How do I check if power supply for my PC is working? Heeeeeeeeelp!!!

Hello, I am trying to build a new PC. After connecting all the parts,
I turned the switch on and... nothing.
I suspect that the power supply is not working, or the circuit on the
motherboard that switches the power supply on is not working.
When I flip the switch on the back of the power supply on, the
keyboard LED turns on for a second. However, when I press the major
switch, nothing happens. No fans move, and there are no noises. I
checked the major switch with an ohmmeter, and the switch seems like
it works.
I'm not sure if the power supply or the motherboard circuit that
starts the power supply isn't working.
So my question is, how can I check if the power supply is working?
Thank you very much

Zalek

zalek wrote:
> Hello, I am trying to build a new PC. After connecting all the parts,
> I turned the switch on and... nothing.
> I suspect that the power supply is not working, or the circuit on the
> motherboard that switches the power supply on is not working.
> When I flip the switch on the back of the power supply on, the
> keyboard LED turns on for a second. However, when I press the major
> switch, nothing happens. No fans move, and there are no noises. I
> checked the major switch with an ohmmeter, and the switch seems like
> it works.
> I'm not sure if the power supply or the motherboard circuit that
> starts the power supply isn't working.
> So my question is, how can I check if the power supply is working?
> Thank you very much
>
> Zalek

There is a power supply spec here, so you can see the signal names.

http://www.formfactors.org/developer...public_br2.pdf

To start with, the power supply is split into two pieces. The +5VSB
output, is available as soon as the rear switch is turned on. The +5VSB,
in turn, flows down the main power cable and powers some motherboard
logic.

The second half of the power supply, operates the 3.3V/5V/12V/-12V
outputs. The power is "soft switched" by means of the logic level
on the PS_ON# signal. The PS_ON# signal normally is pulled to +5V,
by an internal resistor. To start the supply, PS_ON# needs to be
grounded (zero volt level).

Inside the computer, the chain of command looks like this.

Front Motherboard Grounds Main To main ATX
Power ------------ Logic runs ----- PS_ON# --------------- part of supply,
Switch on +5VSB to operate Cable fans start to spin
(momentary (latches when PS_ON# is
contact) signal) grounded

An ATX supply can be operated on the test bench.

1) Connect a dummy load to the supply. You could use a couple old
hard drives, and connect them to the Molex connectors. I have
a home made load box that I use.

2) Switch on power supply at the back.

3) Connect Green to Black with a paper clip. The fans should spin.

Then, you can use a multimeter to measure the voltages if you want.
I use a load box, drawing a light load (<100W), to help ensure
that the power supply will be regulating properly when I measure
it. I actually test new power supplies, before I use them.

Paul

On Jun 19, 10:57 pm, Paul <nos...@needed.com> wrote:
> zalek wrote:
> > Hello, I am trying to build a new PC. After connecting all the parts,
> > I turned the switch on and... nothing.
> > I suspect that the power supply is not working, or the circuit on the
> > motherboard that switches the power supply on is not working.
> > When I flip the switch on the back of the power supply on, the
> > keyboard LED turns on for a second. However, when I press the major
> > switch, nothing happens. No fans move, and there are no noises. I
> > checked the major switch with an ohmmeter, and the switch seems like
> > it works.
> > I'm not sure if the power supply or the motherboard circuit that
> > starts the power supply isn't working.
> > So my question is, how can I check if the power supply is working?
> > Thank you very much
>
> > Zalek
>
> There is a power supply spec here, so you can see the signal names.
>
> http://www.formfactors.org/developer...2_2_public_br2...
>
> To start with, the power supply is split into two pieces. The +5VSB
> output, is available as soon as the rear switch is turned on. The +5VSB,
> in turn, flows down the main power cable and powers some motherboard
> logic.
>
> The second half of the power supply, operates the 3.3V/5V/12V/-12V
> outputs. The power is "soft switched" by means of the logic level
> on the PS_ON# signal. The PS_ON# signal normally is pulled to +5V,
> by an internal resistor. To start the supply, PS_ON# needs to be
> grounded (zero volt level).
>
> Inside the computer, the chain of command looks like this.
>
> Front Motherboard Grounds Main To main ATX
> Power ------------ Logic runs ----- PS_ON# --------------- part of supply,
> Switch on +5VSB to operate Cable fans start to spin
> (momentary (latches when PS_ON# is
> contact) signal) grounded
>
> An ATX supply can be operated on the test bench.
>
> 1) Connect a dummy load to the supply. You could use a couple old
> hard drives, and connect them to the Molex connectors. I have
> a home made load box that I use.
>
> 2) Switch on power supply at the back.
>
> 3) Connect Green to Black with a paper clip. The fans should spin.
>
> Then, you can use a multimeter to measure the voltages if you want.
> I use a load box, drawing a light load (<100W), to help ensure
> that the power supply will be regulating properly when I measure
> it. I actually test new power supplies, before I use them.
>
> Paul

Paul,
Thanks very much for answering. I understood your explanation - now I
know why the LED on the keyboard was turned on when I turned the back
switch on.

