# Risk with 3.3v rail out of range?



## qu4k3r (Jul 28, 2011)

Hi,

I have a corsair tx750w since 2 years ago, but I've noticed that voltage on 3.3v rail has been decreasing over time.

I know it must be 3.3v ± 5% which means any reading between 3.135v and 3.465v is ok,
3.3v is an orange wire at "20+4pin & sata connectors only" (not molex, nor pci-e, nor 4+4pin connectors).

My pc is on 24/7 and I've noticed the following...
If pc is on for long time, 3.3v rail readings begin to fall.
I switched pc off for 5 or 10 minutes, then I switch it on and readings go back to normal.

A month ago it was 3.26v idle and 3.22v full load,
but now it's 3.136v idle and 3.072v full load,
and didn't back to normal after doing powercycle.

I have 2 gfx cards(570 + 460) and "full load" means both cards running FAH-gpu.
If I take out 570 and leave 460 only, readings are: 3.182v idle and 3.154v full load.

All voltage reading were made with Everest (don't have a multimeter) and they match idle reading in bios.

Well...
I know the easiest and fastest solution is buy a new psu but...

What is the worst thing could happen if I don't buy a new psu?
Could this problem burn any component?
Which could be the more sensitive to get damaged?
MB & sata drives right? Or am I wrong?

Thanks in advance.-


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## qubit (Jul 28, 2011)

Your PSU is faulty and must be changed. Is it still under warranty?

As the voltage is apparently simply dropping, then you will eventually see a malfunction, but no damage to your PC. However, it may be spiking, which you can't see and this may well damage your PC.

Running a faulty PSU is never a good idea, especially with two graphics cards.

I don't know what devices use 3.3v nowadays, so the PC may not notice the problem at all.

Using a failing PSU is never a good idea, however. The fault will spread and unbalance the rest of it, which could lead to voltage spikes, which may well take out your PC. Note that as this is a quality brand, the protection circuits in it are likely to save you, but don't rely on them.


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## Widjaja (Jul 28, 2011)

Something is not replenishing charge in your PSU from the sounds of things.
Most likely failing capacitors.

Since it is only getting worse then eventually your system is going to fail.

I personally thought the rail supplying  3.3v was directly to RAM.


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## qu4k3r (Jul 28, 2011)

Thanks for your answers.

I'll try to find the invoice in order to do rma,
anyways I think I'll buy a new one, may be more powerfull.-


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## p_o_s_pc (Jul 28, 2011)

qu4k3r said:


> Thanks for your answers.
> 
> I'll try to find the invoice in order to do rma,
> anyways I think I'll buy a new one, may be more powerfull.-



if you can get it replaced but still want something else you could always sell it. People are crazy about that brand of PSUs so selling it shouldn't be hard at all.


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## qu4k3r (Jul 28, 2011)

p_o_s_pc said:


> if you can get it replaced but still want something else you could always sell it. People are crazy about that brand of PSUs so selling it shouldn't be hard at all.



How much could I ask for it the way it is?


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## p_o_s_pc (Jul 28, 2011)

qu4k3r said:


> How much could I ask for it the way it is?



I dont know that anyone would even pay for a defective PSU unless they had a way to get it replaced or has 1337 skillz and can repair them. maybe $20 shipped


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## Widjaja (Jul 29, 2011)

I agree $20 max.
There are people out there who can repair PSUs and have the spare parts to do so.

Out the back of where I work we have dozens of PSUs for machines which had been removed from machines.


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## qu4k3r (Jul 29, 2011)

Readings went back to normal:

3.248~3.264v idle
3.216~3.232v full load


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## Frick (Jul 29, 2011)

The reading could be wrong too. My +12V line is apparently running at 9V, so always take software/bios voltage readings with a grain of salt.

You really need a multimeter or better yet an oscilliscope to see how it really does.


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## qubit (Jul 29, 2011)

qu4k3r said:


> Readings went back to normal:
> 
> 3.248~3.264v idle
> 3.216~3.232v full load



It just means the PSU is intermittent. It's still faulty.


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## Widjaja (Jul 30, 2011)

I can say I have come across system boards which drained PSUs, but to the point where the the machine would not work.
I don't think it's the case here.
If you are going to just buy another PSU, I suppose you could try out this power supply in another machine when you have the chance and see if the drain is the same.


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## newtekie1 (Jul 30, 2011)

qu4k3r said:


> All voltage reading were made with Everest (don't have a multimeter) and they match idle reading in bios.



I wouldn't do anything until I confirmed these readings with a multimeter.  Even a cheap one from Harbor Freight would give more accurate reading than the sensors on the motherboard.


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