Overvoltage on startup....bad PSU?

[Dr3wStx]

This machine was running fine for the longest time, untill a few weeks ago when I turned it on and got over voltage bios beeps and it quickly shutdown. I was forced to buy a new PSU (Safe Power 450W) about 3 months ago because the old one died a spectacular death
Now this ones giving me issues

The processors are actully Athlon XP 2400s modded into MP 2600s useing the liquid trace trick.
according to asus probe I've got a low +5V line at 4.945V...could this be the problem, since Athlons pull most of their power from the 5V?

Mesurments taken every 5 seconds....

I can get around the problem by powering it on and off till I get the post beep, but that can take up to 15 trys sometimes

Real pain in the ass....any help would be great.

 

[Ice Czar]

sounds like a generic doorstop PSU
one I dont recognize
got a link?

while the readings are in spec
the software isnt running at spinup
and it could easily have a voltage regulation issue
or simply a bad Power Good Signal

When the power supply first starts up, it takes some time for the components to get "up to speed" and start generating the proper DC voltages that the computer needs to operate. Before this time, if the computer were allowed to try to boot up, strange results could occur since the power might not be at the right voltage. It can take a half-second or longer for the power to stabilize, and this is an eternity to a processor that can run half a billion instructions per second! To prevent the computer from starting up prematurely, the power supply puts out a signal to the motherboard called "Power Good" (or "PowerGood", or "Power OK", or "PWR OK" and so on) after it completes its internal tests and determines that the power is ready for use. Until this signal is sent, the motherboard will refuse to start up the computer.

In addition, the power supply will turn off the Power Good signal if a power surge or glitch causes it to malfunction. It will then turn the signal back on when the power is OK again, which will reset the computer. If you've ever had a brownout where the lights flicker off for a split-second and the computer seems to keep running but resets itself, that's probably what happened. Sometimes a power supply may shut down and seem "blown" after a power problem but will reset itself if the power is turned off for 15 seconds and then turned back on.

The nominal voltage of the Power Good signal is +5 V, but in practice the allowable range is usually up to a full volt above or below that value. All power supplies will generate the Power Good signal, and most will specify the typical time until it is asserted. Some extremely el-cheapo power supplies may "fake" the Power Good signal by just tying it to another +5 V line. Such a system essentially has no Power Good functionality and will cause the motherboard to try to start the system before the power has fully stabilized. Needless to say, this type of power supply is to be avoided. Unfortunately, you cannot tell if your power supply is "faking" things unless you have test equipment. Fortunately, if you buy anything but the lowest-quality supplies you don't really need to worry about this.

POWER SHMOWER by Mike Chin

or How PSU Power Ratings Mean Almost Nothing

A frustrating fact about PSUs is that there does not appear to be a stringent or regulated standard for reporting, advertising and labeling rated power. This is despite the existence of standards like ATX2.03 or Intel ATX12V.

There are well-established standards for measuring and rating HDD capacity, an engine's horsepower, or the heat generated by a furnace... but not one for how much power a PSU can deliver. There are so many cases of people with "450W" PSUs having power stability issues running a system that can't possoibly draw more than 150W. And "300W" units that keep running where the "450W" units are faltering.

It's not just about bad PSUs vs better ones. It's a dumb situation caused by uncontrolled marketing competition. Real regulation would bring PSUs out of snake oil territory and into a more sensible consumer-friendly terrain.

There are many ways PSU makers fudge to make their units seem more powerful.

1) Out and out lying. You add up the power on all the lines in many PSUs and they fall short of the rated power by 10, 20 30W or even more.

There are more sophisticated ways:

2) Limit the AC input voltage to a very narrow tolerance. The best PSUs are able to deliver their rated power given a decent range of AC input power, say 90~130V for a 120V unit. It's much more demanding to produce 300W w/90VAC input than with 120VAC, so what some PSU makers will detail in their tech specs (usually not in their consumer brochures) is to specify 115-120VAC for input power. A PSU specified this way will not deliver full power if the AC voltage sags, if there is a brown-out. Surely it causes instability more often than a PSU rated to deliver full power with 90-130VAC.

3) Specify a low operating temperature for rated output. This is quite common, but again not often seen in consumer brochures, but rather tech spec sheets provided usually only on demand by engineers or corp buyers. A typical PSU operating temp statement is somthing like this:

0ºC ~25ºC for full rating of load, decrease to zero Watts O/P at 70ºC

Examine what that says. Full power (let's say 400W) is available when the unit is at 0ºC ~25ºC. Hmmm. Think about this.

Have you ever felt air blown out of a PSU in a PC running absolutely full tilt (which it would have to do to get anywhere near 400W output) that felt cool to the fingers? 25ºC airflow would feel exactly that: Cool, given that normal body temperature is 37 °C.

So this PSU cannot deliver full rated power when its temperature goes over 25ºC. OK, what happens to the max power output capacity above that temp? It decreases gradually so that by the time the PSU temp reaches 70ºC, the PSU cannot deliver any power at all. So if you assume that this power drop as temp rises is linear, then max power capacity will drop by ~9W for every degree over 25ºC.

