Question about Intel D875PBZ Motherboard

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Won't power up CPU fan

The computer was moved a few blocks and won't power up now. The 5 volt led comes on but no fans turn on with power switch (including the cpu fan). Checked the switch, ok. Tried a new (good) supply, no difference. Tried the cpu in another motherboard, ok. Does anyone know where I can get a schematic for the MB? It appears that somewhere I have lost the "power ok" signal going back to the supply.

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  • Anonymous Dec 13, 2008

    Exactly the same problem...

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Pine,

It sounds like you have a short somewhere in the motherboard and should have it replaced. The website for this product can be found here.

Also, I found a technical guide for you which may help.
Download

Please let me know if this helps. Good luck!

Posted on Feb 29, 2008

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Fault finding


Power is going to the motherboard, and you know this by assuming?

An assumption would be you see the Power Supply fan spin, LED lights light up, and maybe computer case fans spin.

Not an assumption, and you would have tested the 3 main voltage power rails, coming out of the Power Supply.

The Power Supply in your computer is an SMPS.
Switched-Mode Power Supply. (Also is known as the short abbreviation - PSU. Power Supply Unit)

http://en.wikipedia.org/wiki/Switched-mode_power_supply

The Power Supply in your computer is a Converter.
It converts HIGH AC voltage into 3 LOW DC voltages.

[Depending on country,
USA = 120 Volts AC. UK = 240 Volts AC. Japan is 100 Volts AC, but may depend on area. Australia = 240 Volts AC. India = 240 Volts AC. HOWEVER, do not write the above in stone. I may have made an error ]

The 3 low main DC Voltages coming out of the Power Supply is;
A) 3.3 Volts DC
B) 5 Volts DC
C) 12 Volts DC

Orange wires carry 3.3 Volts DC
Red wires carry 5 Volts DC
Yellow wires carry 12 Volts DC
ALL Black wires are Ground wires. They can also be called Negative wires.
This is a DC circuit now. There is a Positive, and a Negative.
Orange, Red, and Yellow wires are power wires, and also Positive wires.

The first part of your diagnosis will be to test those 3 main voltage power rails.

[Digressing;
Using an example;
There are many Red wires coming out of the Power Supply.
These are 5 Volt wires. They are Connected TO, the 5 Volt power rail in the Power Supply.
ALL 5 Volt wires end in one place, in the Power Supply.
The 5 Volt power rail.
When you test just ONE red wire, you are testing the entire 5 Volt power rail coming from the Power Supply.

This also goes for the Orange wires, and Yellow wires ]

With the Red 5 Volt wires, and Yellow 12 Volt wires, you could just use a 4-pin Peripheral power cable to check them,

http://www.playtool.com/pages/psuconnectors/connectors.html#peripheral

Multimeter set to DC Voltage, the red (Positive) probe lead of the multimeter; touches the female metal terminal connector, for the Red wire.

http://www.mcmelectronics.com/product/28-9420&utm_medium=Affiliate&ref=cj&utm_campaign=CommissionJunction&utm_source=CommissionJunction?t=2&utm_expid=8634549-14

The black (Negative) probe lead of the multimeter, touches a female metal terminal connector, that goes to a Black wire.

You should be reading 5 Volts DC.

Same thing for the Yellow 12 Volt wire.

With an Orange 3.3 Volt wire, this changes.
A straightened out paperclip is inserted, down into the BACK of the ATX main power cable's connector; AND into a socket hole with an Orange wire in it.

http://www.playtool.com/pages/psuconnectors/connectors.html#atxmain20

http://www.playtool.com/pages/psuconnectors/connectors.html#atxmain24

The straightened out paperclip, slides down into the socket hole, with the Orange wire in it.
Slides down into the socket hole, RIGHT NEXT TO the orange insulation of the wire, and MUST go down far enough; to Touch that female metal terminal connector.

EVERY wire going down into the ATX main power cable's connector, ends in a female metal terminal connector.

Same thing is down with a socket hole that has a Black wire in it.
ALL Black wires are Ground wires. (Negative)
You can choose ANY socket hole that has a Black wire in it.

Now touch the two probe leads of the multimeter, to their respective straightened out paperclips.

