Hi All
I routed out a EMX 3000 Yamaha Powered mixer recently expecting it to be OK however, when i connect it to speakers and I turned it on there a buzz from the speakers. All the faders were down including all the masters but still the same.
I disconnected the mixer board from the power amp section switched back on and the buzz disappeared.
The mixer works completely as it should i.e. faders, tone controls, DSP, and the volume change doesn,t alter the volume of the buzz it remains the same.
At one attempt switching it on the buzz was gone and the output was perfect but next time it was back and hasn’t worked properly since. The buzz is back.
Is there an experienced guy out there who might have an idea what it is.
Thanks
Ron
I routed out a EMX 3000 Yamaha Powered mixer recently expecting it to be OK however, when i connect it to speakers and I turned it on there a buzz from the speakers. All the faders were down including all the masters but still the same.
I disconnected the mixer board from the power amp section switched back on and the buzz disappeared.
The mixer works completely as it should i.e. faders, tone controls, DSP, and the volume change doesn,t alter the volume of the buzz it remains the same.
At one attempt switching it on the buzz was gone and the output was perfect but next time it was back and hasn’t worked properly since. The buzz is back.
Is there an experienced guy out there who might have an idea what it is.
Thanks
Ron
it could be anything that causes buzzes in mixers. If the noise goes away when the mixer is disconnected, then we can suspect the mixer portion or the power supplies.
You also report the noise goes away on its own sometimes. That just screams loose connection at me. A ground to some portion of the mixer could be loose or corroded. if it only went away ONCE, that could be a steady hum problem but the one time you had a issue with your setup that hid it.
So with it all connected, try pressing on each board and any internal board to board connections or ribbons or similar. Use a wooden chopstick or similar to probe the boards. Does touching ANYTHING in ther affect the noise?
With the machine closed up, ball up your fist and whack teh end of it. Does it react at all? It should not react.
Determine if the hum is 60Hz or 120Hz. They are the same note but one octave apart. 50Hz and 100Hz in some parts of the world. 120Hz is from power supply ripple, which could mean failing filter caps or connections thereto, or grounding problems involving power supply. Scope the 15v rails, are they clean? Are they both about the same voltage? I don't care if they are 15v or 15.3v or 14.7v, whatever. What I do want is both polarity supplies to be at about the same voltage as each other.
60Hz hum is usually from grounding issues, or radiated EM fields picked up.
Further tests:
plug a clean signal into the power amp input jack on the unit, does that signal emerge hum free?
Use the main out (not speaker out) or master out or SUM out, something with the main mix output at line level, and connect it to some other amp and speakers to see if the mixer signal itself has hum on it.
That ought to be something to start with.
You also report the noise goes away on its own sometimes. That just screams loose connection at me. A ground to some portion of the mixer could be loose or corroded. if it only went away ONCE, that could be a steady hum problem but the one time you had a issue with your setup that hid it.
So with it all connected, try pressing on each board and any internal board to board connections or ribbons or similar. Use a wooden chopstick or similar to probe the boards. Does touching ANYTHING in ther affect the noise?
With the machine closed up, ball up your fist and whack teh end of it. Does it react at all? It should not react.
Determine if the hum is 60Hz or 120Hz. They are the same note but one octave apart. 50Hz and 100Hz in some parts of the world. 120Hz is from power supply ripple, which could mean failing filter caps or connections thereto, or grounding problems involving power supply. Scope the 15v rails, are they clean? Are they both about the same voltage? I don't care if they are 15v or 15.3v or 14.7v, whatever. What I do want is both polarity supplies to be at about the same voltage as each other.
60Hz hum is usually from grounding issues, or radiated EM fields picked up.
Further tests:
plug a clean signal into the power amp input jack on the unit, does that signal emerge hum free?
Use the main out (not speaker out) or master out or SUM out, something with the main mix output at line level, and connect it to some other amp and speakers to see if the mixer signal itself has hum on it.
That ought to be something to start with.
high frequency buzz would have me testing the low voltage regulator section for a fault or open ground.
you did indeed say that the "buzz" went away when you disconnected the mixer from the power amp? (where you doing this via the insert jacks or where you removing harness connectors internally?)
you did indeed say that the "buzz" went away when you disconnected the mixer from the power amp? (where you doing this via the insert jacks or where you removing harness connectors internally?)
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