Test Power Supply Under Load
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glricht
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From my experience, the only thing a multi-meter can do is to tell you that the PSU is toast. It can't tell you if the PSU is good because conditions change when it's under load. If I suspect that a problem may be PSU-related, I just swap it out for a known good unit and see if that resolves the problem.
Encrypted Existence
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This here^, only definitive way of knowing is to swap for known good. Same goes for RAM.
cypress
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I still have a PSU tester in my bag that I carry with me. But I rather swap it out with a known good one, which I always have one in stock.
NviGate Systems
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PSU Tester can tell you if it's dead or over/undervolt but can't put a load on.
Now, you can get loads to place on unit and monitor with a PSU Tester. But it need to be a large load, much easier to swap units.
Now, you can get loads to place on unit and monitor with a PSU Tester. But it need to be a large load, much easier to swap units.
glennd
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Is there such a thing as a PSU load tester? The testers everyone is talking about here just measure the voltage but not under load. What you really want is a tool that can put the PSU under load and then measure the voltage.
NviGate Systems
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I'm sure the ODM's have them, they must put a min/max load when tested for QC.
You can get ceramic loads of various amounts rated for certian wattage. You would have to wire up a pass through adapter to pull a load then go to the tester. For someone that like to tinker it should be fairly simple.
http://www.tomshardware.com/reviews/how-we-test-psu,4042.html#p2
Just found that
You can get ceramic loads of various amounts rated for certian wattage. You would have to wire up a pass through adapter to pull a load then go to the tester. For someone that like to tinker it should be fairly simple.
http://www.tomshardware.com/reviews/how-we-test-psu,4042.html#p2
Just found that
Porthos
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Same here.
brandonkick
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I'm not every electronically inclined to this level, but I'd imagine you could build something to draw certain thresholds of power out of the power supply. I'm not sure you'd want to though. A failing / faulty power supply could start barfing fire balls at you. I'd rather just swap out with a new power supply to check, and avoid burning the place down.
Multi meter is a good "is it already dead" check, but as you know, you can get good enough non load readings and have that not mean a darn thing.
Just swap it out with a new power supply.
Multi meter is a good "is it already dead" check, but as you know, you can get good enough non load readings and have that not mean a darn thing.
Just swap it out with a new power supply.
GTP
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I heard this somewhere on the forum, which is good advice...
"If in doubt, just swap it out!"
"If in doubt, just swap it out!"
Mainstay
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Agreed all. And thank you for the responses. I was just double checking that I wasn't missing some awesome new tester / method.
Yup - for PS's and HD's.
Yup - for PS's and HD's.
glennd
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I also saw someone say, "If it ain't broke, fix it 'til it is"
Dave R Mason
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You could rig up a power supply harness connector with power resistors...
..
ust remember you also have two wires that must be dealt with to turn the PS on. These are the Sense,and power leads. The sense must be energized to energize the power supply, and keep it inlet lead only needs momentary action to start the power supply.
...
that said::::
...
Ohms law applies here:
E(Voltage) is equal to I (current) multiplied by R ( Resistance).
..
So a 5 volt supply under 1 amp load would require a 5.0 ohm power resistor.
But now you have to factor in the power rating.
..
New formula:
Power (in watts) is determined by I (current) multiplied by E (voltage).
..
So your 5Volt Supply loaded by the 5Ohm resistor drawing 1 Amp will need to dissipate 5 watts.
..
In reality I would use at least a 12-watt power resistor ( at the minimum - mainly because it is over twice the required rating - the other factor is unless you are planning on grilling on the resistor, you want to up size the rating)
....
Digital Volt Ohm Meters (VOMs) Do not measure voltage under load. They are a bridged measurement devices. You have to provide the load.
...
If you are serious about testing PC power supplies build two test harnesses, one with only a PC receptacle (you only need a 24-Pin receptacle - sinJce the fundamental difference between 20-Pin and 24-Pin is the additional 12-Volt rail.
..
The second harness would basically be like one of those ATX Power Supply Extender Harnesses. You just need to provide tip jacks to plug the DVOM probes into to measure the different voltages.
...
I actually have two of these, because I actually do motherboard repairs and need to see what the power rails are doing.
...
The main one has a male and female connector - basically an extended with tip pin jacks installed to hook up a DVOM across the various voltage rails with the PS hooked up and powering Test Motherboard.
..
