OK, the output measurements look fine. The others are not.
Since you say the amplifier does work, they can't be correct measurements so are you perhaps misunderstanding which terminals are base and emitter? For certain, the voltage across this diode type junction will be in the vicinity of 0.6V on a working transistor. Check the measurement on other, small transistors.
Since it does work, it's unlikely you have such basic transistor faults so don't be too concerned about this test now. What is now more likely is bad, broken or missing earthing of the signal, output and power connections. If you don't understand correct earthing methods, check out the articles at
ESP website
Since you say the amplifier does work, they can't be correct measurements so are you perhaps misunderstanding which terminals are base and emitter? For certain, the voltage across this diode type junction will be in the vicinity of 0.6V on a working transistor. Check the measurement on other, small transistors.
Since it does work, it's unlikely you have such basic transistor faults so don't be too concerned about this test now. What is now more likely is bad, broken or missing earthing of the signal, output and power connections. If you don't understand correct earthing methods, check out the articles at
ESP website
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OK, but we need to see the internal details like the circuit board top and bottom, wiring etc. Considering the build of these mixers, we may not be able to see much anyway in the usual complexity inside. I suspect you may have to carefully trace through the wiring and determine the earthing issues as you go.
Obviously, the way to proceed is by dividing the problem up, so start with disconnecting possible hum sources in circuits before the amplifiers so that you are only looking at the amplifier(s), for example. Get the schematic diagram and some experienced assistance or you will be blindly guessing and wasting a lot of time as you proceed further, if necessary.
As posted earlier, this is a topic for a new thread and should really be posted in the Live sound>PA systems forum. I can't guarantee how much interest from more experienced PA guys you will get here, as I'm not very experienced with this type of gear.
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