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+5 volt fluctuation on TX750W


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I have a TX750W in a fileserver with 8xsata disks.


I recently upgraded the motherboard, and so powered up only with the motherboard connected after installing to test. The machine kept rebooting every few seconds. I tried another power supply and everything was fine.


Using the TX750W and managing to get into the BIOS showed the +5 fluctuating from about 4v to 4.8v in the BIOS monitor page.


I powered off, attached a few hardisks and then the system stopped rebooting, and the +5v was steady (@ about 5.1v)


Is this expected behaviour ? Shouldn't the +5v be steady when just powering the motherboard/ram and CPU ?


This has caused me hours of messing around. I first thought my ram/motherboard was faulty :/


Motherboard is an asus p5ql-vm epu

cpu is q8200

4gb of corsair XMS2 memory

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Before I had made this post I had submitted a RMA request. However the power supply is currently running with motherboard/cpu and 8 harddisks. It doesnt work though with just the motherboard and the power supply (the voltage issue as I mentioned).


Could any corsair technical support comment on this ? Should the power supply give a stable voltage when a small load is on it (motherboard/ram and cpu)?

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Testing with a multimeter:


First I tried with motherboard and 8 drives connected. everything switched on, and power supply reported 5.9v on the +5v (recording taken from molex connector). No problems here.


Then i disconnected everything and tried when the power supply was connected to three drives (using a paperclip between green/black to make the PSU switch on).


Powered on and +5 reported around 5.9. drives started spinning up, then after a few seconds they spun down again, and +5 was showing 4.2v.. switched off and connected an extra 2 drives, and switching on the power supply showed around 4.2v again, and the drives did not spin up.


When power supply was only connected to the motherboard, it showed 5.9 on the +5v, but after a few seconds fell (to 0 as the machine power cycled). rinse and repeat.


I'm assuming the power supply should just work with a few drives on it right?

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Yes thanks. Just got it. Shame your returns is international postage from here, as its going to cost a fair few quid to post it back :/ The machine runs as a backup server that some of my co-located machines back up to hourly, so I have to try and borrow a power supply from somewhere. Would be great if corsair offered some advanced replacement service as western digital used to (taking a payment sending a replacement, and then refunding it once you return the damaged goods).
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