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Motherboard voltage

Posted on 2002-04-18
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Last Modified: 2012-06-27
I just bought a new PC with these specs: AMD Athlon XP 1700+, Asus A7V333 (KT333) m/b, 256MB Kingston DDR Ram, Asus V8200 GeForce3 Ti200 gpu, Maxtor 60GB hdd with ATX standard casing plus power supply.

Upon installing Asus Probe m/b monitoring program, I received a warning on one of my 3 m/b voltages! the +12V specs is reading 13.311, thus causing the error. The default treshold setting recommmended is 12+/-10%.

My questions: What is this 12V used for? What might be the causes for this voltage fluctuation? What is the damage for PC if I chose to ignore this warning? How to overcome this problem?

Please help asap.

Thanks...
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Question by:pennyroyal
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by:pjknibbs
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13.311 isn't that far out of gamut (12V + 10% = 13.2V), so it may not be a problem. As for what it's used for, usually the 12V line is used by devices like hard drives to power their motors--as far as I know there's nothing on the motherboard which requires that voltage, although I'm willing to be proven wrong.
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by:pennyroyal
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What a coincidence! A few months back, my one year old hard disk on my dad's PC couldn't power up. Your comment triggered some new findings for me. But can you confirmed that this 'little' extra voltage wont damage/short my hdd in a long run?
Please feedback and try to answer those questions posted earlier, anyone!
Thanks...
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by:jhance
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You need to check the specifications on the device to determine whether or not 13.3 is out of spec.  As pjknibbs noted, 13.3 is within 10% so that would be just fine for a +/- 10% tolerance requirement but would be OUT OF SPEC for a +/- 5% requirement.  

The only way to KNOW is to check the specs...

I'll just note that most hard drives I've seen call for +12V +/- 10% and +5V +/- 5% so for a HDD, you are OK.

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by:Macrobeat
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The 12 V line does go to the motherboard as well.. and it is used. For example your PS 2 ports - while they draw very little current - they actually draw this from the 12 V line to the motherboard. There are other devices that draw on the 12 Volt cable though manufacturer listed tolerances tend to be very conservative and you can go a bit higher than the 10% variance.

Are you using a quality power supply? Is it AMD approved. Is it at least 300 watts? Some PC manufacturers cut corners on the PSU. If yours has... take the trouble to change the PSU - it will be worth it in the long run.

You can check your make of PSU at AMD's site:
http://www.amd.com/us-en/Processors/TechnicalResources/0,,30_182_869_1039^1053,00.html

Macrobeat :-)
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by:highstar1
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12volt cards ISA used to be common in the old days. Old MB 8088 days used to use as well. ISA,EISA and PCI ports are required to have the 12V available as part of the standard. The newer MB's internally have no use for it. AT MB had only +/-5V and +/-12V lines. ATX adds 3.3V for the newer processors and ram. Helps keep the MB cooler.
AT MB had to reduce the voltage to 3.3 for the pentiums.
The process of reducing the voltages produce alot of heat.
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by:willinois
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Power supplies are not all that expensive.  I would get and install a new quality one instead of risking a MB fry.
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by:willinois
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by:NickLo
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The power supply is regulated and only work with a small load connected.  The serial ports (RS232c) are supplied at -12V and converted to +3V to +5V for the internal logic circuits. The +12V line supplies the disk drives.  If you are experienced enough, then either replace the voltage regulator or replace the power supply.
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by:pennyroyal
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so far, info i've gathered:
1. 12V is used in hdd motor, ps2 port, serial/parallel ports, ISA standards slots. Any PCI slots?
2. The cause of this fluctuation is bad power supply or bad voltage regulation. Is there any other reason? Could the mb be faulty and giving this extra voltage?
3. To overcome this problem, changing the power supply is recommended.
4. Continuous usage with this extra 0.1V wont be much damaging, but might fry my mb if things get worse. How about those hardware that is using this 12V? Will this extra voltage damage/short my hdd for example?

The power supply I've bought is rated as 300W. I think this is enough. But I'm not so sure about the manufacturer and whether it's AMD certified or not. Is there a way for me to check/measure the actual voltage rating myself? Can't really trust what is written on the manufacturer sticker, right?

Again, thanks in advance for all the comments thus far. I've increased the points again to get more detail info as I still have doubts on this problem.
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by:kiranghag
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dont rely on the software reading. they may not be 100% accurate.
check the voltage with a multimeter.
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by:pennyroyal
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How & where to determine the place to measure the voltage?
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by:willinois
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Stick the multimeter pins into the back of the power jack going into the motherboard.  Keep black to black so you don't short anything out.  Check the voltages with the power on, but be careful.
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by:Macrobeat
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Software is not reliable for giving you the voltage. You'll have to use a multimeter. If you don't have one then get a local shop to test it for you... or invest in a multimeter.

See: http://www.pcpowercooling.com/products/power_supplies/terminology/terminology.htm
for definitions. Don't take anything for gospel truth (I have trouble with them defining current in volts. The last time I checked the unit of measurement was amps - but this is a useful site anyway)

The Power Good signal they talk about comes off the yellow cable on computer PSUs.