I'm not sure what you meant by "Connect Green to Black". I looked at
all the cables coming from the power supply, and I didn't see anything
green. Only yellow, red, white, black, blue, and purple.
Thanks again, I really appreciate the help.
-Zalek

zalek wrote:
> On Jun 19, 10:57 pm, Paul <nos...@needed.com> wrote:
>> zalek wrote:
>>> Hello, I am trying to build a new PC. After connecting all the parts,
>>> I turned the switch on and... nothing.
>>> I suspect that the power supply is not working, or the circuit on the
>>> motherboard that switches the power supply on is not working.
>>> When I flip the switch on the back of the power supply on, the
>>> keyboard LED turns on for a second. However, when I press the major
>>> switch, nothing happens. No fans move, and there are no noises. I
>>> checked the major switch with an ohmmeter, and the switch seems like
>>> it works.
>>> I'm not sure if the power supply or the motherboard circuit that
>>> starts the power supply isn't working.
>>> So my question is, how can I check if the power supply is working?
>>> Thank you very much
>>> Zalek
>> There is a power supply spec here, so you can see the signal names.
>>
>> http://www.formfactors.org/developer...2_2_public_br2...
>>
>> To start with, the power supply is split into two pieces. The +5VSB
>> output, is available as soon as the rear switch is turned on. The +5VSB,
>> in turn, flows down the main power cable and powers some motherboard
>> logic.
>>
>> The second half of the power supply, operates the 3.3V/5V/12V/-12V
>> outputs. The power is "soft switched" by means of the logic level
>> on the PS_ON# signal. The PS_ON# signal normally is pulled to +5V,
>> by an internal resistor. To start the supply, PS_ON# needs to be
>> grounded (zero volt level).
>>
>> Inside the computer, the chain of command looks like this.
>>
>> Front Motherboard Grounds Main To main ATX
>> Power ------------ Logic runs ----- PS_ON# --------------- part of supply,
>> Switch on +5VSB to operate Cable fans start to spin
>> (momentary (latches when PS_ON# is
>> contact) signal) grounded
>>
>> An ATX supply can be operated on the test bench.
>>
>> 1) Connect a dummy load to the supply. You could use a couple old
>> hard drives, and connect them to the Molex connectors. I have
>> a home made load box that I use.
>>
>> 2) Switch on power supply at the back.
>>
>> 3) Connect Green to Black with a paper clip. The fans should spin.
>>
>> Then, you can use a multimeter to measure the voltages if you want.
>> I use a load box, drawing a light load (<100W), to help ensure
>> that the power supply will be regulating properly when I measure
>> it. I actually test new power supplies, before I use them.
>>
>> Paul
>
> Paul,
> Thanks very much for answering. I understood your explanation - now I
> know why the LED on the keyboard was turned on when I turned the back
> switch on.
>
> I'm not sure what you meant by "Connect Green to Black". I looked at
> all the cables coming from the power supply, and I didn't see anything
> green. Only yellow, red, white, black, blue, and purple.
> Thanks again, I really appreciate the help.
> -Zalek

If you check the formfactors.org PDF file, it has a pinout for the main
connector, with names and wire colors.

Pin Signal Color Pin Signal Color
--- ------ ----- --- ------ -----

1 +3.3VDC Orange 13 +3.3VDC Orange
[13] [+3.3 V default sense] [Brown]
2 +3.3VDC Orange 14 -12VDC Blue
3 COM Black 15 COM Black
4 +5VDC Red 16 PS_ON# Green <---
5 COM Black 17 COM Black
6 +5VDC Red 18 COM Black
7 COM Black 19 COM Black
8 PWR_OK Gray 20 Reserved N/C
9 +5VSB Purple 21 +5VDC Red
10 +12 V1DC Yellow 22 +5VDC Red
11 +12 V1DC Yellow 23 +5VDC Red
12 +3.3 VDC Orange 24 COM Black

HTH,
Paul

zalek wrote:
> Hello, I am trying to build a new PC. After connecting all the parts,
> I turned the switch on and... nothing.
> I suspect that the power supply is not working, or the circuit on the
> motherboard that switches the power supply on is not working.
> When I flip the switch on the back of the power supply on, the
> keyboard LED turns on for a second. However, when I press the major
> switch, nothing happens. No fans move, and there are no noises. I
> checked the major switch with an ohmmeter, and the switch seems like
> it works.
> I'm not sure if the power supply or the motherboard circuit that
> starts the power supply isn't working.
> So my question is, how can I check if the power supply is working?
> Thank you very much

Something really simple to check - Is the power button cable connected
correctly to the motherboard?

