+12V: how much is not enough?

[RobertMcDonald]

Simple question: on a power supply, what is the minimum voltage the +12V should be at to avoid damaging components?

Thanks!

 

[jonnyGURU]

You don't "damage components" with low 12V. It's high 12V that does the damage. I'd rather have a 12V at 11.8 than a 12V at 12.2.

But to answer your question: +/- 5% is the standard. So 11.4 to 12.6 is "acceptable."

 

[mechBgon]

And check it with a real voltage-measuring instrument of some kind. http://www.fluke.com

 

[RobertMcDonald]

Originally posted by: jonnyGURU
You don't "damage components" with low 12V. It's high 12V that does the damage.

Low voltage doesn't break things? I was told in physics way back in high school that lower voltage made the amperage go up which resulted in higher circuit friction and thus heat, burning out components.

 

[deathwalker]

The basic rule of thumb is 5% +/-....I prefer 3%. Rail stability is just as or more important than basic voltage reading. Also hold no faith in the voltage readings you get from the bios. Get a digital multimeter and read the voltage in operation. BTW..JonnyGuru's opinions on Power supplies are widely accepted as very good on AT, you would be well advised to consider his thoughts.

 

[jonnyGURU]

Originally posted by: RobertMcDonald

Originally posted by: jonnyGURU
You don't "damage components" with low 12V. It's high 12V that does the damage.

Low voltage doesn't break things? I was told in physics way back in high school that lower voltage made the amperage go up which resulted in higher circuit friction and thus heat, burning out components.

As a rule, that is true simply due to the math required to obtain watts: A1 * V1 = W1, W2 / V2 = A2. If W1 = W2 and V1 < V2, then A2 would have to be > A1.

But -/+ 5% voltage is well within operating tolerance of the component. The .6V deviation isn't going to cause a significant fluctuation in amperage to cause a problem. Typically, the amperage is the constant, the voltage is the variable and thus the wattage is variable.

I find if voltages are too low, components don't just "suck more amperage to compensate" they just cease to work.

For example: High end video card, same power supply, 12V at 12.2V works fine. 12V at 12.6V works, but runs hotter. 12V drops to 11.5V, PC locks up.

 

[RobertMcDonald]

Originally posted by: jonnyGURU
For example: High end video card, same power supply, 12V at 12.2V works fine. 12V at 12.6V works, but runs hotter. 12V drops to 11.5V, PC locks up.

Like this?

My power supply has been running at 11.52V (according to ASUS Probe and my BIOS) and I'm wondering if it has something to do with my system sucking for the past... ten months.

 

[mechBgon]

Originally posted by: RobertMcDonald

Originally posted by: jonnyGURU
For example: High end video card, same power supply, 12V at 12.2V works fine. 12V at 12.6V works, but runs hotter. 12V drops to 11.5V, PC locks up.

Like this?

My power supply has been running at 11.52V (according to ASUS Probe and my BIOS) and I'm wondering if it has something to do with my system sucking for the past... ten months.

Now do a reality check with a multimeter.