Here's a confusing one: Motherboard won't post with 2 psus, but works with 3rd?

J Macker

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Hey guys,

I built a computer for a coworker about two months ago.
The specs:
Biostar H77MU3
i3 2100
2x4GB Gskill Sniper DDR3 1600 1.5v
Antec TruePower Trio 550w (2006, A1, reused from his previous computer)
120gb ssd

The motherboard has integrated video, so no gpu. It's a very basic computer obviously.
Now, it was working fine like this for the past two months approximately. He brought his computer back to me because I forgot to backup the Outlook data file with their archived emails (who uses outlook for personal email?! GMAIL, come on!). Now my task is to try and recover the .pst file after the drive has been formatted.

Anyhow, I plugged the computer in and it wouldn't post.
Tried clearing the bios, no post. Disconnected 24-pin connector, shorted green to black and the psu started right up. During the many times I unplugged the 24pin connector and reconnecting (a dozen perhaps), I got it to post twice. So it did work, just not reliably. One time it posted when the mobo was in his antec 300 case, and another time it posted when the mobo was out of the case sitting on an old Ratpadz.

Next, I tried an Antec NeoPower 650w that I was using in my test bench with a new ECS H61 motherboard with another i3. The NeoPower 650w works fine, I've used it for testing many times.

Still, no POST. The 650w psu instead made a quiet clicking sound. I didn't notice it last night, but just noticed it tonight. I tried his Antec 550w psu with my new ECS H61 motherboard. It booted right up.

At this point I was quite perplexed and confused. I tried different RAM, I uninstalled his Biostar H77 board from the case and tried posting with it sitting on an old Ratpadz (not the best non-conductive surface but it works fine). I tried just shorting the jumper with no case power switch. The Biostar H77 would not work reliably.

After meddling with it last night for an hour and another hour tonight, I finally tested it with a third psu, this time an Antec Neo ECO 520C (the label looks like this, but the background color for the vertical 520w is brown, not red as shown in the newegg pic). The Biostar H77 board now boots consistently.

So what is wrong? This is not a riddle, I am seriously confused. Why does the Truepower Trio 550w work fine with an H61 board but not this Biostar H77 board? It used to work just fine with the H77 board before transportation.

Why won't the Biostar H77 board work with the Neopower 650w?

Why does the Biostar H77 board work with the Neo Eco 520C but not the other two psus?

*edit* I also tested some new RAM. Samsung 1.35v, a single 4GB stick. The RAM works fine with the Neo Eco 520w psu. I left the computer on all night with the Samsung RAM last night after I posted this thread.
 
Last edited:

evilsofa

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When you are switching in a PSU, are you also switching in all of the power connectors that came with that PSU? I'm talking about the SATA and molex power connectors, not just the 24-pin motherboard power connector.
 

colinstu

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The red switch on the PSU is set to 115v (110-125v) ... right? I remember having a computer's power supply make a ticking sound when I turned it on and noticed the switch was set to 220-240v.

Sorry I got nothing else to say. Real random issues there :(

EDIT: What work surfaces are you testing both these motherboards? Not on any kind of foam or anti-static bag that comes with the mobo right? Those will short out the board.
 

Dangman

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The red switch on the PSU is set to 115v (110-125v) ... right? I remember having a computer's power supply make a ticking sound when I turned it on and noticed the switch was set to 220-240v.
All three PSUs have APFC so they don't have that red switch at all.
 

J Macker

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EDIT: What work surfaces are you testing both these motherboards? Not on any kind of foam or anti-static bag that comes with the mobo right? Those will short out the board.

I tested with the H77 board installed in an Antec 300 and also while the motherboard was sitting on an old Ratpadz. I got it to post a couple of times as I mentioned, in both the Antec 300 and while sitting on the Ratpadz on the table.

When you are switching in a PSU, are you also switching in all of the power connectors that came with that PSU? I'm talking about the SATA and molex power connectors, not just the 24-pin motherboard power connector.

