CiT Pemtium 500u PSU seems to have died?

Hello,

So I was randomly using one of my desktop PCs earlier today. I had just started the PC and was browsing on Google Chrome. All of a sudden, I started hearing a hissing noise coming from the back of the PC. Motherboard instantly switched off.

Upon trying to power it up, there was no response. I unplugged the power cable and plugged it back in. Soon after plugging the cable back in, the hissing noise came back and the LEDs on the motherboard and front case fan flickered before turning back off again. The noise stopped and trying to power it on via the front case power button gave no response. It becomes lifeless after the initial hissing noise/LED flashes.

I thought perhaps the power cable may have gone bad, so I got out a spare one I know works fine. So I tried the same thing again (simply plugging the cable in), this time paying close attention to the back of the PSU. I could see blue/orange flashes coming from inside the PSU along with the hissing noises. After this, I unplugged the power cable and didn't bother repeating the tests.

I'm planning to buy another PSU (I've been meaning to do it anyway). However, I am a little curious as to what's wrong with this PSU and I'm just wondering if it's an easy fix or not (just some bad caps or something else that's not overly complex).

I've opened up the PSU and carefully had a look around. I don't see any burn marks and the caps don't seem to be that bad-looking.

Here's some pics of the PSU (not the best quality):

I can take more images of the board if needed.

I did notice one thing after looking more around the board. It seems a resistor marked R50 was meant to be there, but has mostly vanished? See the below image:

As you can see in the above image, it looks like most of the R50 resistor has simply blown off/vanished. Could this be the problem? It's near a 16-pin IC marked "EST7502C".

Appreciate any help on this. I know it's not worth repairing, but I am still curious to see if it's actually a fixable fault.