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Intermittent won't reboot: mobo, mem or PSU?


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#1 Blues4est

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Posted 08 June 2015 - 09:18 PM

Have a phenom II X2 on a GA-MA785GM-US2H and 2 GB of Geil ram (DDR2 800, unganged) and PSU is a Corsair CMPSU-400CX. Every 5 months it'll refuse to reboot. Nothing, black screen. Then a day or two later it's fine and runs ok for another 5 months. Now problem is every day. It will boot but if I reboot as a quick reset for the internet connection I get a black screen. No signal. Keyboard and leds light like POST is running from BIOS.

 

I notice leds, fans and drives spin. Always boots cold. I use multiple OS's, all on newer sata hard drives and they all work. (No viruses, I use Sandboxie, Avast and Malwarebytes once in a blue moon.) I've pulled the card and am using mobo graphics  - didn't put it back in when I pulled everything and re-seated one by one. Only forgot the power plug to mobo but I get power since I see leds, hear drives, etc. CMOS batt. was changed 1 yr ago, time always seems ok.

 

I haven't reset BIOS to hear the POST beep but I will. All caps look ok. I re-pasted the cpu when I pulled/re-set everything 2 days ago. Runs fine when it boots. Haven't checked any logs, my bad.

 

I have believed it's an intermittent mobo problem but (more) recent reading makes me think it could possibly be the PSU. I'll switch that out and try multiple reboots tommorrow. I can't believe it's ram since it seems more like a connectivity issue... Or mobo.

 

I plan to buy a new mobo and ram soon as an upgrade, unless I can verify it's the PSU (Tester is a cheap 500w), but would like to keep the system if I can discover a solution.

 

Don't have other ram to test/don't know anyone who has. If I can't pinpoint what is lame I'll have to rely on a backup pc for a month. That's another whole story : (

 

Any thoughts would be greatly appreciated. From bleeping's posts I find some tips stating try loosening mobo screws, re-checking for anything w/might short. Hey, at least it's a hardware problem and not a software issue.

 

 

Thanks in advance,

 

Blues



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#2 YeahBleeping

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Posted 09 June 2015 - 07:52 AM

I am leaning towards the power supply but it could also be a faulty/bad switch on the computer's case.  You can try pulling off the power switch cable from the motherboard and using a screwdriver to 'short across for just a second' the power connector pins when you cannot get the pc to boot and see if it works.  If it does than I'd say you have a faulty switch.  If it doesn't then I would say you have a power supply that may be going bad.  I don't think it is a short on the mainboard standoffs because my thought is if it were that than it would not boot 'intermittently' .. it simply would not boot at all. Sorry I cannot find a video showing how to do this.  Hopefully you understand what I am saying

 

Found a video explaining.


Edited by YeahBleeping, 09 June 2015 - 08:33 AM.


#3 dc3

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Posted 09 June 2015 - 11:02 AM

The problem with troubleshooting this problem is that it is intermittent.  

 

The power button is a momentary switch.  It's like the old doorbell button which when it is pressed will ring the bell and will continue to ring until button is released.  These switches usually will either work or fail completely.  As suggested above you can use a small slot type screw driver to short the two header pins which the two leads of the power button are plugged into.  Or you can use a multi-meter on the Ohm scale to see if there is continuity through the switch.

 

When this switch is pressed it closes contacts on the motherboard which in turn start the PSU.  You can test the motherboard for this by using the instructions below.

 


The purpose of this procedure is to bypass the motherboard to test the PSU.
 
When a computer begins the boot process the motherboard initiates the start up of the PSU. Because of this it is difficult to determine whether the problem is with the motherboard or the PSU when a computer shows no signs of starting up. The purpose of the procedure is to determine if the problem is with the motherboard or the PSU.  For safety purposes please follow the instructions step by step.
 
Caution:  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.  The risks are minimal, but are there nevertheless.  If you are uncomfortable doing this procedure I would suggest  you not try this.  Anyone using this tutorial will be doing so at their own risk. 
 
There are electronic components 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 charge before touching any of the components inside.
 
Shut down your computer, then unplug the power cable from the rear of the computer.  To reduce the possibility of any shock press and hold the power button for thirty seconds to discharge any capacitors still holding a charge.
 
