*resolved*How do I test voltages with a multimeter?

[PorBleemo]

I have a Fortron 350w Aurora. I am very happy with it but the +5VSB rail is almost 10% off. Everything else (according to the BIOS anyway) is within 5%. Can anyone tell me if this is a crucial rail to keep on mark?

And if it is failing, I'm looking at the new Fortron Blue Storm series. Mainly because I still want a large fan to help exhaust air from the CPU. As usual I want the rails to be very stable.

It shouldn't be too loud (but I think the Aurora is quiet ). Thanks!

-Por

[Callous]

You cannot just read the voltages in software and say the rails are off.

My enermax in windows says the +5v is hovering 4.68, when in fact using a digital multimeter worst case scenario it's at 4.98, and that's measured from the lead coming from the video card.

Use a multimeter before you unnecesarrily spend money on another PSU.

If your system's stable, why worry?

[PorBleemo]

Thanks for the suggestion. I think I'll go someplace locally to pick up one of these devices. Do I need a multimeter to measure all the rails?

[Callous]

A *digital* multimeter will measure your +5 and +12. I dont think there is a way to measure your +3.3 or -12 rails.

[PorBleemo]

A *digital* multimeter will measure your +5 and +12. I dont think there is a way to measure your +3.3 or -12 rails.

That's alright. The -12v rail means nothing to me and if I wanted to measure the 3.3v I would probably have to insert the taps into the 20-pin ATX connector and jump the PSU.

[Skylined]

The -12V and -5V are just grounds.
You can test all the voltages, 12V, 5V and 3.3V with a digital multimeter.

[PorBleemo]

The -12V and -5V are just grounds.
You can test all the voltages, 12V, 5V and 3.3V with a digital multimeter.

Is my method of testing the 3.3v rail correct then? Thanks!

[mathias]

A *digital* multimeter will measure your +5 and +12. I dont think there is a way to measure your +3.3 or -12 rails.

That's alright. The -12v rail means nothing to me and if I wanted to measure the 3.3v I would probably have to insert the taps into the 20-pin ATX connector and jump the PSU.

But that'll only tell you what it is with the PSU idle(which many aren't ever supposed to be anyway), not under the load of your PC. If you want to test the 3.3 volt rail, I think mondularizing the 6 pin connector would probably be a good idea.

The -12V and -5V are just grounds.

No, you can for example connect a fan to the +5 and -5 rails for 10 volts.

[PorBleemo]

A *digital* multimeter will measure your +5 and +12. I dont think there is a way to measure your +3.3 or -12 rails.

That's alright. The -12v rail means nothing to me and if I wanted to measure the 3.3v I would probably have to insert the taps into the 20-pin ATX connector and jump the PSU.

But that'll only tell you what it is with the PSU idle(which many aren't ever supposed to be anyway), not under the load of your PC. If you want to test the 3.3 volt rail, I think mondularizing the 6 pin connector would probably be a good idea.

The -12V and -5V are just grounds.
You can test all the voltages, 12V, 5V and 3.3V with a digital multimeter.

No, you can for example connect a fan to the +5 and -5 rails for 10 volts.

How exactly does one "mondularizing the 6 pin connector"? And I don't have a six pin connector in my system, either four pins or twenty.

[sthayashi]

Any built-in SATA connectors?

[lenny]

The -12V and -5V are just grounds.
You can test all the voltages, 12V, 5V and 3.3V with a digital multimeter.

Is my method of testing the 3.3v rail correct then? Thanks!

Yes, that is one way of doing it. Some PSUs come with a 6 pin aux connector. The orange wires are 3.3V. You can measure from there as well.

I don't quite understand the "-12V and -5V are just grounds" comment. ATX 2.0 spec does not require -5V, but isn't -12V still there?

Whether it is a digital or analog multimeter it'll be able to measure voltage. Be wary of cheap multimeters. It may be even less accurate than your motherboard's sensors.

Finally, regarding 5VSB, thats the 5V standby that the PSU provides the motherboard when the system is off. It is used for powering up various parts of your system, and is required for tasks such as retaining the CMOS config / powering the RTC without draining the battery, providing power to some USB devices if so configed in BIOS, powering the keyboard, and other devices such as NIC (wake on lan) and serial port (wake on ring). It is also used to refresh the RAM in S3 (suspend to RAM) state.

If your system wakes up from sleep / standby and can power up from soft off without any problem, in all ways that you use (power button, keyboard, mouse click, etc) then there is nothing to worry about. Be aware that problems with waking up from S3 is usually due to faulty drivers.

Edit : took too long writing this. Since you don't have the 6 pin aux, as sthayashi pointed out, the SATA also has 3.3V (4 pin molex to SATA converters don't count).

If you're feeling *really* adventurous, open up the PSU and tap the voltage lines from the PCB directly. But I'd really advise against it. One wrong move and *poof* fried PSU, fried motherboard, and possibly a heart that's no longer beating.

I'm not sure if there are ATX20 splitters available. That will be the safer route to take.

Personally, I'd just do what I said earlier about powering up / waking up the system.

[mathias]

How exactly does one "mondularizing the 6 pin connector"? And I don't have a six pin connector in my system, either four pins or twenty.

Cut of most of the 6 pin connector wires from the PSU, attach 2 molex connectors or some other connector(s) to matching bare wires at both ends. With molex connectors, I would recomend making 5volt and 3.3 volt adapters for fans, just be careful never to accidentally connect something other than a fan to them.

[PorBleemo]

The -12V and -5V are just grounds.
You can test all the voltages, 12V, 5V and 3.3V with a digital multimeter.

Is my method of testing the 3.3v rail correct then? Thanks!

Yes, that is one way of doing it. Some PSUs come with a 6 pin aux connector. The orange wires are 3.3V. You can measure from there as well.

I don't quite understand the "-12V and -5V are just grounds" comment. ATX 2.0 spec does not require -5V, but isn't -12V still there?

Whether it is a digital or analog multimeter it'll be able to measure voltage. Be wary of cheap multimeters. It may be even less accurate than your motherboard's sensors.

Finally, regarding 5VSB, thats the 5V standby that the PSU provides the motherboard when the system is off. It is used for powering up various parts of your system, and is required for tasks such as retaining the CMOS config / powering the RTC without draining the battery, providing power to some USB devices if so configed in BIOS, powering the keyboard, and other devices such as NIC (wake on lan) and serial port (wake on ring). It is also used to refresh the RAM in S3 (suspend to RAM) state.

If your system wakes up from sleep / standby and can power up from soft off without any problem, in all ways that you use (power button, keyboard, mouse click, etc) then there is nothing to worry about. Be aware that problems with waking up from S3 is usually due to faulty drivers.

Edit : took too long writing this. Since you don't have the 6 pin aux, as sthayashi pointed out, the SATA also has 3.3V (4 pin molex to SATA converters don't count).

If you're feeling *really* adventurous, open up the PSU and tap the voltage lines from the PCB directly. But I'd really advise against it. One wrong move and *poof* fried PSU, fried motherboard, and possibly a heart that's no longer beating.

I'm not sure if there are ATX20 splitters available. That will be the safer route to take.

Personally, I'd just do what I said earlier about powering up / waking up the system.

Thanks for the advice. I bought a Craftsman Multimeter from Sears and I'll try to use the small pins on the SATA connector.

Thanks for the help everyone!

-Por