I did not have any sata/molex connectors plugged in during this testing. Yes, I switched both the 24-pin and 4-pin connector each time I tested a PSU. All 3 psus work fine with my H61 board sitting on the Ratpadz.


This one has me confused. Hopefully somebody can shed some light on the subject.
 

staticlag

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Have you checked the motherboard for blown caps?

Have you checked the motherboard/case for any spills?

Sounds to me like a cracked solder joint or blown cap somewhere.
 

Tsumi

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It could be the green pin on the connector not making good contact with the motherboard pin. A small screwdriver or nail might be able to close that up.
 

J Macker

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Have you checked the motherboard for blown caps?

Have you checked the motherboard/case for any spills?

Sounds to me like a cracked solder joint or blown cap somewhere.

I was thinking of that, but the motherboard is working fine with the 520w psu now. So is that really plausible?

No, there aren't any indications of damage to the motherboard. I looked carefully over it for solder connections. There are no spills in the case. I also inspected the 24-pin connectors on both the motherboard & psu to see if any connections were loose. There weren't any obvious loose connections.
 

J Macker

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It could be the green pin on the connector not making good contact with the motherboard pin. A small screwdriver or nail might be able to close that up.

So both the 650w neopower and the 550w TP-3 might have a loose connector, but they work fine on the ECS H61 motherboard?

Sorry, this doesn't seem logical. That is why I'm confused. If any plug connections were bad on the 24-pin connector on the 550w or 650w psus, that would be apparent when I connect them to the H61 motherboard.
 

bbenz33

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I have actually seen this happen before where I had several PSUs and two motherboards and one of the motherboards would not post with the PSU that had been in the system for over a year but that same PSU would power another motherboard just fine. However a second PSU would power the system with no problem. I even went so far as to short the green-black wires while the system was plugged in and that worked fine. I essentially came to the conclusion that the PSU that wasn't working overtime had gotten picky about how much voltage was needed to "complete" the green-black power circuit. I simply had to change the PSU out and use it in another computer.
 

Tsumi

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Maybe something is different about the motherboard pins?

It's just something to test, doesn't really hurt to try and see if it makes a difference.
 

J Macker

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I essentially came to the conclusion that the PSU that wasn't working overtime had gotten picky about how much voltage was needed to "complete" the green-black power circuit. I simply had to change the PSU out and use it in another computer.

Interesting. Thanks for posting.
That could very well be what is happening. The computer is going back to its home today though so I won't be doing any more testing with that motherboard. It's not enough of an issue to dissuade me from using cheap biostar boards for builds for others.

If this were the issue, I find it very interesting that somehow the electrical connection worked previously for an extended period without problem using that 550w TP3, and only now is it having problems. I wish I could test that method of shorting the green to black while it's plugged into the motherboard to see if it would post.
 

flyingears

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Some motherboards have power protection circuitry that interferes with psu power protection circuitry. My enermax galaxy 1250 psu has only worked with one motherboard i own and this is because of incompatibility. If everything else checks out and all components work in atleast one setting then you should simply chalk it up to incompatibility and not worry about it.
 

J Macker

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But again, if it were a true compatibility issue, then the TP3-550w shouldn't have worked in the first place.

The computer worked fine with that psu for at least 2 months.
 

bbenz33

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I can't answer that question, as I had the same quandry where my system was running for almost a whole year. I went back and forth with Asus and even sent my motherboard in for warranty. They promptly sent it back stating it worked just fine. It wasn't until I got another PSU and was able to test it that I found it was some weird issue between the two.
 

bman212121

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I would go with the bad capacitor theory. When the computer got unplugged and brought over it likely had enough time for the caps to completely discharge. Now they don't want to charge back up on some of the PSUs. If you did a quick swap again to one of the other supplies it might actually work again as the board will have enough current on it to still work.
 
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