Not a PSU guru, but I'll throw my $0.02:

For the first question, try to find an online PSU calculator. I know Enermax had one back in the day, and it wasn't the only one. At first glance it should be ok (those PCI/PCIe cards should be fairly low power, and 8 HDDs will draw around 80-100W).

The values are at the low end of the ATX specifications, and I certainly wouldn't be comfortable with that. Where are they going if you put a full load on the CPU & especially GPU? Are you certain the HW monitor is accurate, have you measured them with a multimeter? Have you checked inside the PSU for bulging/leaking capacitors? (They might go bad in 10 years even without showing any sign).

If the voltages shown are correct, the voltages are bit too low and you might need a new power supply. Generally +-5% is acceptable by atx standard. I would check the voltages with a multimeter though instead of trusting what bios says. I think 750W should generally be enough, because I don't see that system using much more than 500W.

Use a multimeter; never trust what the SuperI/O chip on the motherboard (from which most of the various voltage/temperature/etc readings are derived for display in the BIOS and utility programs) is reporting, with an eye on even 75% accuracy to what the real values are.

Also, a 750w PSU ought to be enough for all of that. Being 10 years old, though, you may as well crack the cover anyway to blow out dust and check for aging components.

quicknick wrote:

Not a PSU guru, but I'll throw my $0.02:

For the first question, try to find an online PSU calculator. I know Enermax had one back in the day, and it wasn't the only one. At first glance it should be ok (those PCI/PCIe cards should be fairly low power, and 8 HDDs will draw around 80-100W).

The values are at the low end of the ATX specifications, and I certainly wouldn't be comfortable with that. Where are they going if you put a full load on the CPU & especially GPU? Are you certain the HW monitor is accurate, have you measured them with a multimeter? Have you checked inside the PSU for bulging/leaking capacitors? (They might go bad in 10 years even without showing any sign).

Here's one of said online calculators: http://www.coolermaster.com/power-supply-calculator/

As others said, you should measure these voltages with a multimeter instead. From my personal experience, 4.5ish volts on the 5 volts rail is a bit too low. I've had many hard drives refusing to spin if the 5v rail was undervolted like that.

You should buy a newer (higher quality maybe) PSU. Better be safe than sorry.

I'm actually surprised the voltage numbers are holding where they are. It appears this isn't a group regulated unit as it's not dumping the 12V rail while spiking the 5V and 3.3V rails, however it's evidently operating beyond what's appropriate for it's design. You need a power supply more consistent with current design requirements having a much heavier 12V load.

18A for 12V is really a bit little for that bunch of drives.
Just looked at the open workstation in my workshop with its four drives: its power supply has a rating of 58A at 12V.
As the 12V line is overloaded, the other voltages get pulled down as well.

The voltage readings should be taken with an actually voltage meter the chips on the motherboards are generally very inaccurate. And that power supply should be fine with that build with four 18 amp 12 volt rails just make sure you spread the 12 volt loads over them.

retardware wrote:

18A for 12V is really a bit little for that bunch of drives.
Just looked at the open workstation in my workshop with its four drives: its power supply has a rating of 58A at 12V.
As the 12V line is overloaded, the other voltages get pulled down as well.

If you look at the PSU, it has 4 12V rails that are 18A each which means 72A. Not all drives have to be using same rail.

I think modern power supplies have inflated the perceived need for high wattage in the minds of PC enthusiasts. Bear in mind how much heat is radiated from a 120W light bulb. Now imagine 6 of them trapped in the PC's case. Are you able to toast marshmallows from the exhaust fan? If not, the PSU should be more than capable.

You will know if you're taxing the PSU by ramping up disk and/or CPU usage and watching the measurements. If they dip substantially during activity, then it's a load issue. If they don't, then it's not.

I agree it's either a bad reading from the onboard system management controller, or the PSU's regulation is poorly adjusted.

