Tag Archives: power supply

Fast video cards: watch your power supply.

Computer Aid Posted on by

This PC had many problems. On the surface, it should have been quite reliable:

  • Core2duo E4300 (1.8 Ghz)
  • gigabyte 9800 GT
  • 4 X 1Gb DDR2 RAM
  • 2 X HDD

But it would often crash, generate BSODs, sometimes wouldn’t start, sometimes the bios would say “overclock failed” (it wasn’t overclocked)…

A few months prior, I had pinpointed a power supply issue (it was an old 500 Watt PSU, so I replaced it with an 860 Watt unit).

Well, after a lots of trial and error, I eventually unplugged most devices (ie only 1 stick of RAM, 1 HDD, 1 DVD drive… and then I noticed that the PC would fail when I started a graphics-intensive screen saver (Hyperspace from http://www.reallyslick.com).

The 2 month old PSU would make a high-pitched squeal for about 2 – 10 seconds, then the PC would “die”.

I was scratching my head thinking: the PSU must be powerful enough to handle the PC…

I plugged in a cheap video card, and the PC suddenly became rock-solid… no weird errors.

9800gtI researched the power consumption of the 9800GT card, and I see it uses anywhere between 150 and 250 Watt!

OK, its quite possible that the video card drains so much power, that some PSUs just can’t handle it.

I replaced the 860 Watt Power supply with a similar (but better quality) one, and everything ran well once again.

I returned the PC to the customer, with a warning of possible future problems: if this starts happening again, you will need to buy a much more expensive, 1000 Watt power supply.

So I re-learned something: a high-end video card will sometimes force you to buy a high-end power supply.

The smell you’ll never forget.

Computer Aid Posted on by

In my many years servicing electronics be it, TV, industrial electronics or computers, there’s something that ties it all together. That oddly enough is a smell. The smell you’ll never forget.

One day I came home from a hard days work to find my wife quite upset. Just an hour earlier she had found the house full of smoke. In a near panic she called the fire brigade who dutifully sent a crew around to investigate. They found no flames, just smoke. They looked in every room, in the roof space and under the floor but found nothing. They declared it safe and left.

As soon as I walked through the front door it hit me. The smell you’ll never forget. I went straight over to the TV sitting in the lounge room which was located not far from the front door. The odour, as I expected was much stronger there. Pulling the back off the TV revealed the source. No, not a dead cat or even a dead mouse, but a dead line output transformer. Not just dead, but burnt, melted, black and smelly.

The smell you’ll never forget is the smell of burnt electrical insulation. It’s quite acrid and imprints on your brain forever.

What does this have to do with computers? As a computer technician I encounter many ‘nogo’ faults. The computer simply won’t turn on. This is often a dead power supply. A good indication of a fried power supply is …. You guessed it… ‘The smell you’ll never forget’. Just sniff near the exhaust fan at the back. Not always, but generally that smell indicates cooked components.

A computer power supply normally comes out fairly easily so is an easy component to replace and get a client running again. Once it’s out flipping it upside down often reveals the presence of ‘bits’ floating around inside. That’s bits of destroyed electrical components. These days you just wouldn’t bother to repair a pc power supply. Well, I have been known to replace a fan in several but that’s a different story.

So, when you smell ‘that’ smell, expect problems.

Bastard power supply from hell!!!

Computer Aid Posted on by

I have a few motherboards floating around at any time.

They are useful if I need to make up a cheap second hand PC for a customer. I also happen to have 3 identical motherboards(d865glc), that are also the same as my main system… OK, a pentium 4 system is getting a bit old by todays standards, but it works well for me.

A while ago, I used a d86glc to make a second PC at home.

It worked well for a few months, then I needed to mothball it for a few months.

A few days ago, I needed it again, so I started it up again (it started OK), and left it running updates while I went out for a few hours.

When I came back, the PC was off.

Thats strange.

Anyway, hit the power button, and the lights come on for a few seconds, then go out.

OK, maybe the power supply has had it, so I plug in another PSU, only to see the same symptom: PC starts for a few seconds, then stops.

OK then, the motherboard has died. So I dig up one of my 2 spare (identical) motherboards, and being paranoid, I first connect it to the new power supply thats currently on the bench… It starts OK.

Good, now I swap motherboards, and connect everything up again, start the PC, go to the bios and check the settings.

I’m almost finished adjusting the settings, when the PC suddenly stops… all power is lost.

Hmmm, can I have a faulty motherboard and power supply? Highly unlikely.

Maybe the RAM? I pull out all the RAM, unplug all drives, etc, switch on, and the PC beeps (its saying it wants RAM)… OK, I plugin only 1 stick or RAM, but the PC won’t start.