Red (Positive) probe lead of multimeter, to straightened out paperclip in Orange wire socket hole.
Black (Negative) probe lead of multimeter, to straightened out paperclip in Back wire socket hole.

You should be reading 3.3 Volts DC.

(Or if your multimeter kit has special probe lead, that would take the place of a straightened out paperclip, of course use it instead)

Know this;
A) If ALL of the LED's ('lights') were on at once, they would use less than 1 Watt of power.

B) EACH fan uses 2 to 3 Watts of power.

C) A typical CPU (Processor) can use 51 to 130 Watts of power.
Just depends on what Processor (CPU) it is.

This is why a Power Supply with a weak voltage power rail, will not have enough power to turn the Processor ON, but will have enough power to light those simpy LED's, and spin fans.

[LED - Light Emitting Diode ]

Regards,
joecoolvette

May 11, 2013 | Dell Motherboards

1 Answer

Fan is running but screen has no signal, ram is checked, i am thinking that something on the motherboard is not working, what can i do


The first thing to check with a desktop computer problem, is the Power Supply.
(Also is the inside of the computer dirty, but I think we have gone beyond that)

A Power Supply with a weak voltage power rail, will not have enough power to turn the Processor (CPU) on.

1) If ALL of the LED's (Light) were on at once, they would use less than 1 Watt of power.

2) EACH fan uses 2 to 3 Watts of power.

3) A typical Processor (CPU) can use 51 to 125 Watts of power.
Just depends on what Processor it is.
(Older processors uses less power than 51 Watts.
Intel Pentium III for one example)

That is why LED's may light up, and fans may spin, but the computer doesn't work. No Processor operating.

Do you have a multimeter to check the 3 Main voltages?
3.3 Volts, 5 Volts, and 12 Volts. ALL are DC Voltage.

[In comparison two D cell flashlight batteries produce 3 Volts DC.
The dangerous AC voltage coming into the Power Supply, is kept contained in the case of the Power Supply ]

Around here ('States') an economical multimeter can be purchased, for around $5 to $12.
I can step by step you through this procedure.

OR;
Do you have a KNOWN to be good, Compatible power supply; that you can use for a Temporary test unit?

[Honey I'm going to borrow the Power Supply out of your computer.
I'll put it back when I'm done.
What's that? I'll be sleeping on the couch?...........lol! ]

Post your findings in a Comment, and then we'll go from there.

Regards,
joecoolvette

Apr 12, 2013 | Motherboards

1 Answer

CPU fan inoperable on HP Motherboard MCP61PM-HM


The switch mode power supply could be faulty
The voltage on the red wire should read 5 volts and the yellow wire should read 12 volts..

Dec 29, 2012 | ECS HP MCP61PM-HM Nettle3-GL8E 6150SE AM2...

1 Answer

Have an asrock 939sata2 I hit the power to turn on the led lights up along with the floppy drive light all the fans come on but that's it nothing else any solution?All the fan motors come on but t


Power Supply with a weak voltage power rail.

[There are 3 voltage power rails. 3.3 Volts, 5 Volts, and 12 Volts. All are DC Voltage ]

Enough power to light LED's, and spin fans, but not enough power to turn the Processor on.

1) If ALL of the LED lights were on at once they would use less than 1 Watt of power.

2) EACH fan uses 2 to 3 Watts of power.

3) A typical Processor can use 51 to 125 Watts of power.
Just depends on what Processor it is.

Suggest you check the three main voltages with a multimeter.
Since the Soft Power On circuit uses 5 Volts, I have a feeling the 5 Volt power rail may be the bad one.

An economical multimeter can be purchased for as little as $5 to $12.
Available in a multitude of stores. An auto parts store is but one example.
Need guidance in using it just post in a Comment.

Or you can borrow a KNOWN to be good, Compatible power supply, and use it for a test unit.

For additional questions please post in a Comment.

Regards,
joecoolvette

Oct 06, 2012 | Sony ASROCK 939Dual-SATA2 / 939DUAL SATA2...

1 Answer

ECS RC410L/800-M (V2.0) motherboard won't boot up. lites the fans and system lights, but no go. replaced video, CPU with 800 fsb from 533 existing and cleared cmos, still nothing. 533 processor creates...


A bad Power Supply with a weak voltage rail, will produce the symptoms you've just described.

1) IF all of the LED lights were on at once, they would use less than 1 Watt of power.

