# Failing PSU symptoms



## Jonathan1087 (Dec 30, 2010)

Hello, I'm a novice technician and am just wanting to learn more about the wide variety of symptoms of failing PSU's. Also, rare symptoms that do not often occur, but can be difficult to diagnose. 

I'll begin with my methods of testing a PSU and what I already know (or think I know).
*
EQUIPMENT:
*-I use a simple ATX power tester w/ LCD screen. 24pin capable like the one below.
[url]http://www.amazon.com/24-pin-ATX-Power-Supply-Tester/dp/B0017WP5IW[/URL]
-If it simply doesn't power on at all and it's unclear if it's the PSU or the MB, I just swap it with a new one. 

*WHAT I KNOW (or think I know) -_O
*-Never open the PSU casing unless I am an experienced electrician (I'm not) 
-Some ATX PSU's will have a LED failure indicator that will illuminate or flash on the back of the PSU when it has failed. 
-Swap it with a new one if it's suspected to be faulty or dead
-Use the ATX PSU tester to get a voltage readout for each connector. 
**That's about all I know, and I'm not sure if any of that is wrong or not, I've never been taught to properly troubleshoot an ATX PSU, nor do I barely know anything about the electrician's subject and terminologies. Some enlightenment on understanding more about basic entry level electrical information would be of great help**
-I think I know that Wattage = Volts * Amperage. ex19V * 3.46a = 65.75W)
I use this for calculating voltage for customers AC power adapters for laptops and usually go by a rule of thumb to shoot for plus or minus *.*5 Volts. From my understanding, anything of greater variance in Voltage will either not work, or could damage the DC power jack or MB. 


*What I would like to know:
*-What types of sporadic behavior could a failing PSU display?
**I've "heard" random rebooting if there isn't a consistent and proper supply of power to a device**
**I've also heard of distorted graphics similar to RAM symptoms, (unsure of this one)**
-I know there is much debate on this one, but I'm pretty comfortable with a multimeter. *Which is a better method of testing? Multimeter or ATX PSU tester?* (I have the Driverheaven guide for testing with a multimeter, no need to repost) Just wondering if there were benefits for testing with one over the other. 
-I've heard the terminology "Ripples" tossed around, what does that mean? Is that referring to a fluctuation in power or "not a steady voltage readout" ?


*RANDOM EXPERIENCES:
*-I've only had one weird experience with a PSU. The machine would not power on because the Molex (4pin) connector was plugged into a dead HDD. I guess maybe the circuitry on the HDD board could have been shorting out the PSU? I am clueless on this one, but all I know is I unplugged the HDD and everything else worked fine, replaced it, reinstalled windows to a new one and it was fine. 

*About myself:*
Again, I'm very new to the computer field and I've only been working in the computer repair field for a year now. All of my experience is about 80% hands on, 5% teaching my methods and what I've figured out to newer techs. Tools I use, freeware, etc. 5% of tech talk to my buddy who is more knowledgeable on the subjects than I and 10% *GOOGLE!!!!!! *so I'm about 95% self taught. So far I don't think I'm doing too bad. I would just like some help to stay on the right track of learning from more experienced technicians considering there are no more of those at my place of employment. I know what you're thinking, and yes I am definitely too poor for college. 

Thank you all in advance for any replies, I'm all ears (eyes since it's a forum, but.. you know what I mean). 

Jonathan D Coffey


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## dai (Jul 2, 2004)

failing psu's are not that common

underpowered psu's are a regular occurance

psu problems

shut down and reboots with no bsod

if it has a video card and has startup problems

if it boots into safe mode ok then look at the video drivers or underpower

if it takes a number of restarts from cold to boot up look at the psu

current day computers need 80+ quality units or better

to test for ripple you need appropriate test equipment and above average knowledge to use it

http://www.techsupportforum.com/f210/power-supply-information-and-selection-192217.html


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## Johnny1982 (Oct 15, 2010)

Another way of checking is by using a voltage monitoring tool for the pc like HWMonitor and if the voltages are off by more (or less) than 5% (under load) than what they should be, then it's likely a faulty PSU. BTW, i'm also a Computer Technician and even I'm still learning, especially from the guys at TSF. Thanks TSF.


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## dai (Jul 2, 2004)

software monitors are not that good we prefer looking at the bios readings as the closest to accurate


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## Johnny1982 (Oct 15, 2010)

I've found HWMonitor to be the most accurate, but I agree the Bios is the best place to check.


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## Jonathan1087 (Dec 30, 2010)

Thank you all for the swift responses! Dai, I live in Mobile, AL and we frequently get lots of nasty weather down here, mostly thunderstorms and rain. There is also a small town near us that is at a slightly higher altitude and after every storm, on average of 3-5 out of every 10 computers have bad PSU's or fried AC power adapters (laptops) due to power surges. I've also noticed a lot of Ethernet chips blown off of cards onboard and on PCI cards due to a surge through their Cat5 cable. Very few modem chips get blown off, but some people still use dialup. 
One of my main questions though in the previous post, is using a multimeter more accurate in testing Voltage? Some lower end computer's BIOS menus unfortunately do not have voltage listings for the PSU.

One additional question. If you were in my situation, what would be the best method to teach a newcomer to the tech field about how to test a PSU. I'm actually making it mandatory that the guys subscribe to this forum for tech help that they can't get at the shop. 

Thanks in advance, 
Jonathan.


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## Johnny1982 (Oct 15, 2010)

The worst weather problems I had was also with dialup and before going to ADSL I went through 4 internal modems. Luckily no damage to PSU or Motherboard. But I did here of a case where a guy's motherboard exploded as a lightning bolt hit nearby his house.


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## Jonathan1087 (Dec 30, 2010)

Wow... Sorry for that guy, but all I can say is... "Job Security"


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## gcavan (Aug 13, 2009)

> I've heard the terminology "Ripples" tossed around, what does that mean? Is that referring to a fluctuation in power or "not a steady voltage readout" ?


Ripple is high frequency AC 'noise' which gets transferred onto the DC outputs. Every PSU will have some ripple though it will be at a minimum on better supplies. As stated, you need an oscilloscope to measure it, though you can sometimes measure it with a DMM set to a low AC volt scale.

Whether or not you use a PSU tester module, you should have a decent DMM because there will be times when you will need to track voltage/continuity problems associated with components other than the PSU


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