Since many of those measurements you're getting on the NE602AN mixer IC are indeed abnormal (and seemingly impossible unless internal or external components are damaged), I think next I'd try removing the NE602AN mixer, then take voltage measurements at each pin of the exposed socket. If you can post those measurements here maybe we can help troubleshoot.
Do you have a new NE602AN to try?
---In CHINA_QRP@..., <va7jbe@...> wrote :
I've observed this behavior while using both the microphone and shorting pins 5 and 8 of the connector without the microphone attached.