Why behringer speaker sound goes high and low model B215D

SOURCE: i have a proble with my speaker pig tail it keep

Loop cables through the handles at each end as people tripping over cables yank them sideways breaking them.

SOURCE: I have a B215D Behringer

This should be close to your schematic;

http://elektrotanya.com/behringer_b215a_power-amps_psu_sch.pdf/download.html

Scroll down to "Get Msnusl" link and download. Leaving it on should NOT have caused a failure, however, if it was running and the input was not being driven there may have been feedback going on that did damage. Only thing to do is take it for repair.

SOURCE: Eurolivee B215D - I press

What your amp is doing is going into protection mode. The Class D amplifier topology uses a Pulse width modulation scheme which allows the audio to be modulated onto a generated square wave or pulse train. This is then sent through the MOSFET Driver and then to the High Power MOSFETs that drive the load. The square wave with modulated audio is then filtered by a low pass filter and you are left with your audio. This is great because of the very high efficiency. The downside is that there are more links in the chain to fail. In your case it sounds like one or both of your power MOSFETs are bad and are causing the watchdog circuit to send a shutdown signal to the switching power supply, this is why it is turning off. It is a safety feature to prevent catastrophic failure of the board. (ie. burning the PCB to a crisp) A technician experienced in PCB level troubleshooting shoot be able to repair this for you. Let me know if you need anything good luck.

SOURCE: As soon as I turn

How do you know you are at 40 WATTS? This takes electronic test equipment to measure.
Tests to run. Observe the speaker cone with power off. Now turn it on... did it displace and stay there? If so you have a failure of the amplifier itself. Next, If you can place finger on the cone, move it gently in and out feeling for any roughness. If you feel roughness, the voice coil is fried and you be buying new speaker. A lot of the Ultra bass Behringer's use LM3886 power amp chips... sometimes in parallel, and a failure of one could cause this.

SOURCE: No sound out of Behringer BXL3000 speaker

Suspected Faulty PC board Dead Capacitor Or Mod Pot I would suggest returning it for an exchange the problem is your speaker will work on a regular stereo because a stereo powers the sound internally causing the magnets in the speaker to vibrate Headphone jacks are designed to pick up off a seperate circuit board with a different connection to the main board hence the no sound from the speaker.