Behringer Xenyx Qx1202usb Service Manual

| Symptom | Likely Cause | Service Manual Clue | |--------|--------------|----------------------| | One channel dead, others fine | Broken solder joint on the XLR or bad NJM2068 op-amp | Schematic shows signal path from pin 2 of XLR to IC7a | | All channels hum loudly | Broken ground connection at main power header | PCB layout shows main star ground near C102 | | USB playback works, no recording | Fried PCM2902 or cracked ferrite bead on USB data lines | USB section shows FB1/FB2 – easy to check with continuity | | Phantom power works on some mics, not others | Q1/Q2 switching transistors failed | Shows +48V going through 6.8k resistors and transistor switches |

If the computer does not recognize the mixer, try a different USB cable or port directly on the motherboard (avoid unpowered hubs). behringer xenyx qx1202usb service manual