2) EACH fan uses 2 to 3 Watts of power.

3) A typical Processor can use from 51 to 125 Watts.
Just depends on what Processor it is.

You press the Power On button. The first chipset (Integrated Circuit) to receive power is the BIOS chipset.
BIOS detects what devices are installed, does a Ram Memory count, turns the Processor on, and hands the computer over to the Operating System.
(Windows XP is one example of an O/S)

Have you tested the main voltages of the Power Supply?
A) The 3.3 Volt power rail
B) The 5 Volt power rail
C) The 12 Volt power rail

(12 volt rail must be 11 volts or more. Less = new Power Supply)

Post back in a Comment.

Regards,
joecoolvette

Oct 28, 2011 | EliteGroup RC410L/800-M (V2.0)...

2 Answers

I seem to have a problem with the power to my computer. After 2 days of searching all kinds of forums I still haven't found a solution. The computer won't power up, no fans are spinning, not a...


First remove the power plug from the smps and press the power switch few time and wait for few minutes the re plug the power connector to the smps and switch on the computer if you still dont have power then you will have to check whether the smps work to test that its not enough to test the voltage in the 21/24 pin you will have to short the green wire and the black wire and see whether the smps fan is working if the fan is not working then the problem is with smps

Jul 30, 2011 | ASUS Motherboards

1 Answer

Power LED is On but system doesnot start ?


hello, I have a solution for u i think it may help for u.
your problem is:

When u press the start button... the power LED comes on but there is no POST beep or BIOS screen or boot up. The SMPS fan and Processor fans also dont come on at all. there is a small LED next to the SMPS plug on the motherboard that does light up when the system is connected to a power source.
Part of the system configuration is the kind of PSU you have in your system.
SOLUTION IS
So, what kind of PSU?

Try to borrow a known good PSU. Or better yet, see if you can test your PSU in another working system. If you cannot do that, try to borrow a DMM to measure the voltages. Yellow wires should be 12 volts. Red wires: +5 volts, orange wires: +3.3 volts, blue wire : -12 volts, violet wire: 5 volts always on. The gray wire is really important. It should go from 0 to +5 volts when you turn the PSU on with the case switch. CPU needs this signal to boot.

You can turn on the PSU by completely disconnecting the PSU and using a paperclip or jumper wire to short the green wire to one of the neighboring black wires.

This checks the PSU under no load conditions, so it is not completely reliable. But if it can not pass this, it is dead.

Jul 01, 2010 | ASUS P4P800 SE (890552603657) Motherboard

2 Answers

I had a loud fan noise coming from inside my desktop box for a while. One day (& ever since,) when I went to turn the box on, absolutely nothing happened: no fans, no BIOS, no LEDs. I made no config...


This may work however i think by ignoring the sound of the Fan you might have destroyed the cpu and the motherboard.If you can try the processor in another machine you might just have to replace the motherboard only.
Good Luck

Dec 03, 2009 | Intel Motherboard

2 Answers

Installed Crosshair MB in new case. Motherboard LED lights come on but CPU and fan do not light up or turn on. Tried dif power supplies and cases, no luck.


Make sure that the motherboard LED switch on the back panel is set to off and if want to turn it on go into bios and set it. If it is active thru switch and not thru motherboard bios it will not allow you to turn on PC cause it is in maintenance mode.

Oct 26, 2009 | ASUS CROSSHAIR Motherboard

2 Answers

M2N MB LED is on, fan comes on for 2 seconds only


It's a bad power supply. Couldn't be a bad Power On switch, because it turns on for 2 seconds.

You have to have Ram to get the computer to function, besides the processor. All you will see is the BIOS Setup screen.

Been using the same power supply?

The power supply has bad Electrolytic Capacitors in it. These bad 'Caps' in turn make a weak voltage rail. You have three main voltage rails inside a computer power supply.
The 3.3 volt rail, the 5 volt rail, and the 12 volt rail.

With a weak voltage rail, the processor won't have enough power to run.
ALL the lights, (Lamps), use less than 1 Watt.
EACH fan uses 2 to 3 Watts.
Processors use 55 watts to 125 Watts. Depends on the processor.

Jul 25, 2009 | ASUS M2N-E SLI (M2N-E SLI GREEN)...

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