PSU works with one motherboard but not others

Toggle sidebar Toggle sidebar
P

prestonhymas

Prominent
Jan 14, 2018
8
0
510
Okay, so I've been building a PC for the last month and I've never gotten it to turn on. The first boot blew out my old Corsair 500W PSU, so I bought a new EVGA 750 GQ. Nothing. No lights, fans, beeps, ect. Figured dead mobo, so I exchanged. New Mobo behaved the same. Thought I was extremely unlucky with motherboards, so I returned and got a different brand. Third mobo, exact same thing. No way I've gotten three DOA motherboards in a row.

This whole time I've suspected the motherboard because the PSU works fine when I plug it into my old rig, but decided to look more closely at the PSU anyway. I plugged a fan directly into the PSU instead of through the mobo and it does not turn on. This means the PSU is for some reason not putting power into the new components, but will do so for the old ones.

I dropped it off at a computer repair shop that does free diagnostics, and according to the tech, the PSU doesnt have a 5 volt ground. I'm not a computer expert--I just plug things where they should go--but that sounds like an issue that would prevent any system from booting, not just x470 motherboards?

Components:
Gigabyte x470 Aorus Gaming Ultra
Ryzen 5 2600x
GTX 1070 ti
HyperX Fury DDR4 RAM
EVGA 750 GQ

Do I need to get a PSU made specifically for ryzen 2 or something?

EDIT:
Just picked it up and spoke with the tech face to face. He used two meters to measure the PSU and both said the same thing. The light for the -5v line didn't light up. The +5v line did. Again, I don't really know the implications of this, but that's the specific reason they gave for why it's not powering on.
 
Sort by date Sort by votes
Eximo

Eximo

Titan
Ambassador
May 27, 2010
25,839
4,186
139,340
I would question how they determined that. Fans don't run on 5V, so a missing ground there would still spin a fan up. And you say this PSU powers your old rig correctly?

No there is no special requirement for Ryzen. Standard ATX.

Do you have a multimeter or voltmeter? Fairly easy to test an PSU for open circuit voltages. 12+, 5V+, 3.3V+, -5V, -12V. There should be a common ground, and if they determined they were getting open circuit on the "5V ground" then it should have been relatively simply to locate another.

Did you take your new components to the shop and ask them to power them with one of their supplies? Would be a quick way to see if you have some weird incompatibility.
 
Upvote 0 Downvote
P

prestonhymas

Prominent
Jan 14, 2018
8
0
510


unfortunately I don't have a volt meter and the place I dropped it at didn't have a spare PSU laying around. They said when they tested the PSU with their meter all but the -5v lines lit up? I guess that's bad? Should my PSU have current running through the -5v rail? But why would the power work with my other motherboard if that's a problem? It just doesn't make sense to me why the power supply would function with one set of components and not the others. It's 750 watts, which should be over kill.

They recommended getting a refund on the PSU and getting a different one, but I dont want to send back a functioning piece of equipment. I've already sent back two motherboards that I now realize probably weren't the issue.
 
Upvote 0 Downvote
Eximo

Eximo

Titan
Ambassador
May 27, 2010
25,839
4,186
139,340
-5V isn't that common these days. PCs almost exclusively run on 12V+ and 5V+ these days. Part of the older ATX standard, more or less a consequence of the way PSUs work it will output -12V certainly off the transformer after it is rectified. Many newer power supplies use DC-DC converters to get 5V, so they might skip -5V.

A cheap multimeter is about $10-15, so if you don't have one you should consider picking one up.

So my issue with your situation is that it powers your other system just fine? That says it isn't the PSU at all.

How have you built this computer? Typical practice would be to breadboard it with only the CPU and memory in it to see if that works, then slowly start connecting things. If any one of the components has died and is producing a short, it will prevent the PSU from powering up.
 
Upvote 0 Downvote
P

prestonhymas

Prominent
Jan 14, 2018
8
0
510


Is it possible for the CPU itself to be causing the short? So far I've ignored the CPU as an issue because according to the tech support I spoke with at MSI the motherboard should power on and give error lights or beeps to indicate a bad CPU or RAM. They would stop it from posting, but not from drawing power. However, it was on their advice that I sent the first two motherboards back, and at this point I'm fairly certain they were never the problem. Not sure I trust their judgement.

I've breadboarded in the past and nothing has ever spun up, even for just a second. Even outside the case, single stick of ram, jumped by connecting the power pins with a screw driver the board stayed off. It was at this point the tech told me the motherboard was dead and to send in for an exchange/refund. I've had an issue in the past while putting together a build where fans turn on briefly then shut off. Once it was a dead CMOS battery, another time it was a bad PSU. Never have I had a problem with no power at all.

If I were to take the CPU and RAM out entirely and just plug the board in on its own, would it power and give me error lights? Or would it simply damage the board? And would I want to use the 24 pin and 8 pin connectors, or just the 24 pin since there'd be no CPU? In my head, if I get power draw without the CPU, but no power draw with the CPU, that would mean the CPU isn't just not working in the normal sense, but is actively causing a short and telling the PSU not to send power. This is the only way I can think of to test the CPU without access to another AM4 processor.

If it is the CPU, I need to know before my 30 return window closes, and that's coming up pretty quick. This is what I get for making late night impulse purchases.
 
Upvote 0 Downvote
Eximo

Eximo

Titan
Ambassador
May 27, 2010
25,839
4,186
139,340
It shouldn't damage the board to run without the CPU. Just won't be responsive, but the fans and such would kick on if there wasn't a power problem.

You can just try unplugging the CPU power, I have seen that done. That motherboard had RGB lighting so it was pretty easy to tell it was working. I believe their problem was a mis-wired SATA power cable.
 
Upvote 0 Downvote
Eximo

Eximo

Titan
Ambassador
May 27, 2010
25,839
4,186
139,340
This is when having a shop with compatible parts comes in handy. If they could test your CPU you would know.

Since you don't know, maybe just try and RMA the CPU to get that started. You aren't really losing anything there.
 
Upvote 0 Downvote
P

prestonhymas

Prominent
Jan 14, 2018
8
0
510


Yeah, I dropped it off at another shop this morning. They think it's the motherboard, but they also didn't test it with another AM4 processor or put my processor in a board they know is working. So I'm going to exchange both the board and the CPU. The board is easy because it was from amazon, but I'll have to deal with an ebay seller for the CPU, which is why I've been loathe to send it back without confirmation it's the issue. Oh well. Worst that can happen is they charge me a 15% restocking fee ($40). This is what I get for spending money I don't have haha
 
Upvote 0 Downvote
You must log in or register to reply here.

TRENDING THREADS

Latest posts

Moderators online

Share this page

COMPANY
RESOURCES
FOLLOW
Top Bottom