If an op-amp goes faulty, it invariably has full DC on its outputs, either +15v or -15v.
The circuit diagram you posted appears to have incorrect pin designations on the op-amps, however.
It shows the outputs to be pins 2 and 8 which is not correct, they should be pins 1 and 7, like most every other 8-pin dual op amps in existence.
https://www.mouser.com/datasheet/2/294/NJM4560_E-365030.pdfI actually think, from the diagram, that the op-amps are probably OK, since a blown dual op-amp usually has both outputs on DC.
This design (stupidly IMHO) uses 2 dual op-amps where each op-amp has one half powering the left side, and the other powering the right, so should this op-amp fail both left and right are likely to dissapear.
Anyway, forget the pin numbering issue for now, the safest thing to do is to find the 2 capacitors on the op-amps outputs, C715 and C716, and probe there to see if the opamp has a DC output, and/or this is where the signal disappears.
I suspect C716 is faulty.