@beezer4 Found my MCI 6xx manual and I have a headache following through the "logic" design for that portion of the MCI circuitry! lol
A real world test. Patch something (external oscillator, whatever but NOT the desk's internal oscillator) into a line input, bring up the fader so you have signal on the 2 Mix meters and can hear it in the CR monitors.
Be sure the desk oscillator is switched off. Select "Slate/Oscillator" to 2 Mix. Press the Slate switch. Monitors should mute, but what happens on the 2 Mix meters?
Turn on the oscillator. What happens on the 2 mix?
Next, deselect the "slate/oscillator" from 2 Mix and select "TKS" (tracks) and then turn on the oscillator. What happens? And what happens when you press Slate?
I used to know this.....<g>
Bri