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is my m/b dead


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#1 merv70

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Posted 10 September 2014 - 12:36 PM

changed a rear fan now it won't start got led light on the board to light thats it, checked the voltage from the p/s with the paper clip both case fans and the p/s fan came on but not the cpu, all the voltage from the p/s was good.So i checked the cpu fan header and no volts i think there should be 12 volts there           what do you all think-----------m


Edited by hamluis, 10 September 2014 - 01:12 PM.
Moved from XP to Internal Hardware - Hamluis.


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#2 Aerys

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Posted 10 September 2014 - 01:18 PM

Do you have another fan you can try plugging into that fan header? Sounds like you have troubleshooted most possibilities and that header seems dead. If the motherboard is still under warranty maybe you can RMA it.


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#3 dc3

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Posted 10 September 2014 - 03:52 PM

If you were referring to jumping out the green wire and a black wire to test the PSU you need to realize that all this does is bypass the power switch which initiates the start of the PSU.  If you are trying to determine if the is a voltage problem with the PSU you need to use a voltmeter to read the rail voltages with a load on it to receive accurate readings.

 

Reading and Testing Desktop PSU Rail Voltages
 
Caution: Please read this before continuing.
 
 
* Since it will be necessary for your computer to be on during this procedure, you need to be aware that you will be working with live 12Volt DC potentials, which if handled improperly may lead to electrical shock. 
 
* There are electronics inside the case that are very susceptible to electrostatic discharges. To protect your computer, touch the metal of the case to discharge yourself of any electrostatic charges before touching any of the components inside.
 
* If you are not comfortable doing this procedure, then I would suggest that you not use this tutorial. The risks involved are minimal, but are there nevertheless. Anyone who uses this tutorial will be doing so at their own risk.
 
 
There are two devices commonly used to read the rail voltages: a PSU tester, and a multimeter. 
 
The PSU tester is the easiest to use since all that is necessary is to plug the different connectors into the tester and read the results on the LCD display. The problem with most of these is that they only perform a pass/fail test.  They will not provide you with actual voltage readings.
 
There are a variety of multiple meters, but this tutorial will address Analog and Digital multimeters. The advantage of these meters is that you will be able to obtain accurate real time voltage readings.
 
For those of you who wish to know more about multimeters there is an excellent article in Wikipedia.
 
 
Analog Multimeter
 
th_analogedited.jpg
 
 
An Analog multimeter is a little more complicated to use. Both Analog and Digital multimeters need to be set to the appropriate voltage, but with an Analog multimeter, you will need to choose the voltage range and must read the proper scale. 
 
The Analog multimeter uses a needle display which moves from 0 across the scale until it reaches the voltage being tested. This multimeter has five major linear divisions with multiple scales to read a variety of ranges. An example would be three different ranges. The first is graduated in increments of 0 through 5, the second, 0 through 10, and the third, 0 through 25. Each of these ranges are subdivided into divisions that are graduated into tenths. In order to read 12 volts the 0 through 25 range would be the appropriate one. 
 
Because DC voltage has positive and negative potentials this device is polar sensitive, this means that if you reverse the two probes when reading a positive DC voltage it will read as a negative voltage. This is actually necessary to read negative DC voltages. The two probes are differentiated by their color, Black (negative), and Red (positive). To read a positive DC voltage, the correct probes must be used with their corresponding potentials (positive to positive and negative to negative). 
 
With the probes being used normally to read a negative DC voltage, the needle moves from the 0 to the left, "pegging" the needle. By reversing the probes you can properly read the negative voltages.
 
Digital Multimeter
 
th_digitalmeteredited.jpg
 
 
The Digital multimeter (DMM) is much simpler to use. As was mentioned previously, you will need to set the appropriate voltage. One of the advantages is that the DMM has an LCD display with a numeric readout, so there are not any multiple scales to read. Another advantage is that most DMMs are autoranging when reading voltages, which means that you will not need to set the range with these DMMs. A DMM will read both positive and negative DC voltages and display them correctly. When reading a negative voltage, a minus sign will appear on the display before the numeric value. This still is a polar sensitive device, so you will still need to use the positive and negative probes with their corresponding potentials. 
 
There are five different DC rail voltages which are color coded. The Black wires are always negative.
 
Yellow +12VDC
 
Blue -12VDC
 
Red +5VDC
 
White -5VDC
 
Orange +3.3VDC
 
There are only three voltages that can be measured easily without disconnecting the 20/24 pin connector from the motherboard: +12V, +5V, and +3.3V.
 
The +12V and +5V voltages can be read from a four pin Molex power connector.
 
Four pin Molex power connector
 
th_250px-Molex_female_connector.jpg
 
 
The same voltages can be taken from a four pin SATA power connector, but in order to read the +3.3V you will need to read this from a five pin SATA power connector as seen below.
 
