12V rail giving only 0.6V - replaced PSU, so what is wrong?

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Hi, I'm afraid that my old thread was maybe too general and didn't get much attention as a result, so I want to ask one specific question from it.

Reference: http://forums.overclockers.co.uk/showthread.php?p=10115316

I have taken readings with both CPU-Z and SpeedFan of the voltages supplied to my system.

On the 12V line, it never seems to be 12V. For example, I just took some readings, and here they are:

CPU-Z:
1.22 Volts [0x4C] (CPU VCORE)
1.84 Volts [0x73] (VIN1)
3.34 Volts [0xD1] (+3.3V)
4.92 Volts [0xB7] (+5V)
0.64 Volts [0xA] (+12V)
-4.03 Volts [0x3F] (-5V)
5.05 Volts [0xBC] (+5V VCCH)
3.26 Volts [0xCC] (VBAT)

SpeedFan:
1.15V (Vcore1)
1.84V (Vcore2)
3.34V (+3.3V)
4.92V (+5V)
0.58V (+12V)
-16.67V (-12V)

-5.86 (-5V)
5.05V (+5V)
3.26V (Vbat)

As you can see, +12V line is reading only 0.64V, and the -12V line is at -16.67V!

:confused:

I thought this might be the PSU, but I got an RMA on it, installed the new one, and I have exactly the same problem.

1. Am I correct in assuming that the 12V should be reading 12V at all times? Presumably the draw on it in Amps varies dependant on load, but the voltage should be constant?

2. What could cause this apart from the PSU? What is the motherboard involvement in power regulation?

3. Could any of you please run SpeedFan or similar and confirm if you are seeing 12V on the +/-12V lines?
 
Soldato
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I should try checking on your BIOS rather than trusting those readings. Surely your computer wouldnt be booting up if the voltages were that far out!

If its not the PSU then its the voltage regulators/sensors on the motherboard thats probably gone.

PK!
 
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Indeed a good idea, however unfortunately the my Gigabyte BIOS (I have tried the F2 version it shipped with, and I have flashed to the latest F4 too) only shows a green 'OK' next to the voltages, which is pretty unhelpful, hence why I have had to resort to taking software readings.
 
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I had this, it was a short. Check your mobo screws and stand offs. Try taking the board out of the case and plugging in. Mine ended up being the leg off my spot fan shorting a couple of legs on a chip, insulated it and everything reads normal now.
 
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As cooljimy84 says if your PC is stable then I wouldn't worry about it in the least, software readings of rails are notoriously inaccurate and if you were really getting 0.64V on the 12V rail your PC simply wouldn't boot.

I don't have Speedfan on this computer but the ATX standard allows a tolerance of +-5% on the major rails and I know my computer at home is within that. :)
 
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i take it ** pc if perfecly stable... if so then it's prob just fan speed and CPU-z reading it wrongly

Unfortunately it is very unstable - I am getting BSODs as detailed in my older thread.



At first glance it appears to be a video driver problem, but I want to understand the strange power readings first as I suspect they may be the root problem.

Edit: having said that, I am on the verge of RMAing my RAM and Graphics Card, and going out to buy a new motherboard (I threw the box etc out).
 
Soldato
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buy a volt tester from a electric shop.....

The only way to be really sure.
Test at the 12v plugs while both connected and disconnected to the mobo and all other components.
Read up on how to power up the PSU without the mobo, you'll find lots of threads/articles on this.
I have to say that if you've replaced the psu already then it's my money's on the mobo or gpu.

Keep posting so we can help you get it sorted.
 
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I purchased a new motherboard (Asus P5KC) to eliminate it as a possibility. The voltages now appear correct, so I suspect that the Gigabyte was not reading it correctly.

However the error is still happening. I have now replaced the PSU and the mobo, so the problem must be with the RAM or graphics card. I am seeking a replacement from BFG for the 8800GTX OC2. This thread can now be considered closed as the issue with power readings has been sorted.
 
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