if the computer fails the POST, the computer emits a series of LED codes during the start-up. freeze and 2-7 blink suggest possible memory failure. Try remove all ram, put only one back in DMM1, take POST.  test each ram this way individually. Blinking Amber:Boot Failure - The computer is receiving electrical power, and power supplied by the power supply is normal. A device might be malfunctioning or incorrectly installed. See the table below for Amber Blinking Pattern diagnostics suggestion and possible failures.
Yesterday my G5 5090 Desktop froze and wouldn't respond to anything. My USB keyboard, mouse and headphones lost power. The display was still active, just stuck on the last frame displayed before the computer froze. I shut down the computer by holding the power button, and when I tried to start it again, I heard it turn on, but it didn't do anything. The front blue LED was not on and there was no display. The power light was an amber colour, and it was blinking as follows: 7 times, followed by a pause, then 2 times and a pause, before repeating. It may have been the 2 first, then a 7, I do not know which came first. I've looked in the Dell manuals since but I couldn't find anything corresponding to a 7-2 or 2-7 amber blinking code. My main question is, what does this actually mean? Further details are below: When I would shut down the computer like before, it would restart itself a few seconds later to the same blinking as before,, so I turned off the switch for the wall socket it was plugged into. I decided to turn the switch back, and funnily enough, the computer started and booted into Windows. The whole process of freezing, blinking, flipping the socket switch and starting up again happened 3 times between then and today, where now even after killing the power I can't escape the blinking lights. TLDR: What does a blinking power LED following a pattern of 7 amber blinks, 2 amber blinks (or 2 and 7 as I have no way of knowing which came first) mean? Thanks
G5090 blinking power light