Dell Optiflex 755 Flashing Amber/Orange Light

The Dell manual  HERE <ADMIN NOTE: Broken link has been removed from this post by Dell> is vague on the problem.

Here is what is says for a blinking amber power light.

If the power light is blinking amber, the computer is receiving electrical power, but an internal power problem might exist.

• Ensure that the voltage selection switch is set to match the AC power at your location, if applicable.
• Ensure that the processor power cable is securely connected to the system board (see the "System Board Components" section for your computer).

In many of the home/consumer models a blinking amber power light, in most cases, is a defective power supply.     Do you have a known good power supply you can try in one that has the blinking amber power light problem?  That would at least tell you if it's bad or eliminate the power supply as the problem.

Replace the front fan assembly PCB-P8482 or HU389 or P9847 or several others