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Digital Multitester capable of testing more than 10A of current?

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Ok. I think I've got it. I grabbed the spare 9007 Halogen for my wife's 2002 Jetta. 😀

At first I thought I finally fried my Antec because my tester was saying I was only getting +5VSB!, but it turns out that I was just overloading the 5V by wiring up the low AND high beams on the 9007.

I hooked the Ultra back up and the high beam lit up, but as soon as I plugged in the distribution block, even without turning any of the lights on, the PSU's overload protection kicked in and the tester was back to saying I was only getting +5VSB.

I disconnected the high beam and tried it again and the PSU stayed up and running. I clicked on all four bulbs and where I was getting 11.27, I'm now getting 11.5 which is still within spec. One more bulb and I'll still be within the PSU's spec if the voltage stays above 11.4.

So any idea why this works this way? Kind of weird. "Let's put more of a load on the 5V and this will give us more voltage on the 12V!" Crazy stuff. 🙂
 
Originally posted by: sharkeeper
Also computer mainboards tend to consume power in a non-linear fashion!
Click to expand...

Well sure, but I'm looking to load a PSU in a measurable worst case scenario. Not just a pass/fail manner.
 
Even the Powmax works now that there's a load on the 5V. All four bulbs will light up now, but it's pathetic. The 12V drops down to 11.3V with only 7A load. Ugg!
 
It has to do with the way switching power supplies work.. I don't really know much about it, but I know that you need to load the 5v rail for everything to function properly.

Basically, there is a minimum amperage rating for some rails, and it isn't 0. They're "independant", but still tied in together somehow... or something.
 
Here's an interesting article.

Most of the power supplies in use today do not require as much of a load as the original IBM AT power supply. In most cases, a minimum load of 0?0.3 amps at +3.3v, 2.0?4.0 amps at +5v, and 0.5?1.0 amps at +12v is considered acceptable. Most motherboards easily draw the minimum +5v current by themselves. The standard power supply cooling fan draws only 0.1?0.25 amps, so the +12v minimum load might still be a problem for a diskless workstation. Generally, the higher the rating on the supply, the more minimum load required; however, exceptions do exist, so this is a specification you want to check when evaluating power supplies.
Click to expand...

It sounds like you need to load ALL the rails.. Basically simulate a computer... to reliably test them.....

That explains your strange readings.
 
Originally posted by: Eli
Here's an interesting article.

Most of the power supplies in use today do not require as much of a load as the original IBM AT power supply. In most cases, a minimum load of 0?0.3 amps at +3.3v, 2.0?4.0 amps at +5v, and 0.5?1.0 amps at +12v is considered acceptable. Most motherboards easily draw the minimum +5v current by themselves. The standard power supply cooling fan draws only 0.1?0.25 amps, so the +12v minimum load might still be a problem for a diskless workstation. Generally, the higher the rating on the supply, the more minimum load required; however, exceptions do exist, so this is a specification you want to check when evaluating power supplies.
Click to expand...

It sounds like you need to load ALL the rails.. Basically simulate a computer... to reliably test them.....

That explains your strange readings.
Click to expand...

Good read. You know what's funny, though.... In all my years, I've yet to put a load on a power supply when I've tested it for Power On with a mere paper clip. I have yet to have one blow up because of it, or simply shut itself down. This tells me that MOST ATX power supplies actually DO have load resistors built into them.

I'm not sure if I need a 3.3V load or not. I think the little tester that I use to keep the PSU's fired up (I retired the paper clip) might keep enough load on it to suffice, but I will install at least one more light bulb in the center of the board that will always be hooked up to 5V. At the very least, I can say it's the "test bench on" light. Maybe I'll get an amber bulb for that! 🙂

 
colt45 owns you 😉

I forget the technical reason why you need a load on the other rails for it to work right.. it's been a while since i've looked at a SMPS schematic !
Good to hear it is working better for you.
 
Originally posted by: Colt45
colt45 owns you 😉

I forget the technical reason why you need a load on the other rails for it to work right.. it's been a while since i've looked at a SMPS schematic !
Good to hear it is working better for you.
Click to expand...

Read the link in Eli's post. It explains it quite well.


 
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