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Desktop won't power on - power supply?


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#1 95PGTTech

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Posted 09 January 2009 - 07:05 PM

The short:

My desktop won't turn on when I press the On button. The switch in the back is turned on. The surge protector is turned on and all other things plugged into it work. I tried a different surge protector. I tried a different power cable going to the back of the tower.

How do I test or confirm the power supply is the issue?








The long:

It's a 3 year old desktop that has really started to show its age as I get more and more into digital photography (about 2mb per picture taken, the software seems to stress the computer out as well). It's a ZT Group computer, running an MSI motherboard and a AMD 64+ processor. It had 2x256mb ram. I removed these two and added 2x1GB RAM (I confirmed I got the same type and it installed easily). I have a 100GB Seagate hard drive in it now, I purchased a brand new 1 terabyte hard drive of the same exact brand from newegg.

It never detected the hard drive properly and diagnosis started from there. I have removed the processor to check the pins upon recommendation but I powered down the unit and have since removed it again and checked I did not break/bend any pins installing it. I did bump the wires going from the switch to the mobo once but I checked and made sure they were all back on how they looked like they came off and it was working fine until all this no power up issue.

I was in the middle of upgrading to vista, trying to upload drivers for the new hard drive when this issue started.

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#2 Sterling14

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Posted 09 January 2009 - 08:03 PM

Welcome to bleepingcomputer! :thumbsup:

I wouldn't doubt the power supply is at fault. A lot of those big computer companies tend to use cheap ones. Do you have another one you can try with the computer, or try this one with another computer?

Edited by Sterling14, 09 January 2009 - 08:03 PM.

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#3 95PGTTech

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Posted 09 January 2009 - 08:22 PM

Not one that I can risk losing.

Someone suggested upgrading the power supply when I upgrade the hard drive, any truth in that? Any connection between the two issues?
Any way for me to check whether I have that switch wired right to the mobo?
The thing is before it went completely dead like now, it would start up for less than a second every 20th or so push. Now is nothing nothing. So I don't really suspect the switch/wiring.





Any comment on the side issue of the computer not recognizing the new hard drive? When I used to fire it up, it used to say...


serial_ch0...hard drive part number
serial_ch1...not detected

still does it with the new one in there in either position, with or without the old one.
I am suspect this old hard drive is corrupt so I wanted to install vista on it and start fresh and have someone pull the info off the old one for me.
vista cannot detect the drive so it asks for drivers. most people are saying sata hard drives should automatically install upon starting vista I should not need any drives. and all are commenting it should be at least detected. it does power up and spin, just never gets on that serial channel list





If I have to buy a hard drive, pick me out on that will power the 1TB hard drive and I'll never have to buy another.

#4 garmanma

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Posted 09 January 2009 - 08:50 PM

Caution: 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 your body may have stored before touching any of the components inside. As a safety precaution you should unplug the computer to avoid electrical shock.
-----------------
The purpose of this procedure is to bypass the motherboard to test the PSU.

Caution:
This procedure will involve working with live 12VDC electrical potentials which if handled improperly may lead to electrical shock. Proper precautions should also be taken to prevent electrostatic discharges (ESDs) within the case of the computer. For safety purposes please follow the instructions step by step.

First, shutdown your computer. Then unplug the power cable going into your computer.

Once you have opened the case, touch the metal of the case to discharge any static electricity.

The connector of the PSU which connects to the motherboard is readily recognizable by the 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.

Posted Image

From the top left to right the pins are 13-24, the bottom from left to right are 1-12.


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. I would suggest that you not leave this connected any longer than is necessary for safety purposes.

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.
---------------------------
At this point you can use a DC Voltage meter to read the different rail Voltages. You will want to insert the black probe into any of the Black (-) sockets, and insert the Red (+) probe in the five different colored sockets, one at a time. Below are the five different colors and their corresponding rail Voltages. The Voltages should be within about ten percent of the given values.

Yellow +12VDC

Blue -12VDC

Red +5VDC

White -5VDC

Orange +3.3VDC
Mark
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#5 95PGTTech

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Posted 12 January 2009 - 05:51 PM

Thanks garm, took me a few days to get back to my garage where my multimeter is, working on the computer right now.

I followed the steps and disconnected the PSU. a light buzzing tone is heard from the back of the case, assuming the power supply. only happens when the PSU is disconnected. then I realized I hadn't read the directions thoroughly - now I unplugged the cable from the back, buzzing/tone gone.

I quickly inspected how both hard drives were hooked up, and the connections at the motherboard. everything seems AOK. pictured below.

