I just purchased the behringer djx 700, and the channel 2,3,4 are all distorted when i play music. Even when i listen to it through headphones you can still hear the heavy distortion. What can i do to remove the distortion?

See if another audio source connected to the mixer produces the same results. Try with the same cable and then with another cable. The purpose of this procedure is to determine if it is the cable and/or the laptop. (Sound card problem???) or mixer.
Is it ALL audio or just specific audio from for instance, a music application? Does it cut out using iTunes?
The mixer may have a bad or oxidized input. Try a different input channel? Are you using headphones to listen? It may be the headphone amp? OR, if audio is produced via amped speakers, it may be the mixer output. Does the mixer have metering? Do the meters also cut out? Does the laptop do the same thing if plugging in headphones to the laptop directly (no mixer)?

Actually, you may be in luck. A burned cap means that it has done exactly what it's supposed to do. So...you might stick an identical one in there -- it's a 0.1 uF cap, and you can find these at Radio Shack (0.1 uF 50V) or online. They are cheap, so give it a shot.

Transformers rarely fail... you wasted money on that... Likely one of the rectifier diodes/module or filter caps has shorted. Continued use will burn out the transformer. It is humming because it is overloaded with failing components.

Does the distortion ALSO appear when you listen with headphones? If not, the problem may be downstream. The driver for the mute control line to the mute transistors may have a problem. Make sure the mute is off.

If you don't have the manual it is here:http://www.behringer.de/EN/downloads/pdf/DJX700_P0165_M_EN.pdf Have a look at page 4 under Monitor, mode switch and mix control. You might be having problems with them.

Have a look at page 4 of your manual under the Monitor section, mode switch. Manual is here:http://www.behringer.de/EN/downloads/pdf/DJX700_P0165_M_EN.pdf The mode switch may be faulty or the mix control may be faulty.

studiospares (in london) or radioshack in USA, unscrew and get busy with a soldering iron, its not too hard, only 4 cables.

Suspect a ground problem someplace in the system.

Make sure your system is plugged into exact same recepacle that anything else you connect to is plugged into.

Also make sure a spot light is not heating it.

This is a wild educated guess.

I repaired a Behringer guitar amp that had a DSP effects in it (BX1200 I believe).

The effects were on a seperate board and the board had its own 5 volt power supply. The filter capacitor for the 5 volt power on the board was UNDERSIZED and it had degraded causing the 5 volts to drop out of regulation, dipping to 4 volts. This caused the DSP effects to fail.

YOUR device MAY use the same DSP OR design.

Check the 5 volt power with an OSCILLOSCOPE to look for dips below the 5 volt operating point that occur at 120 HZ.

Behringer only gives schematics to their authorized service people.

I find I can usually trace stuff out as needed as the mixers are a very symetrical repeating circuitry.

Most components are readily available from other sources.