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(help) not enough power on 12v rail?

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December 6, 2006 6:24:19 PM

I have a compaq presario sr1030nx computer with a thermaltake 430watt tr2 power supply. i had to upgrade the stock 250watt power supply upon installing a graphics card(gf4 mx440). i have checked the voltages in everest home edition and it reads 11.07-11.19volts on the 12volt rail i then checked using a multimeter and got similar results. seems way too low for a 430watt ps so i take out my power supply from my other computer to see if it could power it(silverstone zeus 520watt) and the voltage is nearly the same on the 12v. for the past few months i have noticed the hd has gotten very loud and has failed smart tests for spin up rate i am thinking that this is due to low 12v readings.

i was wondering if anyone has ANY ideas about what is causing this. i seem to think it is the motherboard but if i replace it i lose the recovery option and will have to buy windows xp as well so i hope there might be another solution.

More about : power 12v rail

December 6, 2006 8:34:43 PM

That does seem a bit low (assuming 12v +/- 3%), but keep in mind the watt rating of the power supply has no bearing on the voltage. A 150W power supply should supply the same voltage as a 600W supply. Now, the amps supplied will vary, but voltages should be pretty much equal.

That said, if two power supplies exhibit the same behavior, you may want to check the input voltages (i.e. your power outlet on the wall). I do not see a motherboard causing the problems you describe. Calculating the rating is going to tell you watts and amps, not volts. Volts are assumed to be within a given range.
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December 6, 2006 11:05:13 PM

thanks for the replies and about the voltage issue the stress on a power supply from power hungry components will affect the voltage. The tolerance level is actually 12v +/- 5% on my power supply but it still seems a little too low. The outlets are not causing the problems as I just had them tested last week thinking the exact problem. I still have no idea as to why the silverstone ps will not power it either. the exact 12v voltage with silverstone is 11.17-11.23v

I used the wattage calculator and according to that my computer should use 239watts

specs are as follows:
-asus a7v8x-la oem compaq
-amd 3000+(2.16ghz)
-768mb ddr400
-160gb maxtor
-hp dvd-rw and cd-rom+floppy
-thermaltake 430w tr2
-msi geforce 4 mx440 oc bios mod
-thermaltake smart 80mm fan
-sound blaster live 5.1
-new case due to very poor compaq case cooling
December 7, 2006 1:02:50 AM

Quote:
thanks for the replies and about the voltage issue the stress on a power supply from power hungry components will affect the voltage.


No, it does not affect the voltage. It increases current on the rail, but the voltage is not affected. Explain how you think more components affect voltage. This is equivalent of saying that the more items you plug into your outlets at home, the more the voltage will drop below 110V. It doesn't work that way.

Quote:
The tolerance level is actually 12v +/- 5% on my power supply but it still seems a little too low.


Seems? Do the math:

12 * .05 = 0.6

So the voltage should fall between 11.4 and 12.6 volts. So, yes, indeed, the voltage is not within spec.

Quote:
The outlets are not causing the problems as I just had them tested last week thinking the exact problem. I still have no idea as to why the silverstone ps will not power it either. the exact 12v voltage with silverstone is 11.17-11.23v


Tested as in how? You can do checks to see if it is wired correctly, how many volts are supplied, how many amps the circuit can handle, etc. Specifically, what did you test?

Quote:
I used the wattage calculator and according to that my computer should use 239watts

specs are as follows:
-asus a7v8x-la oem compaq
-amd 3000+(2.16ghz)
-768mb ddr400
-160gb maxtor
-hp dvd-rw and cd-rom+floppy
-thermaltake 430w tr2
-msi geforce 4 mx440 oc bios mod
-thermaltake smart 80mm fan
-sound blaster live 5.1
-new case due to very poor compaq case cooling


Again, forget watts; they have no impact on voltage. The only variable you have in your system is amps, and increased amps is usually caused by more system components. Voltage should remain fairly constant, so given the equation:

P = I * E (Watts = Amps * Volts)

More amps = more watts.
December 7, 2006 1:30:03 AM

There's NO WAY you had to replace the PSU when you installed the MX440 graphics card. That thing draws like NO POWER AT ALL.

