Question Gpu flashes blue but computer won't turn on

[Fengstar1]

Hey guys I have a very old system that recently died. Whenever I try to boot it the video card blinks blue once and nothing else happens. At first I thought this was a dead gpu so I bought a new one, but same thing. Is the power supply fried?

 

[Lutfij]

Without informing us what you've got to work with, we're(the community) essentially flying blind here. Please include the specs to your build like so:
CPU:
Motherboard:
Ram:
SSD/HDD:
GPU:
PSU:
Chassis:
OS:
Monitor:
include the age of the PSU apart from it's make and model. If you got relpacement parts for the system, add them as well so we know what you've replaced/swapped out.

 

[Fengstar1]

Apologies. The system is very very old and is just used for browsing mainly but I'll try to list everything!

CPU: amd phenom II 955

Motherboard: asus m4a79xtd evo i believe

Ram: some ripjaws? really can't remember

SSD/HDD: I think a regular samsung hard drive

GPU: had a 5770, bought a rx 580 but both just blink blue and computer won't boot

PSU: corsair tx650w

Chassis: cm storm scout

OS: windows 7

Monitor: acer 24''

The entire system no joke is probably 10-12 years old. Been very reliable so never touched it.
If I need to replace the psu, what is a cheap and fitting one to buy for the rx 580? Thanks in advance.