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

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zalek...

Posted: Thu Jun 19, 2008 4:16 pm

Guest

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...

Posted: Thu Jun 19, 2008 5:27 pm

Guest

On Jun 19, 10:57 pm, Paul <nos... at (no spam) needed.com> wrote:

Quote:

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/specs/ATX12V_PSDG_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

Paul...

Posted: Thu Jun 19, 2008 9:57 pm

Guest

zalek wrote:

Quote:

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

http://www.formfactors.org/developer/specs/ATX12V_PSDG_2_2_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

Paul...

Posted: Thu Jun 19, 2008 11:11 pm

Guest

zalek wrote:

Quote:

On Jun 19, 10:57 pm, Paul <nos... at (no spam) 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/specs/ATX12V_PSDG_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

w_tom...

Posted: Fri Jun 20, 2008 1:04 pm

Guest

On Jun 20, 9:51 am, smlunatick <yves... at (no spam) gmail.com> wrote:

Quote:

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.

larry moe 'n curly...

Posted: Fri Jun 20, 2008 1:40 pm

Guest

zalek wrote:

Quote:

Hello, I am trying to build a new PC. After connecting all the parts,

You don't want to connect _all_ the parts and then test. You should
first connect just enough parts for a barebones system -- mobo, one
memory module, CPU, CPU cooler, graphics card (if the mobo doesn't
have built-in graphics), monitor, keyboard, power switch, reset
switch. Only after you prove that this will boot should you add more
memory, cards, drives, etc.

A common problem that prevents turning on the computer is a short
between the mobo and case, usually around one of the mounting holes or
at a corner (mobos and cases can be warped enough to let them touch --
always support the mobo near the corners, even with stick-on plastic
or rubber feet).

Make sure that the front panel power switch is connected to the
correct pins on the mobo. Not all mobos are labelled clearly for
this.

Unplug the PSU from all the computer stuff, and with it plugged into
the AC power and its rear switch turned on, measure for voltage
between a black wire and the purple wire. If you don't get something
close to +5V, the PSU is bad. Otherwise short the green wire on the
20- or 24-pin connector to any black wire (whaddya mean you don't see
a green wire??? It's between two black wires) to turn on the rest of
the PSU. While the black meter lead is connected to a black wire,
touch the red test lead to an orange (or brown) wire to check the
+3.3V DC, a red wire for the +5V, and a yellow wire for the +12V.
Don't be surprised if each voltage is off by quite a bit because
that's common when there's no load on the PSU. Also some PSUs won't
even start without a load, which can be provided by a hard drive or a
10-20 watt, 5-10 ohm resistor connected beween any black and red wires
(this resistor can get very hot).

PSU testers aren't very good and can indicate everything is OK even
when a voltage is way off. That happened when I tried a CompUSA brand
tester with a PSU whose +12V rail put out only about 10V and wouldn't
even spin the hard drive.

zalek...

Posted: Fri Jun 20, 2008 2:28 pm

Guest

Thanks to everyone a lot for the suggestions.
In the meantime, I connected the motherboard with a known working
power supply, and still nothing happened. I also checked the original
power supply, as you guys suggested (connecting the green and black
wires) and the fan did start spinning. I also checked the voltage.
It showed 5.25 volts. I double checked the master switch, so it seems
that the problem is not with the power supply, but with the
motherboard.
Can you guys suggest anything I can test the motherboard with before I
return the motherboard?
Thanks a lot
-Zalek

zalek...

Posted: Fri Jun 20, 2008 2:52 pm

Guest

On Jun 20, 8:28 pm, zalek <zalekbl... at (no spam) hotmail.com> wrote:

Quote:

I just followed some suggestions, by removing the mb from the case and
connecting it to the powersupply and hard drive. again, no response.
I also noticed that one of the pins on the motherboard said RSVD_DNU.
My case comes without any wire named RSVD_DNU. I'm just curious, is
that important? And what is RSVD_DNU?
thanks again
-Zalek

Michael Kennedy...

Posted: Fri Jun 20, 2008 4:50 pm

Guest

"zalek" <zalekbloom at (no spam) hotmail.com> wrote in message
news:c1477604-06e5-426f-aec2-828767b46380 at (no spam) l64g2000hse.googlegroups.com...