SirNickity wrote:

I think modern power supplies have inflated the perceived need for high wattage in the minds of PC enthusiasts. Bear in mind how much heat is radiated from a 120W light bulb. Now imagine 6 of them trapped in the PC's case.

I don't think that is a fair analogy, A light bulb (incandescent) dissipates more energy in heat than it does in light. In fact only 2.2% to 5% of the energy comes out as light, so they are 95% plus inefficient.

A CPU/GPU whatever is far more efficient in the amount of energy it uses versus the amount of heat it dissapates.

Ask yourself how much heat a high powered LED generates compared to an incandescent lamp.

Rich

Energy does not disappear, which means that almost all energy that a computer uses turns into thermal energy (except the small amount of light energy from leds and kinetic energy from fans)

LEDs create much less heat because they use much less energy. That's where the efficiency comes from. If you compare a 10W light bulb to a 10W LED (not a "10W equivalent" LED), then it's a fair comparison. 😀

Same can be said for why a Pentium gets about as hot as a low-end Core i3, despite the latter being much faster. Similar power consumption = similar heat dissipation, even though the latter is much more efficient in how much computation it does for that same amount of energy.

Baoran wrote:

retardware wrote:

18A for 12V is really a bit little for that bunch of drives.
Just looked at the open workstation in my workshop with its four drives: its power supply has a rating of 58A at 12V.
As the 12V line is overloaded, the other voltages get pulled down as well.

If you look at the PSU, it has 4 12V rails that are 18A each which means 72A. Not all drives have to be using same rail.

Good catch on the rail distribution. I missed that. Looking at some of the literature (no thanks to ASUS who seem to be pretending they never supplied PSUs), motherboard and peripherals are on 12V1, EPS on 12V2, and PCIe connectors on the remaining two.

Some power supplies have multiple 12V rails on the label only, a quick multimeter check and the dual/triple/quad turns out to be single. Anyways, 18A per rail means over 200W, 8 HDDs will draw nowhere near that.

Thanks a lot for all the inputs. I'm asking for recommendations beacuse recently, I started to have some issues with my rig that might be conncted to a under performing PSU (started after adding last two HDDs and a secondary RAID card). Like "Power surge on hub port" and "Display driver stopped responding and has recovered" errors from Windows, new RAID card not initializing itself one in every two boot ups, Windows starting in non-aero mode...

I did some research and find out that this is not a top of the line PSU as far as the reviews go, but not a dog either:

While the U-75HA is certainly not a bad PSU by any means, it's hard to describe it as anything more than 'average' - a proverbia […]
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While the U-75HA is certainly not a bad PSU by any means, it's hard to describe it as anything more than 'average' - a proverbial plain Jane of the PSU world. It almost feels like ASUS went shopping one day, picked a PSU from the shelf and decided to re-brand it as their own. There really is no 'ASUS' as we know it in the U-75HA, no sign that anybody has actually given any though to how the age-old PSU design used by so many manufacturers could be improved upon, and unfortunately as a result the U-75HA is likely to find it very hard to gain a foothold in an already saturated market.

However, while the U-75HA may not quite have lived up to our expectations it certainly doesn't mean that the power supply should be shunned by those of us who are looking for a no nonsense 750w unit that simply gets the job done. Load voltages were good all the way up to 75% and efficiency came within a whisker of 86% when under 429w load. Only when we pressed it to it's limits did the U-75HA show signs of strain with the +3.3v rail dropping to 3.1v and the +12v3/4 rails dipping 11.70v. While we couldn't get any official noise measurements for the unit due to the noise emitted from our SM-268+ load tester, the U-75HA remained cool throughout the tests and as a result only needed to increase the fan speed slightly.

At present there are no stores in the UK listing the U-75HA; making it impossible to work out where ASUS have positioned the U-75HA price-wise in the market. However, when this information becomes available to us the scoring chart below will be updated.

The Good
- Cool running even at 100% load.
- Up to 86% efficiency.

The Mediocre
- Reasonable stability up to 75% load.

