Lanzar Opti 2000D no audio.

Good day threaders, I have a Lanzar Opti 2000D the amp was sent to me from another repair bench. The amp powers up well no device are overheating but I can't get any audio. I've replaced the audio driver board twice with a known working one.
I've only checked the main source voltages so far, like rail Voltages and op amp voltages and they are in their respective threshold 80+/- and 15+/-.
I've heard the previous tech person had already replace the 13600D ic and all the TL072's in the frontend pre-stages.
I've checked all resistors and diodes and all seem ok (in and around tolerance). I've also checked for open solder joints for top layer to bottom layer on the PCB. Before I start replacing components is there any known culprits or failures these amps are associated with?