Molex connector voltage tolerances

[Dougie]

Hi;

I was wondering if anyone knows what the +12 and +5 volt measurements should be under no load and also under load? One would think that under no load ( nothing connected ) the voltages should be slightly higher than 12 volts or 5 volts.

Thanks;

Dougie

[Serunson]

Well for the microchips inside your computer, they can withstand up to +/- 5V. The 12V line is for the other components (fans etc). No load implies 0V in the elctronics world, if nothing was connected to take the current away (to be precise it is actually giving out the current) it would be a 'floating input' which means that the circuit will not work. So no load voltage would actually be 0V or a negative voltage line.
Hope that helps ya.

[Chaky]

I think that 12V and 5V should not be higher than declared on the PSU. If they were, it would represent a danger for the peripherals. I've heard that the measuring volts by BIOS is very inaccurate. I have ASUS mobo and my ASUS PC Probe reports, and sometime alerts of 12V going too low (-10%), but after I press the sleep button, and awake it just after everything stops spinning, 12V line comes back to "normal" 11.9V. If I repeat the sleep-awake cycle, it drops below 11V and alert goes off again. Like a clock-work. No changes with the drives that are powered with molex..
I doubt that the readings are accurate at all.

BTW, in a electronics world, if you measure the voltage, than the voltmeter closes the circuit and, therefor, it measures the volts for almost-no-load-at-all state.

[Dougie]

Thank you CHAKY!! I have a Fluke digital multimeter with a very high input impedance, approx 10 megaohms and should put little if any load on what it's measuring, so what you see is what you get LOL!!

I spent a lot on my new computer but bought a cheaper PSU. Its is a 500 watt MIOS, made in Canada. I also know that you can spend twice or triple the price I payed for my PSU on other brands with the same wattage. I think I will measure my PSU's voltages when the computer is powered up this weekend to see if the voltages are up to what they should be under full load.

Dougie

[Chaky]

The wattage you see declared is the power output, so buying $50 PSU or $150 PSU that gives 500W of power shouldn't make any difference with the PC in a short run. In a long run, you can expect that the cheap one won't last as long as the pricier one, for the difference of materials used. Price difference can also be because of over-voltage protection and such extras that are not free.