The AT9000 MK1 and AT9000 MK2 models require a power supply in order to function properly. Purchase this power supply as a replacement or a spare for the power supply that came with the unit with your original purchase of the AT9000.
AT9000 MK1 Power Supply: UM37402 11-4005-0667-8
AT9000 MK2 Power Supply: UM37555 11-4005-0171-1
*Please note that the AT9000 MK1 model is a discontinued model.