I also have one summing amp and one oscillator card, but only three edge connectors.
I have a copy of the mixer manual that the cards came from.
Manual says that the cards want to see +33 DC.
From the schematic, I was able to determine the power connections and the balanced in, the rest is Greek to me.
So.....powered up a preamp and sent signal to the input using an unbalanced source and a DI.
Determined that there are two output options.
Pin 4 and the wiper of the Davin 5k pot (pin8) both have clean signal.
I am guessing that the pictures of the API meters I posted are from the original chassis.
Why I have two is a mystery, as there is only one per mixer.
Nathan
Don't know why, but I don't see the expected option to reply to your PM.
Last bit has nothing to do with selling Bruce's' gear.
A bunch of us have got together to demo and rebuild Bruce's' garage.
At almost 68, I am having a bit of a tough time keeping up with the young bucks. :-\
cheers
Roly