Check the inputs. If you can find the signal that's supposed to be coming out of it at either input pin, then there's a good chance the opamp has gone bad.
That said, I think the actual output amps are the THS3095s over the large exposed pad areas. Start from the front panel and test moving back. Also worth testing resistance of the inputs and outputs while powered down, if there's a short on anything, it's immediately suspect. If you can narrow it down, you can also try removing the IC with hot air and testing again without it in place - if the behavior changes/comes good (not at the output, but at the previous stage) then you probably pulled the bad one. If you remove the THS3095 (if it's the output amp) and the LMH6702 still has a bad output, then the bad one is probably still in circuit. There is a chance the THS3095 is gone bad and it's pulling up the output of the LMH6702, for example, so before you go buy a $10 opamp, it's worth checking.