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Power Supply issue?


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#1 Aikaterine

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Posted 16 December 2012 - 05:41 AM

Hello everyone, I am new here and kind of a computer noob so I will probably post here often. I'll start by saying I have a Lenovo desktop (S/N: ES06811776)and from what I was told the motherboard is a G41 Motherboard (exactly like that.)

So here recently I have been playing a game called Guild Wars 2 and this computer runs it pretty well in every other aspect except for the video RAM which is only about half of what it should be. The card is not really a card but a chip set (Intel® G41 Express Chipset). For Christmas, I decided to ask for a new graphics card and found one I wanted but also found out my mother had one in her computer that she no longer uses because it did not work. It is a GeForce 9400GT DDR2 1024MB PCIe 2.0. Unfortunately, it requires 300W from the power supply when the original from this computer only has 180W. Naturally, I asked to use the power supply from the not working computer which was 750W and she said yes.

I had a bit of help taking the old out and putting in the new one as well as the card. But as I turned on the computer, I noticed the lights that shine from the On button were not lit but every fan in the computer was working. Another odd thing was that the monitor was not displaying anything like the blue plug had been removed or loose. After a few tries with tightening the plugs for the connectors (there were only 4), 3 beeps in a row came from the computer..a few seconds later, the same beep pattern came through.

This power supply has 8 divided cords. About two with the L shaped connectors with 3 on each one. (those and the 2 cords into the motherboard were the only ones needed). My question besides wth is going on with this is: Is it possible that a few of those L shaped connectors dont work? The computer it was in was taken to geek squad and had multiple computer repairmen and all of them have stated that the power supply is fine.

I hope my story wasnt too confusing, I have a hard time explaining computer stuff when I don't know much about it to begin with. I hope I can figure out what is wrong.

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#2 dc3

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Posted 17 December 2012 - 06:48 PM

It would help a great deal if you were to post the Model of your Lenovo.

It would also help to know the make and model of the PSU that was in the other computer.

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#3 Aikaterine

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Posted 17 December 2012 - 10:34 PM

The model for the desktop is: 7724-1AU.

And the PSU is: Diablotek PHD Series PHD750 750W ATX12V / EPS12V Power Supply

#4 dc3

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Posted 18 December 2012 - 09:35 AM

You may have to enter the BIOS and enable the dedicated card.

There should be a power connection for the CPU, is it connected?

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#5 Aikaterine

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Posted 18 December 2012 - 03:38 PM

I connected everything in the places that it should have been. To test if it was the card, I even took the card out and tried it again. If I cant start the computer up, I cant go into bios.

#6 dc3

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Posted 18 December 2012 - 03:49 PM

Try booting into Safe Mode. Safe Mode uses a limited number of native drivers, one of these is a video driver. This means that your monitor should work with this driver as it replaces the other.

my mother had one in her computer that she no longer uses because it did not work


Take your mother's card out and see if it will boot.

If that doesn't work, replace the PSU the one that you replaced.

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#7 Aikaterine

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Posted 19 December 2012 - 01:18 AM

I really don't think it's the card at all. Because when I put the 180w power supply back into the computer, it worked just fine. I think the entire problem is the power supply.

#8 dc3

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Posted 19 December 2012 - 07:53 AM

If you are sure of your connections and replacing the smaller PSU allows it to run then it would definitely appear to be the PSU.

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#9 Aikaterine

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Posted 21 December 2012 - 12:26 AM

Well my other question was: Is it possible that it could be some of the connectors or wires that arent working? Since the fans came on and such on the motherboard and graphics card?

#10 dc3

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Posted 21 December 2012 - 09:38 AM

Even if it is a bad connector the bottom line is that it does not work for your application.

If you want to determine exactly what is happening with the different connectors use the instructions below.

You can perform this test with the PSU outside of the case.

On the motherboard there is a header with two pins which the two wires that go to the power button attach. When you press the power button it shorts these two pin which initiates the PSU. In order to turn the PSU on with it outside of the case you will have to physically short the green wire and any black wire in the 20/24 pin connector, it will look like the picture below.

Posted Image

Make sure that the PSU is unplugged from the wall receptacle before proceeding, if the PSU has a on/off switch turn it off. You will need a piece of wire about the diameter of a paper clip, take this and insert one end of the wire in the green wire socket and the other end in any black wire socket. Once this is done plug the PSU power cord back into the wall receptacle, if there is a on/off swithc turn it on, the fan should be running now.

Use the instructions below to perform test the rail voltages of each connector.

Reading PSU Rail Voltages

Caution: Please read this before continuing.


∑ Since it will be necessary for the PSU 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.


∑ 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

Posted Image


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

Posted Image


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

Posted Image


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.

Posted Image

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 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 isnít 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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#11 Aikaterine

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Posted 24 December 2012 - 08:11 AM

So will there be a certain type of power supply that I will need for my motherboard or does that not matter?

#12 dc3

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Posted 24 December 2012 - 08:58 AM

Your PSU is a form factor ATX which is the industry standard. This means that you will want a ATX type PSU of a wattage that will be sufficient for your computer's needs.

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