Your iMac 27 "At the end of 2009 refuses to turn on, or does the screen light intensify without you touching it? Or you sometimes even hear strange hums coming from your iMac ... This is probably linked to power the device! If your iMac has a power problem, it is better to solve it now. This is the reason why we are offering this 27 "iMac power card at the end of 2009! Once the power board is changed, you won't have any worries.