Your over voltage protection should have kicked in to cut off the supply if it was too much. This applies to output off off the "step down" transformer in your PSU i.e. your 12 V line but if your PSU doesn't even have a name on it I wouldn't bet on it being the best in the market. Change it.

This page should answer all your other questions about power supplies for the PC:
http://www.pcguide.com/ref/power/sup/index.htm

And it'll explain why it's so important to have a good PSU.
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by:NickLo
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Reading through the lines, I understand that you are not familiar with electrical or electronic terms or computer hardware.  My advice to you is to return your computer to the shop you had purchased it from and let the experts check it for you.  If you remove your computer cover, you will forfeit any guarantee you may have.  An expert will look inside the computer for a spare power supply female connector.  This is a small rectangular block with 4 holes and 4 wires connected to it.  The hole with the yellow wire is the +12V supply.  The two black wires are connected to the two in the middle.  These are the ground connections.  The one with the red wire is the +5V.  To measure the 12V supply, you switch on the computer and using a multimeter set to read d.c. volts, insert the Red prod into the hole with the yellow lead and the black prod inserted into one of the two holes in the middle.  Repairing computer power supplies is very dangerous if you do not know what you are doing(they can explode into your face).  If there is no spare power supply socket, then I personally start the computer and then pull out the one which supplies the floppy disk drive, measure the voltage and then connect it back to the drive very carefully.
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by:willinois
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NickLo,

You are right, the Molex, and the mini connectors are easy to find voltages on, and if someone in inexperianced with the use of a multimeter should not try what is suggested here.  If the system is warrantied then it is best to have those people check it out.

The mb monitoring probe wont be checking the molex and mini connectors, it will be analyzing the mb power supply which may vary...specially if the power supply is going bad.

Macrobeat..."Your over voltage protection should have kicked in to cut off the supply if it was too much".  Don't always count on this happening correctly.
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by:Macrobeat
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>> they can explode into your face

Capacitors also store a charge and can give you a nasty shock even if the power plug is out. So, do be careful.

>>Macrobeat..."Your over voltage protection should have kicked in to cut off the supply if it was too
much".  Don't always count on this happening correctly

That's exactly what I said :-) My point was that if it didn't happen on this PSU then the PSU couldn't be a very good one :-)
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by:pennyroyal
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Dont worry guys. My understand of electricity is A ok. I'm an E&E degree grad here :) Just wanna make sure things before really doing it. Multimeter is like a pen in my line of work now. So, looks like I'll do some measure of the power supply and see what I find. I'll also go through the suggested website to get more info. Thanks...
But still, what are the likely damages if I chose to ignore this little over voltage? What is the % of it to happen?
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by:pjknibbs
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Frankly, if the overvoltage was going to be a problem it would already have manifested itself by something burning out--I seriously doubt such a tiny excess voltage (we're talking 0.1V out of spec here!) is going to cause long-term problems, at least not until long after the point where the components in question fail for other reasons. (For example, you are FAR more likely to suffer a head crash or electronics failure on a hard drive than you are to burn its motor out, and we've already established that's the main use for the +12V line).
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by:pennyroyal
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Pjknibbs, thanks for your reassurance. I guess you really help me clear my major doubt. But lastly, can you confirm that your statement will also apply to long term usage of a pc, eg 2 or 3 days non-stop.
One thing to note here is although the voltage is over the spec limit, it will still stay constant within +/-0.050. In voltage term, I think it'll be alright. A voltage surge is what we want to avoid!
Thanks again thus far...
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pjknibbs earned 300 total points
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Both my PCs at home and all the PCs in the office run 24/7, and none of them has yet had a problem which could be attributed to overvoltage. In fact, the most likely component to fail when running a PC constantly is the CPU cooling fan (or the equivalent on the graphics card, if there is one), and these fans don't use the 12V line at all!
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by:pennyroyal
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Alrighty then... With pjknibbs assurance, I'll close this topic. Learned a few things and thanks for all the comments received.
I'll ignore this 'little' overvoltage and carry on using my new pc without fear for now. Maxtor hdd carries a 3 years warranty as well. But hope that wont be needed.
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by:NickLo
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I am glad you have accepted an answer but it is not just the voltage surge you will have to avoid.  13.3 volts is high (This is outside the 10% tolerance) for a 12V power supply.  It means that some components will run slightly hotter than intended and motor driven devices such as the cooling fans and disk drives will run slightly faster which means that your computer's life span will be greatly reduced.  The starting current ie the current taken by the motors used in the computer will be high and also the surge current during the instant of switching on, will be high.  You have a 3-year warranty but if the motor on your hard disk burns out, you will lose a lot more than just replacing the hard disk.  Since you have decided to ignore this high voltage, then my advice to you is to keep copies of your work on the computer.  If it was my computer however, I would have definitely returned it to the supplier and insist in changing it or replace the power supply.
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by:pennyroyal
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NickLo, thanks a million for your reply. Your comments made me think twice now. Actually, I've thought of the same thing as losing my datas than just exchanging my hdd. I think I would measure the voltages soon and if the reading is correct and over voltages detected, I'll dismantle the power supply and exchange one from the shop I bought. I hope the shop won't make a big fuss and wouldn't change one for me. Will certainly update my status then. I guess I'll have some free time over next weekend to do this. Thanks again...
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