Audio Systems: Sound System in our church, voltage regulators, consule

Question
We have a 24 slide 4bus Mackie mixing consule. When we move the slides we have no volume control. When we move the 4bus slides we have no volume control. If we just move the gain of each channel we have volume control, but nothing on the slides. If we move the master we have sound level control. Can anybody tell us what's happened? ..or how to fix it. Thanks,
Larry

Answer
I'm on the run right now and don't have time to dig but my first reaction is you have lost voltage to the vco circuits on the masters.

Check the voltage regulators and dc lines feeding that section of the board.

I will dig deeper later but I need the model number.  Can't help without the model number.....

Thanks.