Now having examined as many PSUs as I have over the last 2~3 years, I have to say there's not a single PSU in ANY PC I have ever used or examined that would not measure at least 30~35ºC almost anywhere inside the PSU under almost any kind of load. And if/when it is pushed, 45ºC is nothing at all, especially for or near hot running components like voltage regulators.

So let's say 40ºC is a fairly typical temp inside a PSU. This 400W rated unit would actually be able to deliver a max of just 220W at that temp. Hmmm. Interesting, isn't it? At 50ºC, the available power would drop to just 130W. No wonder some PSUs have 3 fans each capable of 50 cfm!!

Here's a simple fact: Really high quality PSUs are actually rated for full power output at as high as 40ºC. The trick is get a hold of the spec sheets that tell such information so you can compare apples to apples. Or ask.

or

from dansdata

Unethical PSU Marketing 101.

Here's how to make overly optimistic power supply specifications. It's really simple.

First, power the thing up. You can make an ATX power supply that isn't connected to a motherboard turn on by grounding pin number 14 on the big motherboard power connector. It's easy to spot that pin, because it's the only one with a green wire going to it.

Use any handy bit of wire - like the paper clip in this picture - to connect pin 14 to any ground contact. The ground contacts are the ones with the black wires going to them. Presto, the PSU will turn on.

Now, break out your brick-sized power resistors and load the heck out of one of the output rails - the +5V rail, for instance. Measure the current as you increase the load, until the voltage sags unacceptably far below the rated voltage.

How do you tell what an unacceptable voltage sag is? Well, you could choose a nice conservative small permitted sag - say, 0.1 volts - so that your results are genuinely useful to your customers. Or you could just ignore the voltage and say that when a fuse (or some other component...) blows, that must have been the limit, right there.

OK. Now you've made a big fat amperage number for the +5V rail. If you blew up the PSU in the process, get another one, and repeat the process for +12V and +3.3V, and for the low current rails as well.

On no account, though, should you test more than one rail at a time. This is the key to the whole scam.

A big beefy PSU may be able to deliver 50 amps (say) on the 5V rail when nothing else is under load, and 25 amps (say) on the 12V rail when it's similarly all alone. But the 12V and 5V rails together may only be able to deliver, say, 350 watts between them, when they're both under load. Watts equals amps times volts.

In a real PC, all of the power rails will always be under load together.

But you're not testing what the PSU can really do - you're making pretty numbers for the sales brochure!

So test all of your rails alone, get an amperage figure for all of them, multiply that figure by the voltage of the rail it came from (the nominal voltage, not whatever the voltage had sagged to as the PSU pumped electrons through the dessert spoon you'd soldered to the circuit board), then take all of the resulting wattage figures and add 'em up. That's a wrap, folks. Ship it!

so actually run the numbers and post back

 

[larrymoencurly]

I've got a low +5V line at 4.945V...could this be the problem, since Athlons pull most of their power from the 5V?

That's only 1% below perfect and is nothing to worry about, but can you trust that reading or the others? Because software voltage readings are notoriously inaccurate sometimes and should always be verified with a digital multimeter.

Athlons don't pull most of their power from +5V but from the Vcore source, which itself uses either +5V (many dual Athlon boards, especially those with an auxillary 6-pin connector) or +12V (square 4-pin connector or IDE drive power connector).

I'm not familiar with the Safe Power brand, so what are the numbers printed under the CSA (www.csa.ca) and UL ("RU", www.ul.com) marks? Only the very worst PSUs won't list those numbers.

 

[Dr3wStx]

I don't know what I was thinking what I made that first post but its a 450W not a 400W. My mistake
Anyways.....

I ran the number while ago, I have a need for about 345W, that caculator is a bit tough to use since none of my componets are actully listed on there, but I made it as close as possible.

as for the CSA LR90681-6 Level 3

Also I'll list the rails just for referance
+5V..... = 34A
-5V ..... = .5A
+12V... = 18A
-12V ....= .8A
+3.3V.. = 28A
+5VSB = 2A

I was lookin at the CSA site and I was thinking I could get info from there, but I cant find it??

 

[Dr3wStx]

I still don't know if its the PSU or not....

 

[BillR]

I still don't know if its the PSU or not....

I have three of those Asus boards, all with hard modded Barton 2500’s pumped to 3200. I use Antec True power 430’s and they run 24-7 doing distributed computing. Each has a gig-0-ram and an 80-gig WD hard drive and of course all the usual fans to keep those suckers cool.

The only problems I’ve had similar to yours are the voltage regulation on those boards is a bit dated and doesn’t seem to like the newer higher current CPU’s. My fix was not to use the Asus voltage selectors but instead I hard modded the CPU’s. That made it all rock stable.

I also noticed you are running an ATI 9800 Pro. I can only get that card to work in one of the machines no matter what PSU I use. After doing a bit of multi meter work I find that the AGP buss of that board is strained with some of the newer video cards. A mere 2 tenths of a volt makes the difference. I did some research with Asus and they agreed that the buss wasn’t exactly designed for that kind of card, it was a “server board after all”. They had little to say about the Bartons

Anyhow, just for S’s and grins you might want to try an older video card and see if that makes a difference. My Asus probe program was doing the same as yours, which is what caught my eye in this thread.

Oh, if you don’t have the latest beta bios you should, it helps a bit.

Just some thoughts