I swap RAM sticks, and this time the PC starts… aHa, maybe it was just faulty RAM causing startup problems.

OK, back to the bios again… and again, I lose power before I can save any BIOS settings.

Whats going on?

The original motherboard won’t work with the new PSU, so I’m sure the motherboard is stuffed.

But why would the “newer” motherboard also fail?

I try swapping and reseating everything (including CPU), but nothing seems to work.

I sleep on it, and the next day, I decide to try the third motherboard on the bench with the new PSU… it works.

I plug the RAM into a test PC, and do a memtest… the RAM has no faults.

OK, I now plug the 3rd motherboard into the first PSU (thats still in the case). Nothing happens…

Hold on! As my fingers brush past some mobo capacitors, I sense some heat.

Capacitors shouldn’t heat up like that.

I cut all power to the PC, and check the mobo… the wires that go to the 12V, 4-pin plug on the mobo are also quite warm… a lot of components in that area are warm… why?

psu

I decide to test the first PSU… I rig up my multimeter, and I expect to see the typical 5V and 12V, but instead I see values shifting between 100 and 230 Volts !

Maybe I’m having a bad dream… I plug the multimeter into the new PSU, and the voltages are normal… back to the original PSU: more high voltages.

My heart sinks: The semi-faulty power supply just fried 3 motherboards in less than a day.

Damn you, bastard power supply from hell!!!

Dell XPS 720 non-standard motherboard/power supply

Computer Aid Posted on by

Someone asked me to help fix their computer.

It was a Dell XPS 720 (ie a high-end gaming PC), and it would run for a few minutes, and then suddenly switch off.

It seems like a failing power supply, so I think it shouldn’t be difficult to fix…

Once I’m in front of the computer, I see the PC is really large… one of the largest PC cases I’ve ever seen… and its really heavy!

It takes me a while to figure out how to open the case.

Peering inside, I see a computer that looks quite different to any modern PC… hard drives, power supply, motherboard… all laid out in a non-standard way.

Despite the huge case and cables neatly arranged, I still need to take out the hard drives, in order to get a good look at the motherboard.

After figuring out how to remove the hard drives, I then see that the power supply is plugged into the motherboard in 2 different places, using non-standard power connectors.

This is something I’d expect to see in the late 1980’s !

Anyway, I realise there is no way I can replace the power supply at short notice, so I reassemble everything, and give the customer the verdict: Either he (or I) will need to contact Dell, and get the power supply for this model PC (and I suspect it won’t be cheap!).

Dell: why do you do this?

faulty power supply in a H340a case

Computer Aid Posted on by

I had a brumby’s outlet call, as their CCTV PC (with a feed from 4 cameras) would only run a few hours, before switching off.

This sounded like a typical power supply failure, except the PC was difficult to reach, and was coated in a black, soot like muck.

It looked like a slimline “HP” style PC, but it was totally black, and had a bright yellow “lookc” name on it.

After opening it up, I could see it had a non-standard power supply 🙁

I also see that the CPU heatsink and fan are covered in the black muck. Since its a pentium 4 CPU, I figure it needs good airflow (regardless of the state of the PSU), so I give them a good clean.

After that I test the PSU: I short the “start delivering power” pins, and the fan won’t start (and no voltages from any of the connectors).

So I make a note of the PSU model number, and go back to the office to do some research.

It turns out I’m dealing with an AOpen H340a case, and a custom power supply.

I find the PSU model (fsp200-60SAV) is available at a few online stores, and I quickly settle on a unit from techbuy.

Delivery was quick, and I pop over and install the PSU. After that, everything works well.

Storms are good for the computer repair business…

Computer Aid Posted on by

Here in Brisbane (a few weeks ago now…), we had about a week of storms. Most would just pass by, maybe drop some hail, and lots of thunder and lightning.

The storms changed, what was shaping up to be a quiet week, into a busy one.

I replaced about 4 failed power supplies.

One customer had his PC and router fried (covered by insurance)

Another customer had his laptop power supply damaged… Also an insurance job… which is odd, as a laptop power supply should be inexpensive to repair except:

The laptop is an Acer Aspire 1700 (with no battery… it wasn’t even sold with one). This one of the weirdest laptop I’ve seen… Its huge and heavy:

  • A 17″ LCD display
  • A 3.5″ hard drive (ie a normal hard drive)
  • Normal DDR RAM (not the usual SODIMMS)
  • A normal Pentium 4 CPU (not a pentium M or a low-power substitute)
  • A 19V, 8 Amp power “brick”… ie 152 Watt… most store power supplies seem to max out at 120 Watt… and to top it off, the power socket in the laptop is a non-standard shape (a large round metal shield with 4 pins within it (arranged in a square shape)…

Why would any company design such a laptop?

return to cockroach central

Computer Aid Posted on by

Here is a followup to my last cockroach story:

http://computer-aid.com.au/blog/2007/05/15/cockroaches-in-the-power-supply/

Customer calls, saying the power supply I installed about 7 weeks ago has failed…

I’ve got a pretty good idea why it failed, so I’m sure it won’t be a warranty replacement.