The connector of the PSU which connects to the motherboard is readily recognizable by the large number of wires in the bundle.  To disconnect it you will need to press on the plastic clip to disengage it and then pull the connector up and away from the motherboard.  Please take notice of the location of the locking tab and the notch on the socket of the motherboard, this will only connect one way as it is keyed.  This wire bundle will have a memory of the way it has been installed and will want to bend back that direction, you may have to play around with it to find a position that the connector will stay in the same position while you run the test.
 
th_main24index.jpg
 
From the top left to right the pins are 13-24, the bottom from left to right are 1-12.
 
Below are the pinouts for the 20 and 24 pin ATX form factor connectors.
 
atxpinout_zpsfe72bf61.png
  
Please notice that there are PSUs with 24 pin and 20 pin connectors, the location of the green wire in the 24 pin connector is #16, and the green wire in the 20 pin connector is #14.  If you look at the connector with socket side facing you and the clip on the top the number one pin will be on the bottom left corner.  This makes the pin out for the 24 pin connector from left to right 13-24 on top, and 1-12 on the bottom.  The pin out for the 20 pin connector from left to right is 11-20 on top , and 1-10 on the bottom. If you look at the connectors you notice that these are sockets that fit over the pins on the motherboard where the PSU cable attaches, this is where you will place the jumper.  For a jumper you will need a piece of solid wire about the size of a paper clip (20-22 awg), preferably a wire with insulation.  It will need to be large enough to fit firmly into the socket so that it will not need to be held in place while testing.  You are at risk of electrical shock if you are holding the jumper when you power up the PSU.  Insert one end of the jumper into the socket of the Green wire, and insert the other end into the socket of any Black wire.
 
Once the jumper is in place plug the cord back in. If the PSU is working properly the case fans, optical drives, hdds, and LEDs should power up and remain on.  
 
To reconnect the 20/4 pin connector unplug the power cord, remove the jumper, and reconnect the connector. Take a moment at this time to make sure that nothing has been dislodged inside the case.
 
====================
 
If you want to test the PSU rail voltages, use the instructions below.
 

Reading and Testing Desktop PSU Rail Voltages
 
Caution: Please read the following 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
 
 
 
 
 
 
 
 
 
 
 
 
 
 

Edited by dc3, 09 June 2015 - 11:07 AM.

Family and loved ones will always be a priority in my daily life.  You never know when one will leave you.

 

 

 

 


#4 Blues4est

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Posted 09 June 2015 - 01:14 PM

Thanks guys,

 

I'm testing an Antec right now and wanted to surf a little before I try rebooting. Will copy instructions and test using my MM. Hope to post my results soon. Can't say enough for thoroughness, now if I could only pronounce everyone's handle.

 

Thank you very much,

 

Blues



#5 dc3

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Posted 09 June 2015 - 01:25 PM

I can make it easier in my case.  Arachibutyrophobia is not my username, it's dc3. :grinner:


Family and loved ones will always be a priority in my daily life.  You never know when one will leave you.

 

 

 

 


#6 dc3

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Posted 09 June 2015 - 01:28 PM

The plugin could be corrupted.

 

https://support.mozilla.org/en-US/kb/refresh-firefox-reset-add-ons-and-settings


Family and loved ones will always be a priority in my daily life.  You never know when one will leave you.

 

 

 

 


#7 Blues4est

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Posted 11 June 2015 - 04:41 PM

Well, apologies for the wait. Two rainstorms dumped on us and I'm busier than a monkey's somethin-or-other. My old Corsair 400W passed both tests. The voltages were: 3.416-3.418, 5.10 and 12.18-12.31. Damnedest thing but a new PSU and I can reboot all day.

 

Unless it's something the Corsair only does when warmed up I can only guess it has to do with the case switch or pins on the mobo. I'd really rather it be the PSU for a few reasons. I'll try the startup by screwdriver to pins routine w/ I haven't tried. 

 

I may try rigging up a set of wires to the pins to see if that changes anything over time.

 

 

Kudos to both of you for all your help in diagnosing. I guess if I had to pick a best ans it'd have to go to dc3 what w/all that information. Thank you both vy much,

 

Blues






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