I've got a 27" iMac i7 - EMC2429. When the machine is powered on, the screen has an ombré effect going on from bright at...

Hi Ben, sometimes cleaning isn’t enough. When liquid hits the interior, it can also short out circuitry. Given that you’ve tried everything else. I’d bet the logic board needs micro-soldering or replacing. Micro-soldering takes longer (you have to send it out), but is cheaper.