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Author Topic: Suspected PC Power Supply Unit problem Leo Enticknap Film God Posts: 7474 From: Loma Linda, CA Registered: Jul 2000 posted 04-28-2013 10:15 AM                        Fresh from my triumph in resurrecting an ailing Honda Civic, I'd appreciate F-T's collective wisdom on a computer problem. I usually leave the mains power to my home PC off when I'm not using it (paranoid about fire risk and standby electricity usage). About 2-3 days ago, when I turned the power supply switch on the back of the PC case on, the motherboard on button wouldn't work thereafter. The HDD light flashed briefly, then nothing. After a process of trial and error, I established that it is necessary to leave the mains supply to the PSU on for 10-15 minutes before trying to start the computer, after which it would start and boot up without complaining. This has persisted ever since. From a combination of guesswork and Google, I suspect that the cause of this fault lies either within the PSU, or a dying capacitor on the motherboard, or a dead BIOS battery. I've replaced the BIOS battery, and that didn't fix it. I'm in a bit of a dilemma about what to do about this. I work from home quite a bit, and therefore need the PC to be reliable. Last night I didn't switch off the mains supply to the PSU, and the computer started without a fight this morning. I'm reluctant to just get a new PSU, because if the problem turns out to be on the motherboard, that's £100 or so wasted (the machine has three optical drives, a power-hungry graphics card and five HDDs in it, and so I'd need at least a 750w PSU). However, an argument in favour of doing that is that the current PSU will only accept a 220-250v AC input, and I might be emigrating to California in the next 12-24 months (my American fiancee and I are getting married around Christmas, and we haven't yet decided whether she's coming to England or me to the US): in that case and if I bring the computer over, it'll need a new PSU to run on an American mains supply anyway. In that scenario, and if the PSU is the culprit, replacing it with an all voltage one would not be money wasted. The motherboard (Abit AB9 Pro3) is six years old now (I built this PC in August 2007), and so it really isn't worth trying to faff around with it down to soldering iron level. I've been starting to think that I'm approaching new computer time for a year or so now, but putting it off because if it is me that emigrates, there's no point in paying to ship a computer across the Atlantic: in that scenario, I'd struggle on with this one until the time comes, donate it to charity and then build a new one after I've moved. I just wondered if anyone has experienced this before and established for definite that the PSU is the culprit. If so I think I'll take a flyer and replace it: if not I think I'll continue with the workaround of leaving it powered up until I know whether I'm going to be emigrating or not. Many thanks in advance.  |  IP: Logged Sean McKinnon Phenomenal Film Handler Posts: 1712 From: Peabody Massachusetts Registered: Sep 2000 posted 04-28-2013 10:42 AM                        Disclaimer: This is just a guess... Seems to me that you have a bad capacitor in the power supply when you leave the main switch on this cap stays charged when you disconnect it overnight the charge drains from it and it is not building up quick enough when you turn it on. I would either replace the power supply or take it for repair but most likely it won't be cost effective to repair.  |  IP: Logged Dave Macaulay Film God Posts: 2321 From: Toronto, Canada Registered: Apr 2001 posted 04-28-2013 12:22 PM                     I would leave it unplugged overnight, power on (and have it fail to boot) then measure the PS voltages. It's easy to poke meter leads into the PS connector plug on the motherboard (push in past wire). If the voltages are all within spec then the PS is OK. Maybe you will only have standby 5v power though. In that case, once again it could either be the PS or motherboard. But since the disk drive light flashes, it sounds like at least some main power is coming on. The pinout is here http://2.bp.blogspot.com/-SUist6hbSN4/Te1VRZRpcpI/AAAAAAAADCY/1VFqNipqtIo/s800/ATX%2BPOWER%2BSUPPLY%2BPINOUT.jpg or lots of other places.  |  IP: Logged Louis Bornwasser Film God Posts: 4441 From: prospect ky usa Registered: Mar 2005 posted 04-28-2013 12:35 PM                        Frys or Mouser should provide an inexpensive new power supply. Louis  |  IP: Logged Frank Cox Film God Posts: 2234 From: Melville Saskatchewan Canada Registered: Apr 2011 posted 04-28-2013 02:05 PM                         |  IP: Logged Marco Giustini Film God Posts: 2713 From: Reading, UK Registered: Nov 2007 posted 04-28-2013 04:48 PM                     PC power supplies are usually so cramped inside it could be tough to replace a capacitor. However, I would not buy a cheap PSU for my computer. Can you borrow a PSU from someone before buying a new one? It's a quick test after all. You can test the rails, but make sure you are doing it while the MB is connected, sometimes this kind of issues are only showing up under a load.  |  IP: Logged Monte L Fullmer Film God Posts: 8367 From: Nampa, Idaho, USA Registered: Nov 2004 posted 04-28-2013 05:55 PM                     Yep, one cap shorted out causing an overload on the other cap for that cap to take a dump on the bridge network. Open up the PS and you might see that one cap with the top all swollen up. Those crease lines that are stamped on top of the cap are actually pressure release points so the cap can relieve the expansion instead of exploding all over creation.  |  IP: Logged Leo Enticknap Film God Posts: 7474 From: Loma Linda, CA Registered: Jul 2000 posted 04-29-2013 03:44 AM                        Many thanks everyone. Agreed that the gremlin has to be in the PSU - left it with mains power on overnight and tried running the computer just before leaving for work, and it started first time without any argument. If there was a fault on the motherboard I can't see how that would be happening, or how the computer would be running completely reliably, with no freezing, BSODs or anything of that sort, once it has actually booted. Working at home on Thursday and will have a look inside the PSU then. Thanks again.  |  IP: Logged Scott Norwood Film God Posts: 8146 From: Boston, MA. USA (1774.21 miles northeast of Dallas) Registered: Jun 99 posted 04-29-2013 07:18 AM                        Agreed with the "don't buy cheap power supplies" comment. Borrow one and confirm that the problem is in the power supply. Unless it is new enough to be under warranty, there are other components that may fail soon in the power supply, so it's probably best just to replace it. The bad thing about power supplies is that failure can kill other parts of the computer as well. If you opt to replace it, look for power supplies in the $100 range (unless you need more power for high-end graphics or something like that). Last I checked, Seasonic was considered to be among the best of the power-supply manufacturers; they make their own units and OEM some models for other companies as well.  |  IP: Logged Scott Jentsch Phenomenal Film Handler Posts: 1061 From: New Berlin, WI, USA Registered: Apr 2003 posted 04-29-2013 12:22 PM                        I'm all for not spending money when you don't have to, but in your situation, I would buy a replacement power supply. The problem you describe certainly sounds like the PS is the issue, and swapping it out is the easiest thing to try with highest likelihood of success. If it turns out that the PS isn't your issue, you'll at least have a backup PS in case of future problems (as a measure, think about how inconvenienced you would be if the PS does give out and the time it would take to get a replacement). When it comes time to build a new PC, you now have a power supply already purchased! I would second the recommendation for Seasonic power supplies. I have several Antec supplies, and I believe they are made by Seasonic. You can get really quiet ones and energy efficient models as well. I think that would be $100 well-spent.  |  IP: Logged Leo Enticknap Film God Posts: 7474 From: Loma Linda, CA Registered: Jul 2000 posted 04-29-2013 01:24 PM                        Agreed completely, so much so that I've just ordered one. Reflecting on this, there have been two or three times in the last few months when the computer has frozen for a couple of moments, and then a taskbar balloon came up saying 'Windows has recovered from a graphics card crash'. This has usually been when I've been doing something power hungry, like rendering edited HD video, with all four cores of the Core 2 Quad processor running at near 100%. I'm wondering if that was an early sign of the PSU being on the way out, or just that it isn't powerful to run the computer comfortably. The faulty one is a 750w supply, so I'm replacing it with an 850w one to see if that improves stability. It'll also accept any input voltage from 110-250v, so if I do end up exporting the computer, all I'll need is an IEC lead with a US plug on the end, and it should be good to go. The fact that the existing PSU has been left powered down for several weeks at a time quite often during the nearly six years it's been running probably hasn't helped it, either. I just don't like the fire risk of it being powered up when I'm not in. Probably extreme paranoia on my part, I know.  |  IP: Logged Leo Enticknap Film God Posts: 7474 From: Loma Linda, CA Registered: Jul 2000 posted 04-30-2013 03:45 PM                        I think I've confirmed that it's the power supply. It wouldn't start at all this evening (even after leaving it on for 15 minutes or so), and so therefore I decided to get the old PSU out of the case, so that I'd be up and running more quickly when the new one arrived (writing this from laptop). As you can see, getting the PSU out meant removing the processor heatsink and fan. It was a good job that it did, because I made a rather gruesome discovery... Gross! All that crap in the heatsink must have been making the fan have to work very hard, and can't have helped the power drain generally. So before stripping the rest of the power connectors and the PSU out of the case, the heatsink and fan got a thorough going over with air duster and an isopropanol-soaked cloth. I also removed the thermal paste from the heatsink and processor, and will be replacing that when the time comes to reassemble. Finally, once I'd got the PSU out, I opened it up, and think I found the deceased capacitor. It's slightly swollen compared to the other one, and there is white goo oozing out of it at the top. Just a question of waiting for the new unit now (and thoroughly cleaning everything else in the meantime)...  |  IP: Logged Marco Giustini Film God Posts: 2713 From: Reading, UK Registered: Nov 2007 posted 05-05-2013 06:01 PM                     I would definitely NOT put a cheap PSU in a system with 7 drives! quote: Leo Enticknap The faulty one is a 750w supply, so I'm replacing it with an 850w one to see if that improves stability Also, keep in mind that a 850W is not necessarily better than a 750W. Again it depends on the quality of the PSU. You can find cheap 1000W PSU on the market but try to squeeze 1000W out of them, or to use them heavily and pray that when they fail they do not bring all your drives and MB with them... As suggested, look for a good brand, and be suspicious of any very cheap PSU.  |  IP: Logged Monte L Fullmer Film God Posts: 8367 From: Nampa, Idaho, USA Registered: Nov 2004 posted 05-05-2013 06:11 PM                     Once every 6 months, a good blast from canned air, or similar to rid of all the dust in the PS and anything else needing force air cooling.  |  IP: Logged Leo Enticknap Film God Posts: 7474 From: Loma Linda, CA Registered: Jul 2000 posted 05-07-2013 08:41 AM                        New PSU in, writing this from rehabilitated computer and heaving a sigh of relief! Thankfully, the old one does not appear to have taken the motherboard, cards or any of the HDDs with it to the electronics museum in the sky, so I think I got away with that one. Monte - OK, I've learnt my lesson! On this occasion I actually did more than just the compressed air spray, and wiped each individual blade of all six fans in the machine with a cloth doused in isopropanol. The processor heatsink's gills got a going over with a pastry brush, too. All the dust and crud is very much out of it now. Agreed completely - a complete, thorough dust and crud removal exercise is something that needs to be done every few months. It clearly brings benefits - the processor temperature is now hovering at around 35 degrees (celsius) while idle: before the PSU failure, it was in the low 40s. Marco - point taken. The PSU I bought was not the cheapest, but not the most stupidly expensive either. It cost £63, which, from looking online, seems to be about the mid point for an 850w unit. The good reviews outnumbered the bad ones by about 2-1, and while I do sometimes run the processor and the GPU up to their limit (mainly while rendering blu-ray images), I don't do overclocking, World of Wankcraft or any of that sort of stuff and the PC case is well ventilated, and so I'm crossing my fingers and hope that I'll be OK.  |  IP: Logged

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