So do yourself a favour and put the old PSU back in there.

I swear, people are really fucked up when it comes to picking PSU. Jebus H Chribt on a pony, most people are sitting on 450Watt+ PSU on a PC that will NEVER draw more than 225 watts.

It's just stupid.
December 7, 2006 2:19:21 AM

I second the motion to install the original PSU. Like Mobius said, the Geforce4 MX440 consumes next to nothing.

In my Dell Dimension 4500 I've been running the following since July:

Asrock 775i65G mobo
Pentium D 805 @1.15 volts, 2.66GHz w/stock hsf
2x256MB DDR ram
Turtle Beach sound card from 1998
Winfast TV2000 XP Expert video capture card
Geforce3 Ti200
92mm exhaust fan
80Gb Seagate Baracuda IV hdd
200GB Seagate Baracuda 7200.7 hdd
12x DVD-ROM drive
16X DVD-RW drive
3 1/2" floppy

All this on the original 250 watt power supply, which will turn 5 years old this spring. Your original Compaq psu should be more than adaquate for your configuration.

EDIT: I just tried Extreme PSU's latest calculator, and it suggests I should be using a 300 watt psu for the above hardware (odd, last version of extreme PSU said 253 watts for the same configuration). You'll be fine with your 250 watt Compaq PSU.
December 7, 2006 9:53:26 AM

the voltage and wiring were tested by an electrician and both are good. the outlet also supports my other computer (dual core with that silverstone) just fine. lets get something straight here i did NOT upgrade the power supply just because i added mx440 i had the original compaq power supply and it fell just below 11v on the 12v rail. i dont know why but i can assure u that the three different power supplies all give out diff voltage on the 12v rail on my computer. all other voltages are completly perfect(3.3v,5v) its just the 12v that is screwed up. i have also tried a gfi outlet in the basement (direct connection) and i still get the same 12v power.

I have no idea why this is i was just asking for suggestions
December 7, 2006 11:06:10 AM

Quote:
the voltage and wiring were tested by an electrician and both are good. the outlet also supports my other computer (dual core with that silverstone) just fine. lets get something straight here i did NOT upgrade the power supply just because i added mx440 i had the original compaq power supply and it fell just below 11v on the 12v rail. i dont know why but i can assure u that the three different power supplies all give out diff voltage on the 12v rail on my computer. all other voltages are completly perfect(3.3v,5v) its just the 12v that is screwed up. i have also tried a gfi outlet in the basement (direct connection) and i still get the same 12v power.

I have no idea why this is i was just asking for suggestions


Understood, but upgrading a power supply has no affect on voltage. I recommend reading up a bit of electrical theory before jumping to conclusions like that. I just don't want you to believe that more components = less voltage.

It could be a bad ground within the case or even a bad power cord.
December 7, 2006 1:59:18 PM

Quote:
There's NO WAY you had to replace the PSU when you installed the MX440 graphics card. That thing draws like NO POWER AT ALL.

So do yourself a favour and put the old PSU back in there.

I swear, people are really ****** up when it comes to picking PSU. Jebus H Chribt on a pony, most people are sitting on 450Watt+ PSU on a PC that will NEVER draw more than 225 watts.

It's just stupid.


What makes the difference anyway? Do you use your PSU to its full capacity? My guess is no, so is that a dumb idea too? Having enough power doesn't mean having just enough. I always prefer to have a bit extra for when an upgrade is needed.
December 7, 2006 5:58:08 PM

well i took your advice and tried a new power cord and it makes no difference :evil:  . as i am sure u know the ground wire to the psu is screwed to the psu case and is in turn transfered to the computer case just like every psu. the ground wire and case connection is good so it is not a ground issue. plus if the psu was not grounded properly the voltage in the capacitators would be too high and it would short out.

does anyone have any more suggestions[/b]
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