Expert: Cleggsan - 8/24/2010

Question
Follow Up... the model of our Board is SR24.4.VLZ Pro.(2004 model)

Would this mean we could rule out the amplifiers?

Answer
Previous correspondence:
Questioner:     Larry
Category:    Audio Systems
Private:    No     View Published Answer

Subject:    Sound System in our church
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.
============================

I think you can rule out the amps but to  check you should connect a known good amp or headphones or something to the output of the board on the same connector that is feeding to an amp and verify that it gives the same result as before.

Mackie has good customer service - have you spoken with them?

Do you have a technical person who knows how to troubleshoot and do some basic testing?  If you to to page 6/8 at this pdf

http://www.mackie.com/pdf/sr24vlzpro_ss.pdf

it has a block diagram where you can easily find the audio path for the audio path you are testing and clip on a signal tracer or something to pickup  the audio and test to see if you have audio and if the gain controls are working for it.  That way you can isolate just where the problem is occurring.  

And, finally, are you sure someone has not altered the channel configurations such that the channel you are missing has not been reassigned? or something like that?

Happy sluething...... Hope you get it going.