Five pin SATA power connector.
 
th_sata-power-cable.jpg
 
To read these voltages you will need to insert the Black (-) probe into any of the black  sockets, and insert the Red (+) probe in the different colored voltage sockets.   To read the voltages from a SATA power connector it is easiest to insert the probes into the bac k of the connector where the wires enter.  Unfortunately the sockets of the modular SATA power connectors are not accessible from the back, so the readings will need to be made from the socket side.  Some probes are going to be too large to fit in these sockets, so you may need to insert a piece of wire into the socket of which you want to read the voltage of and place the probe on this for your reading.  To reduce the potential of creating a short I would suggest taking the ground potential from another connector so that the two wires will remain physically separated.
 
Caution:  It is very important to make sure that you don't allow the two probes to touch each other when taking the voltage readings.  This will cause a short which could damage the PSU or other components.
 
To get accurate readings of the rail voltages it is important that there be a load on the PSU. In order to do this I would suggest downloading Prime95 and run the Just Stress Test for this purpose. This program was designed to be used by overclockers to put a full load on the RAM and CPU to determine the stability of their overclocking.  Because of this it will put stress on the CPU and RAM which will create higher than normal temperatures.  For this reason I would suggest not running this program any longer than is necessary.  I would also suggest that an inspection be made of the interior of the case to make sure that there isn’t an accumulation of dust which would impede adequate cooling.  Pay special attention to the heat sink and fan assembly on the CPU.  If there is a dedicated graphics card with a fan installed on it, look at this fan as well.      
 
 
Readings should not have variances larger than +/- five percent.  
 
Maximum.........Minimum
12.6V.................11.4V
5.25V.................4.75V
3.47V.................3.14V

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#4 Joe C

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Posted 10 September 2014 - 06:02 PM

 

The PSU tester is the easiest to use since all that is necessary is to plug the different connectors into the tester and read the results on the LCD display. The problem with most of these is that they only perform a pass/fail test.  They will not provide you with actual voltage readings.

That's not true.

I have a PSU tester and it does have an LED numerical display of the actual voltages that supposed to be within +- 0.1v accurate, Plus it will test the Power Good circuit also. I think your referring to the old style with about 5 LED lights which has no display at all, and it only test a 20 pin mother board connector. The newer styles use 24 pin board connector, Sata, Floppy and older rail molex types. Please check these newer power supply testers out for yourself.

It's way too easy to short your live probes with a digital/analog volt meter while attempting to test something like a Sata connector


Edited by Joe C, 10 September 2014 - 06:14 PM.


#5 dc3

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Posted 11 September 2014 - 08:47 AM

 

 

The PSU tester is the easiest to use since all that is necessary is to plug the different connectors into the tester and read the results on the LCD display. The problem with most of these is that they only perform a pass/fail test.  They will not provide you with actual voltage readings.

That's not true.

I have a PSU tester and it does have an LED numerical display of the actual voltages that supposed to be within +- 0.1v accurate, Plus it will test the Power Good circuit also. I think your referring to the old style with about 5 LED lights which has no display at all, and it only test a 20 pin mother board connector. The newer styles use 24 pin board connector, Sata, Floppy and older rail molex types. Please check these newer power supply testers out for yourself.

It's way too easy to short your live probes with a digital/analog volt meter while attempting to test something like a Sata connector

 

You need to read more carefully.  If you had you would have found that I stated that "most of these", I know there are testers  which provide more than a pass fail.  But you still will not get the accuracy that you can get with a voltmeter with a load on the computer. 


Edited by dc3, 11 September 2014 - 08:48 AM.

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#6 Joe C

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Posted 11 September 2014 - 08:52 AM

You can't measure the load with a volt meter....You will need to use an AMP meter

 

You made the implication that most power supply testers do not measure volts, I only stated that is not correct, You will not find those old style of power supply testers on the market any more. You neglected to state in your original post that there are power supply testers that do provide an accurate read out of voltages from the power supply, The +12v1, +12v2, -12v, +5v, +3.3v, +5vsb and PG (Power Good)  Which is misleading to anybody reading your original post


Edited by Joe C, 11 September 2014 - 09:04 AM.


#7 dc3

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Posted 11 September 2014 - 09:01 AM

Joe C   The instructions are for measuring the rail "voltage", the current does not matter in this instance.

 

You posted that you can't purchase "those old style of power supply testers", check this out.

 

You are getting off topic.  If you wish to pursue this I would suggest opening a topic in an appropriate forum to address this.