The second one is basically the same, but I'd a she with one PS receptacle that feeds two motherboard plugs. This allows me to hook up one of the ATX PS testers. This one I use to troubleshoot Motherboards that kill Power supplies. This harness ha s 10-Ohm 40-watt power resistors on the 5-Volt, and 3-Volt power rails ( and yes the minus and plus 5-Volt rails). I use 15-ohm 40-Watt resistors in-store on the 12-Volt rails.
...
note: Modern complex PC Power supplies have multiple Voltage Supply Rails.
You need to load/isolate all the voltage rails to get accurate test results.
...
you cannot use the load test resistors with the in-store isolation resistors and test voltages just anywhere in the harness. The load resistors illiteracy with the motherboard when the motherboard us plugged in and loading the power supply. To get an accurate measurement using a test harness with load resistors hooked up and powering a motherboard changes the dynamics. This is beyond the tech level of this discussion.
..
this is just a simple explanation of how to build a dynamic power supply load test harness.
....
hope this helps
..
ust remember you also have two wires that must be dealt with to turn the PS on. These are the Sense,and power leads. The sense must be energized to energize the power supply, and keep it inlet lead only needs momentary action to start the power supply.
...
that said::::
...
Ohms law applies here:
E(Voltage) is equal to I (current) multiplied by R ( Resistance).
..
So a 5 volt supply under 1 amp load would require a 5.0 ohm power resistor.
But now you have to factor in the power rating.
..
New formula:
Power (in watts) is determined by I (current) multiplied by E (voltage).
..
So your 5Volt Supply loaded by the 5Ohm resistor drawing 1 Amp will need to dissipate 5 watts.
..
In reality I would use at least a 12-watt power resistor ( at the minimum - mainly because it is over twice the required rating - the other factor is unless you are planning on grilling on the resistor, you want to up size the rating)
....
Digital Volt Ohm Meters (VOMs) Do not measure voltage under load. They are a bridged measurement devices. You have to provide the load.
...
If you are serious about testing PC power supplies build two test harnesses, one with only a PC receptacle (you only need a 24-Pin receptacle - sinJce the fundamental difference between 20-Pin and 24-Pin is the additional 12-Volt rail.
..
The second harness would basically be like one of those ATX Power Supply Extender Harnesses. You just need to provide tip jacks to plug the DVOM probes into to measure the different voltages.
...
I actually have two of these, because I actually do motherboard repairs and need to see what the power rails are doing.
...
The main one has a male and female connector - basically an extended with tip pin jacks installed to hook up a DVOM across the various voltage rails with the PS hooked up and powering Test Motherboard.
..
The second one is basically the same, but I'd a she with one PS receptacle that feeds two motherboard plugs. This allows me to hook up one of the ATX PS testers. This one I use to troubleshoot Motherboards that kill Power supplies. This harness ha s 10-Ohm 40-watt power resistors on the 5-Volt, and 3-Volt power rails ( and yes the minus and plus 5-Volt rails). I use 15-ohm 40-Watt resistors in-store on the 12-Volt rails.
...
note: Modern complex PC Power supplies have multiple Voltage Supply Rails.
You need to load/isolate all the voltage rails to get accurate test results.
...
you cannot use the load test resistors with the in-store isolation resistors and test voltages just anywhere in the harness. The load resistors illiteracy with the motherboard when the motherboard us plugged in and loading the power supply. To get an accurate measurement using a test harness with load resistors hooked up and powering a motherboard changes the dynamics. This is beyond the tech level of this discussion.
..
this is just a simple explanation of how to build a dynamic power supply load test harness.
....
hope this helps
Dave R Mason
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Have one of those - seldom actually use it.
Where did you get yours?
Where did you get yours?
GTP
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And after all that time, money and fiddling about you could have just swapped out the PSU and moved on...just my .02
X11, swap it to be 100% sure even when the voltages are present and within spec. The tolerance is +/- 5% for all positive voltages and +/- 10% for the negative 12V.
To test it I own a true RMS-DVM but in this case a cheapo digital unit will suffice to measure voltage. I use an old mobo with a CPU chip and RAM installed and two HDDs secured and connected to each other with electrical tape to keep it neat and easy to use.
Just plug the suspect PSU into the mobo and read the voltages with the DVM. The mobo/RAM/CPU loads the 5V rails and the HDD's load both the 5V and 12V rails.
To test it I own a true RMS-DVM but in this case a cheapo digital unit will suffice to measure voltage. I use an old mobo with a CPU chip and RAM installed and two HDDs secured and connected to each other with electrical tape to keep it neat and easy to use.
Just plug the suspect PSU into the mobo and read the voltages with the DVM. The mobo/RAM/CPU loads the 5V rails and the HDD's load both the 5V and 12V rails.
Your PCMD
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