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Desktop computer will not power off


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#1 onewayjose

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Posted 28 August 2016 - 11:33 AM

-Brief background-  Computer working flawlessly; then I plugged a USB charger for a NITECORE HM20 LED flashlight into it [YES, know now, bad idea :oopsign: ]

Desktop, Processor- AMD Athlon 64 X2 6000 Dual-Core 3.1 GHz, MB- Gigabyte GA-MA785GPMT-UD2H, W-7 Ultimate, PS- Rosewill RP550V2-D-SL 550W. 

 

First thoughts: When the SHUT DOWN is toggled the screen goes off (as normal) but the computer won't power off. Holding the START button on the case (which usually shuts it down) will not shut it down. Unplug the computer and it stops (naturally). Plug it in and it begins running again (but no start up). Have managed a couple times to get it to boot and it works normally. Still when SHUT DOWN it keeps running..  Now, will NOT boot-up again.
Problem is: cannot get access on start-up to the MACRUM REFLECT boot disk.

 

What was done to troubleshoot so far: Power supply voltages to MB checked ok. Wiped the current system HDD and was able to load a fresh copy of W-7 Ultimate. After finishing reload found it would RESTART in the proper manner. SHUT DOWN through proper on-screen manner. Noted fans and lights still running after system shut down. Unplugged power to reconnect the second drive with MACRUM REFLEX system copy on it and found fans and lights to be still running when re-plugged in. Would not boot up- Hard shut-down (panel power switch) still would not work.

Know power supply could possibly be intermittent, but believe in most cases if it is not burned out and is working it could be assumed to not be defective and not be an 'on again-off again' situation?

 

The HM20 is going to be returned and no 'goodies' will ever be plugged into my computer again  :nono:

 

This is WAAY above my pay-grade and any suggestions appreciated- THANKS!


Edited by hamluis, 28 August 2016 - 04:08 PM.
Moved from Win 7 to Internal Hardware - Hamluis.


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#2 onewayjose

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Posted 28 August 2016 - 03:57 PM

Apparently it does not ring a bell with anyone.  It seems to me that possibly the power button on the case, which is hooked to the MB, and has to work a control circuit of some sort that got fried by the 'goodie' device.  If that is the case, it should account for it being stuck in ON and possibly keeping it from posting?  If so, maybe the posting is intermittent which allowed for the fresh w-7 reload..  Pardon and misuse of terminology.



#3 mjd420nova

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Posted 28 August 2016 - 04:19 PM

I have been the bearer of bad news to so many users who INSIST on using the USB ports on their units to power all manner of devices.  The damage to a MOBO can be extensive and expensive.  Lesson learned??



#4 onewayjose

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Posted 28 August 2016 - 05:39 PM

I have been the bearer of bad news to so many users who INSIST on using the USB ports on their units to power all manner of devices.  The damage to a MOBO can be extensive and expensive.  Lesson learned??

 

RUB IT IN :thumbup2:



#5 mjd420nova

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Posted 29 August 2016 - 09:25 AM

You have to face the reality.  Lights, chargers, fans, that use the USB port for power are capable of drawing more power than the MOBO circuits can handle.  Regulator chips and devices get damaged when doing their jobs of protecting the MOBO from serious damage but this results in a blown chip or vaporized trace.  Replacement is possible and when achieved, should be protected by a fuse on standoffs to protect against future faults.



#6 onewayjose

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Posted 29 August 2016 - 10:37 AM

You have to face the reality.  Lights, chargers, fans, that use the USB port for power are capable of drawing more power than the MOBO circuits can handle.  Regulator chips and devices get damaged when doing their jobs of protecting the MOBO from serious damage but this results in a blown chip or vaporized trace.  Replacement is possible and when achieved, should be protected by a fuse on standoffs to protect against future faults.

 

Thanks kindly for the education.  Yes. I know now- too bad knew nothing about it prior.  Life is a learning curve.. :grinner:

I suppose "replacement" is not doable?  - believe it or not I have some electronic circuitry knowledge..



