In my case it was one of the two 150k 1206 packaged SMD resistors that had gone open circuit. This caused the E4406A to fail to start up. I had to remove the 150k resistors to measure them out of circuit. I replaced both of them even though one of them was still OK.
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A couple of the 1206 packaged 100k resistors had failed in the past. this caused an issue with the fan control. It caused the fan to stay at full speed. Very noisy!
