Before you buy a replacement motherboard try unplug power, press power button for 30 sec, then replace cmos battery with a new battery and clear cmos settings by motherboard jumper. there is a blue jumper and 6 pins next to cmos coin battery on mobo. The mobo has instructions printout which 2 pins are for clear cmos.  pin1-2 are clear cmos.  default jumper is on 3-4. move jumper to pin 1-2 for 10-15 sec then move back to 3-4. [IMAGE]  
Hello Dell community! I have a dell Optiplex 3070 micro that won't boot! The power button is blinking orange. It seems that the motherboard has stopped working. Who can help me with information on where I can purchase a new original or second hand motherboard?
Montheboard 3070 micro