Can you run a powered mixer without a speaker load

i suggest you contact Behringer Customer Service for advixce. Without the setup in front of me, it's hard to figure out the wire routeing, switch positions, ect. that may be leading to this problem. As they would be the people most familiar with the gear, they'sd be the people to ask. http://www.music-group.com/support/behringer/askquestion

Without knowing what make and model of the gear you're looking to connect, I can't give you a definitive answer. However, in general, if you have a powered PA mixer, meaning it has both a mixer section and a power amp section in a single box, the main speaker outputs will be on the rear panel of the box and marked as such. There will also be a jack for monitors, but some mixers have an amp for monitors, some just have an output for the monitor mix, but not an amp for them, and on some you can switch the main outputs to feed either a Left and a Right speaker, or a front mono speaker and a montior speaker. Instruments will go into the individual channel inputs.

First it is certain that you would not want to plug both outputs of the stereo power amp into one speaker combining both channels into the same speaker. (see image from manual below - also link to manual)

Next I would be very concerned about only using the one side of the main amp out as it could cause an unbalanced load, or you could be driving the load into dead air connection and any of these conditions are destined to cause premature failure of the power amp.

Taking a quick scan of the manual for this unit, it appears what is pretty common to most powered mixers, hook up two matched speakers/loads to each chanel of the output.

Your best bet is to shed those monster cabs, there really is no need for them especially with this sized powered mixer, and get yourself a nice pair of full range cabs like EV1202;s, EV SX300's, or some nice 2 or 3 way 15" JBL's/

Just my opinon.

Link to Yamaha EMX 312 Owner's Manual:

Yamaha EMX Series Owners Manual

First check your speaker's impedance and connection configuration, let me know more.

Does the left meter do the same thing? If the meter matches the right one, I would suspect the volume potentiometer on the powered speaker. Try exercising the volume knob. There might be some oxidizing on the potentiometer.

Essentially if the fuse goes, the unit is rendered useless until it is repaired. Replacing the fuse without repairing would likely cause further damage in the unit. Fuses blow for a reason that is usually a failure in the unit. Failures don't fix themselves. The ability to replace the fuse is therefore a moot point. To keep your unit safe ALWAYS power all interconnected equipment from the SAME power receptacle or conditioning module. This means running extension cords to powered speakers if that is what you have to get power the mixer. Powering mixers at one end of a room from a receptacle and the amps or speakers from a recpetacle on a stage at the other end will likely damage you equipment when a ground fault occurs or ground bounce in the building wiring ruptures the sensitive input/output circuits of your equipment.

If you run the speakers FROM the main you should have BOTH the effects and the EQ invilved with your signal.

ALL the speakers will either have to be POWERED or have external amplifiers. The mixer has NO power amps capable of driving speakers. When connecting, make sure that the mixer is powered by the same receptacle as the speakers or amps. Used balanced line for interconnection.

UPS will not help this. Make sure you are using GOOD quality balanced cables, preferably XLR to connect to powered speakers. Make sure ALL (read that "ALL" closely) of your equipment is powered from the SAME receptacle or power module... this means run power to your mixer or speakers alongside your audio lines or snake between the units. This includes ANY other devices tied into your mixer with the exception of truly ground lifted DI's.

Good way to pop speakers is to run them on stage power and mixer from plug at the rear of a room... The common mode ground noise will exceed the common mode capability of the audio inputs and fry them.

Supposedly one pushes down the FBQ button and the LED's in the EQ handles light for those with feedback and you adjust those till the lights go out.

More importantly I want to caution you to NEVER run this unit without a speaker load. There is an arc over condition in the rear-most power amp that kills the unit. This can happen even with everything connected. It causes major damage. At the slightest indication of flakey behavior, power down and take in for service.