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Thread ID: 131155	2013-04-28 06:06:00	Weird Boot Problem	Billy T (70)	Press F1

Post ID	Timestamp	Content	User
1338638	2013-04-29 03:16:00	I had exactly the same temperature related problem as detailed by wainuitech. The colder the weather it would almost always fail to boot on first try. In my case it would cycle between attempting to start/turn off/start again all by itself. It was quite amusing to watch it do this up to six times or so. On inspecting the PSU it had several bulging capacitors so I knew it was the problem. I replaced the PSU and I've never had a problem since. pressf1.pcworld.co.nz	Rod J (451)
1338639	2013-04-29 03:45:00	I had exactly the same temperature related problem as detailed by wainuitech. The colder the weather it would almost always fail to boot on first try. In my case it would cycle between attempting to start/turn off/start again all by itself. It was quite amusing to watch it do this up to six times or so. On inspecting the PSU it had several bulging capacitors so I knew it was the problem. The marginal\failing capacitors have higher ESR when cold, once they get heated up a bit the ESR drops and things start working again.	Agent_24 (57)
1338640	2013-04-29 04:06:00	Also I've seen this caused by a cell phone left in to charge on a USB port . Flash drives also, USB can cause weird stuff to happen . I also fixed a dell pc with a dodgy psu that would start and run fine the first time you tried but if you shut it down would not start again until unplugged from the wall and left for several minutes . The psu was not suplying voltage to it's fan either . You don't mention if you tried without the UPS as suggested? Try to think what is different between home and the shop and eliminate everything you can 1 by 1	dugimodo (138)
1338641	2013-04-29 04:09:00	Thanks People I have taken on board 100% the peripherals argument and will pursue that line of investigation, it makes good sense to me now . Also, this morning I did some research into booting issues and learned a helluva a lot that I didn't know about boot processes! I remain unconvinced about the power supply though, because I still doubt that it would fail repetitively here over a number of consecutive startup attempts, but start every time over a week at another site . It is not an el-cheapo supply either, being a business computer, I spared no expense in terms of quality components and it has plenty of load capacity headroom . I did this for my previous three computers, which spanned 18 years of reliable daily use and they lasted very well . I am well familiar with bad caps too, having repaired several hundred switchmode supplies over the years, though to be fair, not the computer variety . I know that even good quality caps still fail from time to time, but their failure modes are a little different and not quite so obvious, though some may bulge a little . However, only crap quality or seriously under-rated caps bulge in bulk . I test 'in-circuit' with an ESR meter and that shows up even minor deterioration, long before they become problematic . They bulge because their initial losses (ESR) are higher than normal, so the high frequency ac current they must pass causes internal heating and cooks their electrolyte . This causes their ESR (equivalent series resistance) to rise even further, which causes increased internal dielectic and resistive losses, which in turn generate more heat, which then accelerates the final failure . It is a slippery and exponential slope once it gets started . Cheers Billy 8-{) :thumbs:	Billy T (70)
1338642	2013-04-29 07:24:00	So just try it without the UPS already ... :D	fred_fish (15241)
1338643	2013-04-29 07:58:00	I would rule out a peripheral problem first. I once had a USB device (old webcam, I think) that went faulty and caused all sorts of problems.	Agent_24 (57)
1338644	2013-04-29 10:40:00	So just try it without the UPS already ... :D Nope, it ain't broke. The UPS is fine, as I said before, it is a professional sinewave full time on-line UPS which means that at all times the computer is running off the inverter, not the mains. It is not a cheapie consumer item, and it is highly unlikely to produce those symptoms at random. I have all the gear necessary to verify that, but I'm not going to bother, it runs just fine. I've monitored the output and it is clean as a whistle and stable as the Bank of England used to be (and that is mirrored in the UPS LCD display screen as well). That sort of gear does not throw random temper-tantrums, they either work or they die in a blaze of glory. I just flicked the power off and it didn't miss a beat, just the fan speed increased a little to ensure it stayed cool. I think it is more likely a peripheral problem, and I'll look into that once I've caught up with my work, but at present I wouldn't shut it down for love or money. Cheers Billy 8-{)	Billy T (70)
1338645	2013-04-29 11:11:00	Its actually a very easy fix to find out the problem or at least narrow it down. Once you can shut it down over night, disconnect ALL peripherals, or at least exactly the same as when it was at the shop. If it still fails to boot then its a power feed problem someplace, the UPS may be top of the line equipment but that means bugger all if there's a fault with the power Supply in the case or a circuit on the motherboard. All a good Power supply is doing is supplying good power, once it gets there all that can change. Then again it could be like some problems -- for gods sake what ever is playing up, hurry up and fail completely that'll narrow it down 100% :D	wainuitech (129)
1338646	2013-04-29 22:32:00	Then again it could be like some problems -- for gods sake what ever is playing up, hurry up and fail completely that'll narrow it down 100% :D Got to love intermittent faults! :rolleyes:	Agent_24 (57)
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