[SOLVED] PC not starting after crash

May 22, 2019

Hopefully someone can help me out with this because I'm stuck.
My desktop won't start anymore after it crashed while I was playing a game.
The story is as follows: A few months back my pc crashed while I was gaming. The screen went noisy and I heard a loud static noise through my headphones for a second or so and then the screen went black. The pc did restart, but only after a few attempts. After that, the problem didn't occur anymore until now. Last week I had the exact same problem, except it didn't solve itself again. Every time I try to start now, the screen just stays black.

CPU: AMD Ryzen 5 1400
RAM: 2x 8GB Crucial Ballistix Sport LT BLS2C8G4D240FSB
GPU: Radeon HD 7970
Motherboard: Asus Prime A320M-K
storage: 250GB ssd (boot) + 500gb hdd (storage)

-Motherboard is powered when trying to start up, leds and fans turn on, also te leds of the mouse and keyboard are powered.
-Tried a different monitor. no result
-I have monitored the temperature of the GPU while gaming. It can get to about 70 degC while gaming for a prolonged period of time. CPU temperature always stays below 50 degC
-Of course I tried to power cycle fully. no result
-Tried disconnecting everything and then connecting everything before restarting again. no result.
-Tried clearing the bios memory by reseating the CMOS battery. no result
-Manually tested all the outputs of the PSU. They are within ATX tolerances, so the PSU is not the cause.
-Tried to remove the graphics card an then run with to the integrated graphics. This had no result (can I conclude from this that the graphics card is not the issue?), but when I installed the graphics card again, weirdly enought, the pc did actually start. It was even able to boot windows. However, as soon as I had logged in, the pc crashed again (same crash). After that no signs of life anymore.
-Tried disconnecting the storage devices and starting without. no results.
-Tried booting with only one stick of RAM, tried both sticks. no results.

I hope that this is enough information for someone to make an educated guess about the cause of the problem. What should be my next step for finding out which part is defective?
May 22, 2019
Thanks for replying.
I haven't tried a different PSU yet, since I don't have one available. I'm not sure about the exact age of the one I have now, but it must be at least five years old. I tested it by forcing it on and measuring all its outputs with a multimeter. As I mentioned, the outputs are all within tolerances.
May 22, 2019
Update: I found an old graphics card and tried to start with that one and the pc booted just fine. That means the graphics card is broken. The reason that the integrated graphics didn't work is simply because the Ryzen 5 doesn't have integrated graphics.