Working in a student computer lab and have had several, 5 fail out of the blue.
These are T1600s, running Windows 7, single monitor. They will never boot at all, so no monitor and no reading a diagnostic. The power supply test button at the plug does stay green when pressed and held. The fans will run during that process, however nothing else. The error code numbers on the front cycle through different patterns and on all but 1, stops at 3.