The Bad
- 3.3v rail falls outside of ATX spec at 100% load.
- Nothing to separate the U-75HA from any other standard PSU on the market.

I made the calculations by using the calculator mentioned above and my load is around 600-620 Watts which is above 75% of the PSU's maximum, and according to reviews, that''s beyond its stability envelope, so I might be loading it above the limit of its capability.

To say the truth, it was holding up itself without a fuss with regualar daily use since 2009, but the last 2 HDDs, the SSD, the cecond PCIe RAID controller and GTX770 (upgraded from a 560Ti) was all recent additios, so probably I'm at a point beyond it's ability now.

Just to be sure, I'll measure it's output voltages with a multimeter. I guess I should do it while it is under load, right? I will also check inside for any bulging caps or other obvious age related problems but I'm not an electrical technician in any ways, so ...we will see 😊

I also have a tester jut like the one in the picture below. Are they ok to get some reliable readings?

tayyare wrote:

While the U-75HA is certainly not a bad PSU by any means, it's hard to describe it as anything more than 'average' - a proverbial plain Jane of the PSU world. It almost feels like ASUS went shopping one day, picked a PSU from the shelf and decided to re-brand it as their own. There really is no 'ASUS' as we know it in the U-75HA, no sign that anybody has actually given any though to how the age-old PSU design used by so many manufacturers could be improved upon, and unfortunately as a result the U-75HA is likely to find it very hard to gain a foothold in an already saturated market.

What exactly were they looking for in a PSU? A sparkling personality? I have my own criteria for a PSU (for any application) that reads a little like Asimov's laws for robots:

1) First and foremost, protect the user.
2) Just second to the above, protect the load.
3) Don't pollute upstream.
4) Power the load.

If it does those four things, preferably quietly and efficiently, then it's all I could ever ask for in a PSU. I really don't want or need it to sing or dance or do magic tricks. 😉

The problems you describe could be a sign of failure, though, so I would consider that a data point. By all means, connect your tester and see what it says. If it agrees with your motherboard's voltage readouts, then you have a problem. If it does not, then get a third opinion by way of a good multimeter.

2009 is still relatively young, but it could be a victim of thermal stress (if the design favors silence over thermal management) or flawed capacitor selection.

Bear in mind your calculator is probably giving you worst-case power draw, where all devices are consuming at their peak simultaneously, which is not likely to be a real-world scenario. Your drives will pull the most at startup, but supplies are rated for both continuous and transient duty, and the latter is often considerably higher for a short time. I would expect a 750W supply to be able to deliver 600W continuous, and I would expect a 600W calculated load to be substantially less in practice.

I measured the voltages both with the mentioned tester and using multimeter. Both tests showed that, when not under load, this PSU has picture perfect values in both 5, 3.3, and 12V lines.

I also checked its insides, and could not see anything obviously bad like bulged caps, etc. It was even quite dust free (I regularly blow the crap out of my computers, every 3-4 months or so)

In conclusion, I decided that, either by old age or by design, this PSU is not up to the loads I put on its shoulders. I ordered a new PSU (slightly more powerfull, Corsair RM850i) and my voltage readings are much better now.

The funny thing is, while USB power surge alarms are gone, I still have the boot up glitches with the PCIe RAID controller and still having the occasional "display driver stopped responding" errors 😊

All in all, thanks a lot for all the fish.. err, helpful responses 🤣

Hard to tell from a single picture, but there does seem to be quite a dark dust bunny growing around the heat sink next to where the cables exit. It's also the caps under that bundle of wire that usually fail, in my experience. I haven't seen the mains caps (large ones on the other side) fail myself -- though I'm sure it happens. They take a lot of abuse.

I've had the display driver issue twice before. Once when I had a card that was on its way to the grave, and another time when I just had some buggy drivers. So it could be either of those. If your GPU fan is clogged with the same drier lint and tar combination that's collecting in that PSU, it might need a hit or two from the ol' can of air. 😀