Solved No signal after changing PSU

Welcome to PCHF Akabane,

Akabane said:

RAM: 8gb ddr3

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Is this two Xs 4GB sticks.

Akabane said:

Mobo: MSI (Don't know exact type... )

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We need to know this, it should be stamped on the motherboard somewhere.

What are the brand and model name or number details of both the old and the new PSU.

Is the MB at the link here the same as yours.

Akabane said:

the new PSU I got was Zalman ZM600-GSII 600W and the old one is 300W (Can't find the name)

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If the 300W PSU does not have an information sticker on it then it is junk and should be tossed in the trash having cut the power cord off first to prevent reuse.

The video card that you have requires 300W of clean and stable power and a minimum of 22 amps on the +12V rail, any PSU that does not have this written on an ID label will not be able to produce what is required, you will not only damage your video card (if not done already) but could potentially wipe out all of your hardware if the PSU goes pop.

Zalman are not brilliant but they are far better than any unknown brand.

Will come back to the MB.

Akabane said:

I had no issues for 2 years with that PSU. For some reason it just won't boot when I tried to switch the PSU.

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Couple of questions if I may;

Why did you change the PSU in the first place.

From where did you obtain the Zalman ZM600-GSII 600W.

phillpower2 said:

Why did you change the PSU in the first place.

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Akabane said:

the fan wasn't spinning sometimes. (But it still worked)

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phillpower2 said:

From where did you obtain the Zalman ZM600-GSII 600W.

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Akabane said:

And I got it from one of the biggest shops in my country.

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Sorry Akabane but this makes no sense, you had a faulty PSU so you replaced it with a new one then took out the new one and put the original faulty PSU back in, can I ask why.

Well sorry to say but it looks like the Zalman PSU may have been faulty and caused damage to your hardware, your video card is looking like a casualty at the very least
If it does prove to be likely that the new PSU was bad and you still had the Zalman PSU in your possession you could have taken this up with the store from where you purchased it.

Apart from the above, before continuing with troubleshooting you have to ask yourself is it worth it when you know that the present PSU is faulty, at the moment you may be looking at a bad video card but could end up with everything being ruined, up to you, let us know and we can suggest what you check but we accept no responsibility for any further damage.

Just so you know, the replacement Zalman PSU was actually made by a company called Hui Cheng Electronic Technology, had no minimum efficiency rating or any warranty period stated, what you call a ticking bomb

Honest answer is that you could end up paying someone more to look at the computer than it would cost for the new PSU that you already know you need.