When I get there, I can see she (or someone else) had tried to fix the PC… loosely fitting side panels would no longer fit together nicely, the power supply has already been removed, and all the cables plugging into the motherboard had all been unplugged… as well as 4 screws securing the mobo to the case… luckily there were another 4 screws that were not removed.

And of course cockroaches.

Lots of them.

Lots and LOTS!

Last time, there were few inside the case (most were outside). But this time there was a nest in there.

I flip the case over and drop it onto the table (from a height of 1 or 2 cm), but few fall out…

Customer has no insect spray… so I can’t kill them off either.

Most are clustered around semi-enclosed spaces (like the small gap between the back of the parallel port, and a bank of capacitors about 1 cm away.

Anyway, I plug in a new power supply (just the 2 mobo connectors, to be sure it will start, as I don’t know if the PC has been damaged), and the PC fires up. Except it doesn’t boot, since the HDD has been unplugged. So far, so good.

I set about plugging in the HDD, CDROM, front usb. I come unstuck with the front memory card cable… the cables are not labeled, and its difficult to know where the plug goes (and I don’t really want to peek too closely at the mobo… many months ago, I discovered that some cockroaches could fly!… usually towards a flashlight I’m holding!)

I leave the unknown plugs, until I can get a mobo manual (and until the cockroaches are exterminated). I “adjust” the case, so that the panels will fit properly again, Check that windows xp starts correctly, them I’m outta there!

but I must return eventually 🙁

20-pin vs 24-pin power supply and pci-e

Computer Aid Posted on by

With this problem, I eventually decided it was a failing power supply…but now I’m not so sure…

The PC was brand new (meant to be a gaming PC), but when 240V was connected, the power LED would blink, and the PC wouldn’t start. So the seller (a Melb. company) gets me to go their customer and fix it on their behalf (to avoid shipping costs).

After a process of elimination I zeroed in on the power supply.

I removed the 20-pin MOBO connector, shorted the “go to full power” pins (on the 20-pin connector), and the power supply came to life… Hmmm, maybe it isn’t the PSU after all…

This is the 3rd time I’ve seen 20-pin power supplies connected to a 24-pin motherboard. I always feel uncomfortable when I see this.

OK, I plug in the PSU connector to the MOBO again, and the PC started up (for the first time since the customer had taken delivery). I checked out the screen resolution, and after 5 minutes, I declared that the there must have been a bad connection with the 20 pin connector.

I shut down the PC, put the side panel back (it has an exhaust fan, so I plug it in as well), then fire up the PC, but I just get a blinking power led (again)…

I take a guess that the exhaust fan might be causing a problem, but after I unplug it, the PC still won’t start.

OK, it must be a faulty (brand new) power supply… Its probably just on the verge of failing.

I go get another PSU from the car (it has a 24-pin motherboard connector). And by using this PSU, the PC starts first-time, every time.

Good, I swap PSUs, help out with a minor display problem, and I’m on my way again.

Later, I do some research on 24 pin and 20 pin PSUs and MOBOs, and I discover something new (and interesting):

You can plug a 20 pin PSU into a 24 pin MOBO… but it might or might not work. It seems that the extra 4 pins are for some of the more demanding motherboards, and for PCI-e video cards…

Hmm, the customer had a video card (but I’m not sure if it was PCI-e).

So, its possible that the PCI-e card wasn’t getting enough power, and was preventing the whole PC from starting.

I also get to keep what I now realise is a perfectly working, new PSU… Just as well, as the Melb. seller complained about how much I’m charging (they say it should have been a 10 minute job…), and complained about what I charge for my PSU… If I don’t agree to their lower fee, its implied that they won’t pay… So I lose out on $35, but I gain a $75 PSU 🙂

i’d say megapc need to be more careful about how they build pcs.

cockroaches in the power supply

Computer Aid Posted on by

This is probably the worst job job I’ve ever had to do.

Customer say her PC stopped working. Something popped, and there was a burning smell from the PC.

Sounds like a straightforward power supply replacement.

