Resolution of the MSR-8000, turns out one of the two SMA connectors and cables that bring audio into the 1A1A3 card was internally shorted. It's the connector for the high-level carbon microphone feed that goes to 1U(B) directly. That pulled the audio down at the junction that feeds pin 3 of U1(B)  but because the 1 kHz signal for CW is injected past U1 that's why CW was not affected.  Have seen SMA connection fail before on other radios. 

Sorry, but still no love for Mackay products.

Ray F/KA3EKH