Computer doesn't start on main power but starts on ups back up power

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Hell Hound

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Hi guys,
I had a running computer which was going pretty smooth without any hiccups until the day before yesterday.
My pc doesn't start while my UPS is on electricity power but if I switch off the main power of the UPS and try to start my PC it works.
I even have connected the PSU wire directly to the electriciy board without UPS and it doesn't start.
P.S : my mobo is too old so today I removed the mobo bios battery also and it did not help.

Need help guys
 
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I've never used a standalone voltage stabiliser; in fact, it never occurred to me that "domestic" ones existed - I've only ever seen them in industrial applications. I suppose I've always relied on the built-in Automatic Voltage Regulation function of APC UPSes for my servers and suchlike at home and at work, and just basic surge protectors to look after everything else.

So I can't really give any recommendations. You'll just have to ask around - maybe the technician who diagnosed the voltage problem can recommend a good stabiliser. It's probably not...
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molletts

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It sounds like a problem with the PC's power supply. It's not a symptom I've come across before, though. The output from a UPS running on batteries is not quite the same as actual mains power - it's a close-enough-for-most-things approximation (how close depends on the quality of the UPS). So it is conceivable that a slightly faulty device could work on UPS power but not on mains power.
 
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Hell Hound

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Hi Molletts,
Thanks for your reply buddy.
But I have a doubt that when I'm trying to switch on my PC with UPS active on main power supply, the PC doesn't respond or sometimes responds but then becomes dead after a couple of seconds. Here also the power supply is getting through the UPS and my PC doesn't work. So are you sure this is fully something problematic with the PSU.
my PSU is 2.5 years old and it's Seasonic X-650 KM3.
 
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molletts

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If the mains supply is on, the UPS just passes it through unchanged - it only outputs a different waveform when it's running on batteries and therefore having to create the waveform itself. (Some, generally more expensive, UPSes do run all the time, even when the mains is on, but most only run when needed, i.e. when the power goes off.)

I can't think what else it might be, other than the PSU. Can you borrow a PSU from a friend to try?
 
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Hell Hound

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Hi Molletts,

Today i got one technician in my home to have a look into my UPS.
They confirmed that UPS is ok but they also found that the electricity voltage of my house is 270 volt which is very high.
According to them the voltage range should be 180-230 volt otherwise the UPS will not provide output to my PC and also my PSU will cut the electricity transfer to my PC components.
Do you think whatever they are suggesting is correct?


 
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molletts

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Yes, 270V is very high so maybe the PSU is tripping out. The UPS, of course, would always supply the "right" voltage when it's running on batteries. (180-230V is big range - I'm supposed to get 230V ± 7% and, according to the UPS for my server, it's currently 241.8V.)

Most PSUs are rated for 90-264V or thereabouts. I'm not sure what to suggest, apart from to see if your electricity supply company can make an adjustment to your supply voltage. You might have to find out exactly what voltage range they're supposed to supply, then contact them to say that your supply isn't right. You're paying for it, after all. You could argue that it's dangerous - it is probably quite a bit higher than it should be so theoretically it could cause a fire or something.

A workaround for the PC might be to use a step-down transformer (of the type used to connect 110-120V US equipment to a 220-240V mains supply) to make it about 135V (a bit strange but well within the PSU's operating range) but I'm not sure how the UPS would handle having a big transformer connected to its output when it's on batteries. A custom transformer with a turns ratio of 6:5 would give you about 225V which could go to the input of the UPS, if you can find someone with the expertise to make one (it would probably be expensive, too). Of course, the supply might suddenly go back to normal anyway and you'd have wasted money on a transformer.

Some UPSes will regulate the mains voltage automatically if it goes out of range - my Smart UPS 1000 used to go into "brownout" mode if I had three hotplates and the oven on all at the same time in the kitchen (fortunately quite rare as I'm useless at cooking) because the voltage would "sag". The problem went away when the electricity meter was replaced.

Sorry I can't suggest anything more definite... I'd be interested to know how it works out in the end, though.
Stephen
 
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Hell Hound

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Hey buddy thanks for your detailed reply.. However I am thinking about buying one voltage stabilizer which will provide the correct amount of voltage to my ups.
What do you suggest?
 
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molletts

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I've never used a standalone voltage stabiliser; in fact, it never occurred to me that "domestic" ones existed - I've only ever seen them in industrial applications. I suppose I've always relied on the built-in Automatic Voltage Regulation function of APC UPSes for my servers and suchlike at home and at work, and just basic surge protectors to look after everything else.

So I can't really give any recommendations. You'll just have to ask around - maybe the technician who diagnosed the voltage problem can recommend a good stabiliser. It's probably not the first time he's seen the problem, given that he checked the voltage. (It's never even occurred to me to check the mains voltage - I guess I just take it for granted that it's "right". I do carry a multimeter in my PC toolkit - I'm really an electronics guy - but I don't routinely check the mains supply with it. Maybe I'll add that to my standard checks now, as it's a quick and easy one!)

Stephen
 
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