Cheers,
Nicholas Sherlock
-----------------
www.Newsgroup-Binaries.com - *Completion*Retention*Speed*
Access your favorite newsgroups from home or on the road
-----------------

zalek wrote:
> Hello, I am trying to build a new PC. After connecting all the parts,
> I turned the switch on and... nothing.
> I suspect that the power supply is not working, or the circuit on the
> motherboard that switches the power supply on is not working.
> When I flip the switch on the back of the power supply on, the
> keyboard LED turns on for a second. However, when I press the major
> switch, nothing happens. No fans move, and there are no noises. I
> checked the major switch with an ohmmeter, and the switch seems like
> it works.
> I'm not sure if the power supply or the motherboard circuit that
> starts the power supply isn't working.
> So my question is, how can I check if the power supply is working?
> Thank you very much
>
> Zalek

You already have received some good suggestions, but I shall make one
more: I always connect the motherboard to the power supply before I
mount it into the case. If you are able to see the POST screen on the
monitor, you know you have the beginnings of a working system. If after
mounting the MB into the case something fails, look for a short on the
underside of the MB or a cable attached improperly. The problem you
described could be a short causing an over current condition, an
undersized power supply, a defective one or other possibilities. It is
always best in my opinion to simplify your problem by establishing what
works and adding components one by one.

On Jun 20, 3:16*am, zalek <zalekbl...@hotmail.com> wrote:
> Hello, I am trying to build a new PC. *After connecting all the parts,
> I turned the switch on and... nothing.
> I suspect that the power supply is not working, or the circuit on the
> motherboard that switches the power supply on is not working.
> When I flip the switch on the back of the power supply on, the
> keyboard LED turns on for a second. *However, when I press the major
> switch, nothing happens. *No fans move, and there are no noises. *I
> checked the major switch with an ohmmeter, and the switch seems like
> it works.
> I'm not sure if the power supply or the motherboard circuit that
> starts the power supply isn't working.
> So my question is, how can I check if the power supply is working?
> Thank you very much
>
> Zalek

You can buy a power supply quick check tool.

"zalek" <zalekbloom@hotmail.com> wrote in message
news:c1477604-06e5-426f-aec2-828767b46380@l64g2000hse.googlegroups.com...
> Hello, I am trying to build a new PC. After connecting all the parts,
> I turned the switch on and... nothing.
> I suspect that the power supply is not working, or the circuit on the
> motherboard that switches the power supply on is not working.
> When I flip the switch on the back of the power supply on, the
> keyboard LED turns on for a second. However, when I press the major
> switch, nothing happens. No fans move, and there are no noises. I
> checked the major switch with an ohmmeter, and the switch seems like
> it works.
> I'm not sure if the power supply or the motherboard circuit that
> starts the power supply isn't working.
> So my question is, how can I check if the power supply is working?
> Thank you very much
>
> Zalek


Double check that the power swich is on the correct connector in the correct
manner. Sometimes you can place them on the connector 90 degrees out of
rotation i.e. Vertically vs horizonataly and it will not work.

Mike

On Jun 20, 9:51*am, smlunatick <yves...@gmail.com> wrote:
> You can buy apower supplyquick check tool.

That power supply tester (quick test tool) is almost useless and too
expensive. But few reasons. A defective power supply can still boot
a computer AND will be reported as good by a power supply tester.
Second, a power supply tester does not report on other failed or good
component of a power supply 'system'. Paul has discussed some parts of
that 'system'

Anything a power supply tester might do is performed by the
multimeter. A defective power supply may only be detected when supply
is under full load from a computer. Meter will do that with a
definitive answer. Power supply tester will not.

Paul has recommended jumpering the green wire to black. Another
useful solution is to measure DC voltage of purple and green wires
both before and when power switch is pressed. Everything in a power
supply 'system' is known in less than 30 seconds by those measurements
and without disconnecting things. Even the power switch is tested. No
useful report is provided by that power supply tester. Disconnecting
may create further failures.

Numbers also make possible useful replies from the better informed.
A power supply tester means that additional assistance cannot be
provided. And finally, a meter means learning how that power supply
'system' really works. Quick tester teaches nothing useful.

smlunatick <yveslec@gmail.com> writes:

> On Jun 20, 3:16*am, zalek <zalekbl...@hotmail.com> wrote:
> > Hello, I am trying to build a new PC. *After connecting all the parts,
> > I turned the switch on and... nothing.
> > I suspect that the power supply is not working, or the circuit on the
> > motherboard that switches the power supply on is not working.
> > When I flip the switch on the back of the power supply on, the
> > keyboard LED turns on for a second. *However, when I press the major
> > switch, nothing happens. *No fans move, and there are no noises. *I
> > checked the major switch with an ohmmeter, and the switch seems like
> > it works.
> > I'm not sure if the power supply or the motherboard circuit that
> > starts the power supply isn't working.
> > So my question is, how can I check if the power supply is working?
> > Thank you very much
> >
> > Zalek
>
> You can buy a power supply quick check tool.

Try the power supply with a known working mainboard.

--- sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/
Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
+Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm
| Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html

Important: Anything sent to the email address in the message header above is
ignored unless my full name AND either lasers or electronics is included in the
subject line. Or, you can contact me via the Feedback Form in the FAQs.