#7 mjd420nova

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Posted 29 August 2016 - 02:58 PM

Replacement is possible but a schematic is desirable to locate the area.  Maybe just a regulator in line with the 5 volts, usually.  I have done a modification on my wife's laptop for that reason.  Extreme case, the trace was fried on the connector, melted the plastic holder and flat ribbon cable.  I replaced the cable and trace with solid wire and added a pico-fuse of one quarter ampere on standoff pins to be easy to replace.  Depends on how serious the damage is.  Most mfgr will take in a board for repair, but usually swap it out if the damage is to the board itself.



#8 onewayjose

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Posted 29 August 2016 - 05:06 PM

Good advice.  Will look for a smoked line when I get a chance.

Thanks



#9 onewayjose

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Posted 30 August 2016 - 09:09 AM

Defective PSU?

Some suggestions elude to the 'green wire' as being the sole connection to the MOBO.  If so, it has to be a control circuit allowing the MOBO to turn the PSU off and on.  Got to thinking and just unplugged the 24 pin main power plug from the MOBO and the PSU still runs until it is unplugged again.  To me, that would suggest the MOBO may have dodged the bullet and the PSU took it in the shorts (no pun intended) sarc.png

 

If the PSU output voltages are present then the control circuit from the MOBO is being negated by some sort of stuck/fried relay system within the PSU.  IS that possible?  If so, is the MOBO not booting because it is required for the PSU to recycle as the first step of the booting process?

 

Realize this is getting a little technical and probably something most do not know, but I do not want to tear down another computer to substitute a 'good' PSU so will have to buy one if what I am thinking is a possibility.

 

Thanks a million for any and all suggestions.


Edited by onewayjose, 30 August 2016 - 09:10 AM.


#10 mjd420nova

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Posted 30 August 2016 - 09:56 AM

It is a simple logic circuit on the MOBO that controls the power supply.  Since the advent of a "dead" front panel, that is, no dangerous voltages (110/220) are present on the front panel.  Instead a low voltage line from the board to the power supply signals when the power supply should turn on or off.  This also means that the power supply is always energized to provide that low voltage.  This is also a lead to other faults that go away when power (AC) is removed from the power supply.



#11 onewayjose

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Posted 30 August 2016 - 06:06 PM

Here is an explanation in detail of PSU operation and troubleshooting.  Hope it is OK to post it here http://www.aitechsolutions.net/pchwtrblsht.html

 

My- ON SIGNAL#14- is 5.14v (load or no load)

       STANDBY #9- is 4.75v (no load) and 1.74 (load- 24 pin plug connected to MOBO)

       POWER GOOD/OK SIGNAL #8- is .8v (under load) and should be 2.5v or higher.

 

If I read this all correctly, the MOBO is not confirming the power check so the #8 is low (unacceptable) and that should be why it will not boot.  The persistent PSU running should be controlled by the ON SIGNAL (which is correct voltage) but still continues to run when disconnected from MOBO.  The STANDBY drops to 1.4v under load (24 pin plug connected to MOBO) which is out of whack.  From all this it would appear the PSU is screwed-up, and quite possibly the MOBO is kaput also. 

I have had my FUN digging into this.  It is an older computer and It is probably time to recycle it for parts.

Appreciate your time and interest; Hope this referred to article will help others. Have a GREAT day!



#12 onewayjose

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Posted 31 August 2016 - 05:54 PM

Apparently I'm missing something.  Why does this post show zero replies and zero views when mjd420nova has responded?



#13 onewayjose

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Posted 01 September 2016 - 09:16 AM

Apparently I'm missing something.  Why does this post show zero replies and zero views when mjd420nova has responded?

DUMB ME- Posted in the wrong topic- SORRY! :scratchhead:



#14 hamluis

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Posted 01 September 2016 - 10:19 AM

Nothing to be concerned about :).  Topics get moved every day...and the old/original site where posted will show whatever activity there was at the time that it was moved.  But clicking on the topic will take you to its new location.

 

Louis



#15 onewayjose

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Posted 01 September 2016 - 02:27 PM

Thanks Louis, have a great day!






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