Monitor hum with no audio output

Jonbonspumoni

Estimable
Jul 8, 2015
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4,510
I have a set of Mackie CR4 MM Monitors, one passive, one powered. When I plug in the powered and turn on the main I only get a loud hum at about 120 Hz and it won't put out any other audio. The passive speaker works just fine when connected to another power source. Any idea what might be causing the issue with the powered monitor and how it might be fixed? Also, the powered speaker has a volume knob on the front which doesn't seem to affect the volume of the hum.
Thanks!
 
It sounds like the amp is bad. Hope they are under warranty as replacing the amp might be pricey.
If you remove the amp you can visually check it for burned components but without service skills and parts list it might not be something you can tackle. To have a technician do it would be more than the price of the pair of speakers. Check with Mackie.