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#8 Joe C

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Posted 11 September 2014 - 09:12 AM

Just be more accurate and up to date when you make recommendations for testing power supplies, you link states that it does support my recommendations for a power supply tester, in that it does display voltage readings with a power good reading too

Your link

http://www.superbiiz.com/detail.php?p=PS-TEST228&c=fr&pid=5a2b12d7366e0c5f20c186b09ea61596984562ea2d1dde08607bf89c4d0b5a6e&gclid=CKaJnaKp2cACFZSIfgodThYAPA


 


  • Specifications

    • Mfr Part Number: PS-228

    • Feature:

      • Easy to check ATX power supply

      • Accurate voltage indicator +/- 0.1V (+12V1/+5V/+3.3V/5VSB/+12V2/-12V)

      • ATX P.G. value display

      • Lower or higher P.G. values alarm

      • ATX output connectors check

      • Lower voltage detected alarm

      • Over voltage alarm

      • No voltage detected alarm


    • Connectors: 20/24pin Connector; 4/8pin CPU Connector; Floppy Connector; HDD Connector; 15Pin SATA Connector; 6/8pin PCI-E Connector


 The topic is testing a motherboard, and you recommended to test the power supply, I'm only clearing up a fact, Yes using a volt meter is accurate provided it is a digital meter, there's no way to accurately use an analog meter to define with +- 5% of any low voltage readings. Because those meters need to be adjusted on a regular basis. A Power Supply tester is accurate within 0.1volts and a much safer method to use

An analog meter is good for measuring high voltages for your home outlets and such where the +- percentages are not that critical

 

This may be the idiot light tester you are referring too? I had one of these testers too way way back before 24 pin connectors, And I can't find any currently for sale today from any popular retailers. This is a pic of one I at one time used

idiotlighttester.jpg


Edited by Joe C, 11 September 2014 - 09:37 AM.


#9 dc3

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Posted 11 September 2014 - 09:38 AM

You are off topic.  Either stick to the topic or start your own topic.  This is not fair to the person who started this topic.


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#10 Queen-Evie

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Posted 11 September 2014 - 09:55 AM

This is not the place to debate over power supply testers and voltmeters and whatever else you are debating about.

It detracts from the topic.

Please keep ON TOPIC. If not kept ON TOPIC it will be closed which as stated not be fair to the OP.

#11 merv70

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Posted 11 September 2014 - 11:38 AM

hello all thanks for all the replys good info,i have pretty much ruled out power supply problems as i stuck it in a friend of mines old xp machine and all the fans worked

so i guess it is the m/b  or the switch if i jump the switch g/b with the paper clip all the fans start accept the cpu fan.the m/b is a intel 865 perl if that helps it might be i don't have all the plugs on the on the front panel connected right,there is three of them do i need to plug them all in for the switch to work or can i just use the on/off plug and try different leads          ps will doing that hurt anything           thanks       m          p/s    i do have a green led  light working on the mother board


Edited by merv70, 11 September 2014 - 11:43 AM.


#12 rotor123

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Posted 11 September 2014 - 12:16 PM

Hi Merv

If Your power supply worked in another computer and it started up and ran fine then it is most likely OK.

What I would like You to do is post a nice clear picture Of Your Motherboard. I suspect that You have bad capacitors on it as I have seen those on that vintage Intel Motherboard in the past.The Only wires needed to the front of the computer are the power switch and even that is optional for testing as You can momentary close the two pins with a small screwdriver to turn it on. That would also eliminate the Switch as the problem.

 

I will say that in 16 years of computer repair I saw a actual bad power switch once.

Manual is here http://downloadmirror.intel.com/15200/eng/D865PERL_ProductGuide03_English.pdf

Go here and look on the right side where it says Examples of Bad caps, Look for any bulging or pushed up capacitors. If You see any You most likely have a problem and the motherboard would need repair.

 

Good Luck

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#13 dc3

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Posted 11 September 2014 - 12:17 PM

You have already demonstrated that the PSU starts once it is initiated by shorting the green and a black wire.

 

You can now determine if the switch itself has failed.

 

Open the case, and trace the two wires from the power switch to the header pins it is attached to on the motherboard.

 

Once you have located the two header pins remove the two wires from the switch.

 

Take a screw driver and short the two pins very briefly.  This should initiate the startup if the computer is working properly.


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#14 merv70

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Posted 15 September 2014 - 10:26 PM

I will try to jump the switch wires.Rotor123 said something about caps i did find one that was domed i replace it with the same size i figured that was the problem but no dice

what bothers me is the 4 pin power connecter has 12 volts but nothing i'v tried will get the processor fan to run and don't think the computer will ture on if processor fan is not running.I don't think i will invest to much money into this old computer i'm retierd so i have more time, besides this was i first build hard to let it go.I'm kind of leaning toward a m/b problem. I have no idea what to look at for a new computer        thanks again for all the replys------m



#15 rotor123

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Posted 16 September 2014 - 03:49 PM

Hi

FWIW replacing capacitors is more involved than just the Capacitance and Voltage and Temperature ratings. Capacitors from different manufacturers and lines by the same manufacturer have different AC resistance's and so on.

 

You can read more details on Badcaps.com

I always used Nichicon or Rubycon brand, their better quality line. Polymers are even better and I used them on certain Dell models that had a lot of failures due to airflow and cooling.

 

Good Luck

Roger


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