v C325
zd 302
But start by checking the voltages against the diagram