Quote:

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

Sam Goldwasser...

Posted: Fri Jun 20, 2008 6:13 pm

Guest

smlunatick <yveslec at (no spam) gmail.com> writes:

Quote:

On Jun 20, 3:16 am, zalek <zalekbl... at (no spam) 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.

Sam Goldwasser...

Posted: Fri Jun 20, 2008 7:47 pm

Guest

zalek <zalekbloom at (no spam) hotmail.com> writes:

Quote:

Double check the configuration of the motherboard - any jumpers and
other connections and that the CPU is plugged in correctly (if this
applies).

--- 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.

Michael W. Ryder...

Posted: Fri Jun 20, 2008 8:09 pm

Guest

zalek wrote:

Quote:

On Jun 20, 8:28 pm, zalek <zalekbl... at (no spam) hotmail.com> wrote:
Thanks to everyone a lot for the suggestions.
In the meantime, I connected the motherboard with a known working
power supply, and still nothing happened. I also checked the original
power supply, as you guys suggested (connecting the green and black
wires) and the fan did start spinning. I also checked the voltage.
It showed 5.25 volts. I double checked the master switch, so it seems
that the problem is not with the power supply, but with the
motherboard.
Can you guys suggest anything I can test the motherboard with before I
return the motherboard?
Thanks a lot
-Zalek

I just followed some suggestions, by removing the mb from the case and
connecting it to the powersupply and hard drive. again, no response.
I also noticed that one of the pins on the motherboard said RSVD_DNU.
My case comes without any wire named RSVD_DNU. I'm just curious, is
that important? And what is RSVD_DNU?
thanks again
-Zalek

Not knowing what your motherboard manufacturer and model number is I
think the pins are ReSerVeD DoNotUse.

Michael A. Terrell...

Posted: Fri Jun 20, 2008 11:56 pm

Guest

zalek wrote:

Quote:

Didn't you get a manual with the new motherboard?

--
http://improve-usenet.org/index.html

If you have broadband, your ISP may have a NNTP news server included in
your account: http://www.usenettools.net/ISP.htm

Sporadic E is the Earth's aluminum foil beanie for the 'global warming'
sheep.

Baron...

Posted: Sat Jun 21, 2008 11:10 am

Guest

zalek wrote:

Quote:

I assume that you have plugged in the four pin plug from the PSU to the
mainboard ?

--
Best Regards:
Baron.

zalek...

Posted: Sat Jun 28, 2008 8:01 am

Guest

On Jun 20, 8:47 pm, Sam Goldwasser <s... at (no spam) minus.seas.upenn.edu> wrote:

Quote:

zalek<zalekbl... at (no spam) hotmail.com> writes:
Thanks to everyone a lot for the suggestions.
In the meantime, I connected the motherboard with a known working
powersupply, and still nothing happened. I also checked the original
powersupply, as you guys suggested (connecting the green and black
wires) and the fan did start spinning. I also checked the voltage.
It showed 5.25 volts. I double checked the master switch, so it seems
that the problem is not with thepowersupply, but with the
motherboard.
Can you guys suggest anything I can test the motherboard with before I
return the motherboard?
Thanks a lot
-Zalek

Double check the configuration of the motherboard - any jumpers and
other connections and that the CPU is plugged in correctly (if this
applies).

--- 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.

Problem solved!!!! Thanks to all!!
The problem was that the "clear CMOS jumper" was in "Clear CMOS"
position - it should be in "normal" position.
The motherboard was A33G from PC Chips.Now my PC is working!
Other parts I used:

CPU cooler - WATER COOLER XIGMATEK|AIO-S80DP
2GB RAM - MEM 2G|PQI MAD42GUOE R
AMD CPU - CPU AMD|A64 X2 5000+ 2.6G AM2 2M R
case - CASE ATHENATECH|A3602BB.400 BK RT
DVD and HD I used from my old PC. HD had WinXP - I didn't have to
reinstall any software.

One remark - water cooler is pretty big - and takes a lot of space but
fits on the MB. Standard 4 pin ATX power connector must be connected
to MB BEFORE installing the cooler - the cooler blocks the power
connector.

Thanks again,

Zalek

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