When I get there, the living rooms looks quite sparse… seems like a lower-class house (not that I care about class).

The PC (it looks very new… its just out of warranty) is in the corner of the living room, on a wooden bench with a tablecloth. Customer has broadband internet.

A few quick checks, and I see the power supply needs changing. I go to the car, get a new power supply, and test it to make sure it works. The new PSU works well, so I tell the customer I’ve found the cause, and I can easily fix it..

She asks how much I reckon it will cost in total. I tell her, and she says she will need to go the the auto-teller, to get the cash.

So I’m left alone in the house (with 3 young kids… I suspect they should be in school). It seems a bit odd.

Anyway, I complete the PSU change, start the PC, and notice the keyboard and mouse don’t work. I get my cheap KB and mouse from the car, and can finally login.

Since I’m waiting for the customer to return, I sit down and start checking the antivirus, etc… as the PC seems a bit slow.

I start to notice movement out of the corner of my eye…

Its a cockroach, climbing up the PC speakers.

As I continue working, I notice more of the critters “exploring” the table… Since I’m no longer making a lot of “noise” from changing the PSU, they seem to decide to start exploring… All up, I’d say the table was a host for about 10 or 20 cockies of various sizes… all exploring the PC, speakers, widescreen LCD monitor, etc…

As I work on the PC, I find I need to flick away the ones that get too close to the keyboard or mouse… Now I think I can see why the power supply failed…

My mind starts to play tricks on me: I think I can feel something in my hair… on a few occasions, I imagine something crawling up my pants leg… but there isn’t anything there.

The customer eventually gets back, pays me, and I’m relieved to be out of there.

gecko in the power supply!

Computer Aid Posted on by

Warning: You probably shouldn’t read this, if you have a queasy stomach, or are sensitive to talk about dead creatures.

A few months ago, I came home, and I found the house had no power.

A check of the power meter showed that the earth leakage circuit breaker had tripped. I flicked the switch to reset it. But after a few seconds, it trips again.

By process of elimination, I narrow th problem to an old (pentium 2!) PC in my workshop.

I open up the PC, and I find ants, cockroaches, and geckos… YUCK! I see some yellow stains (that once were liquid).

I brush out all the animal life, spray the ventilation holes with insecticide, and set some cockroach baits around the workshop (which worked very well).

I try the PC again, and it now works fine. I put everything back in its place.

About 2 months later, the same thing happens (no power… the same PC is shorting out).

I open it up again, but this time it looks clean.

I start to dismantle the power supply, thinking its probably dead. As I pry open the PSU case, I see a large gecko inside 😮

I drop the PSU outside, on the grass, and the gecko leaps out.

I then finish taking off the PSU cover, and as I peer inside, I can see a headless gecko body across the 240 volt power terminals :-s

I carefully remove the “short” (REMEMBER: working inside a power supply can be deadly. Don’t do this unless you know what you are doing!). I also carefully look over the rest of the PSU, and I find 2 dead cockroaches (I remove one, the other is inaccessible, so I leave it). I also find the head of the “fried” gecko (at the other end of the PSU!)… Looks like it literally got it head blown off…

Anyway, I reassemble everything, and the PC is working again.

Now, the reason the geckos got into the PSU is: the PSU fan is a “push” fan: Its inside the PC case, and it pushes air through the PSU. Most PSUs use pull fans (the fans pull the air through the PSU, so that the fan is the last device before the air gets outside the PC case).

So, the ventilation holes at the back of the PC/PSU are a little larger than normal, they are rectangular, and there is no fan directly behind them. A perfect home for a wandering “lizard”.

How do I stop this from happening again?

I was thinking extra wires to make the ventilation holes smaller, but it was going to be messy. Then Mandy had a great idea: Use packing tape to totally seal the holes, then poke some holes into the tape. I can now choose how many holes, and their size… perfect!

slight power supply ‘fade’

Computer Aid Posted on by

It always amazes me, that there are so many different ways for a power supply to fail (or in this case, partly fail).

This is a computer I've worked on previously, and at the time, the power supply would behave strangely when it was initially plugged into the wall. Ie, once plugged in, it would take about 15 – 25 seconds before the PC could be started. It seemed like a slow-charging capacitor, but since the PSU didn't cause any other problems, and since it worked well otherwise, I just ignored it.

Since then (about 3 months ago), the PC has started to randomly power off and reset.

So I replace the 500Watt PSU with a 450Watt I carry around as a spare.

Now the PC can start as soon as power is applied to the PSU, & the random resets have gone.

A complete sudden failure is much easier to diagnose than a random, "works 99%" failure.