Posted Image

I also quickly inspected the eight pins (four two pin) connectors at the bottom of the mobo coming from the on/off switch. interestingly, when you get a good light in there, they are labeled and color coded - smart men. one pin was not connected. I reconnected, put cable back in, and powered up. the hard drives were not connected at this point. it powered up fine, I shut down after a few seconds. I never did see anything on the screen. powered down and correctly hooked up both hard drives. powers up, shuts off immediately. works once every 20 pushes or so.

so back to the diagnosis...

the connector pictured that I am working with appears to be a 20 pin configuration.

Posted Image

holding the connector in the orientation pictured below, my green wire is 4th from the right in the top row, which matches the correct description for #14 as stated below. I jumper that to black pin #15 directly to the right of the green if holding in the pictured configuration. (I took picture of this)

Posted Image

when I reconnect the power cable, leds light up on the front, fans come on, I hear some stuff whirring around. I remove power cable, then remove jumper and reconnect PSU.


moving onto the next step....what is the rail voltage...my two guesses were disconnect the psu again and test from there since it had so many colors, or take reads off one of the supply lines going to the hard drive. problem is, on those lines, I only have black/yellow/red.

is my multimeter set up correctly? dial on correct position? wires on correct tabs below?


Posted Image





I really appreciate the help. This was the technical pin-by-pin diagnosis I was hoping for (similar to an EVTM for my car stuff) rather than just shotgunning parts at the problem.

#6 Sneakycyber

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Posted 12 January 2009 - 06:28 PM

I am unfamiliar with the symbols on your DMM but you want VDC. The best way to test the PS is to unplug all the components from the PS and test the 20 pin plug first, then test your HDD connectors. As for upgrading your Power supply when upgrading the HDD, If your adding and aditional HDD to an exsiting system that is already at the limits of its power supply then yes you should. If your replacing an exsisting HDD with a simlar one then no its not necessary. They also sell Power supply testers at newegg.com. If you are unsure of your abilities with a DMM.

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#7 95PGTTech

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Posted 12 January 2009 - 06:35 PM

I did do the 20 pin test as above, but i am wondering what he means by rail voltages, especially since the hard drive connectors (and the others) only have black, red, and yellow. what is the "rail"?

also, if any blinking lights are diagnostic indicators like they are on most car stuff, with it just sitting there now the green led on the front case flashes, holds for about ten seconds, goes off, waits, then comes back on ten seconds, goes off, etc. Normally when the computer is off this never lights.

#8 Sneakycyber

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Posted 12 January 2009 - 06:43 PM

The 12v rails that are referred to are the number of available 12 volt outputs and their given amperage's. Most new power supplies have multiple 12v rails each at 15 or more amps making them capable of powering more than a power supply with only 1 12vrail. In Automotive terms its like having an bigger alternator. Your main concern is the amount of voltage provided to each connector and that they are within 10% of the listed voltages. So a listed 12 volts only reading 10 means your power supply is toast.

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#9 95PGTTech

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Posted 12 January 2009 - 07:02 PM

so it would be okay if I disconnected the power wire going from the supply into the hard drive and tested red to red and black to black then red to yellow and black to black? should I have the power cord connected at this time (yes...duh...right?)

#10 Sneakycyber

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Posted 12 January 2009 - 07:07 PM

Keep your black probe on the black (any black)and use the red probe to test the Red 5v+, Orange 3.3+, Yellow 12v+, White -5V, blue -12V. All readings are VDC.

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#11 95PGTTech

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Posted 12 January 2009 - 07:10 PM

I only have red, black, and yellow coming from the power supply at the end near the hard drive. should I be looking elsewhere, like at the psu?

#12 Sneakycyber

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Posted 12 January 2009 - 07:16 PM

No those are the correct colors for the HDD the other colors you will find in the 20 pin main harness. The colors and their voltages are consisted no matter where they are found. Black is always ground.

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#13 95PGTTech

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Posted 12 January 2009 - 07:32 PM

I'm an idiot. I think I just realized I'm supposed to be probing the psu with the jumper still connected. wow I'm dumb.

orange = 6
blue = 22.6
red = 9.5
yellow = 22.6
white = 9.5

I confirmed my multimeter is correct, when I switch to the other voltages it says AC volts. and the cords are labeled at the bottom dc volts.


on another note, the computer does do its start up but never put anything on the screen (black whole time) and everything whirrs when I start it with no hard drives connected or with just the power cables connected to it. put a sata cable on either one and you get the one second of power deal shut off.

#14 garmanma

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Posted 13 January 2009 - 12:19 PM

http://pinouts.ru/Power/atx_v2_pinout.shtml
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#15 Sneakycyber

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Posted 13 January 2009 - 01:01 PM

With your 12v reading 22 volts Its safe to assume your power supply is bad. Seems that the voltage regulator has gone bad in it :thumbsup:

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