Hi Brach,
The FBL is on the correct lug, I ended up removing the PCB and discovered solder has bridged a cap which I repaired. After reassembling the chassis, all the DC readings are spot on, and I’m now able to get some feedback when I install an input cable. However I still can’t get sound from an instrument; and when I unplug the speaker, I get a high pitched very audible buzzing from the chassis.