System Restarts on power fluctuations

[art]

well I have a system (Self Assembled) having intel dual core 2.8 Ghz pro. with asrock 945 based board. whenever there is fluctuation in power or power off the system restarts. system works perfectly when the power is proper or in battery backup. Also the processor heat above normal...idle arnd 45 and with heavy load around >60.
I ve Intex 600va internal UPS. I ve several other systems of similar and different configurations which runs perfectly using the same UPS. I ve swapped the RAM, PSU but in vain...The cabinet (mercury) is well ventilated with a rear fan. When the side panel removed temp. lowers 1-2 C. I m fed up of this problem...kindly help me...

system configuration:
CPU: dual core 2.8Ghz
Mbd: Asrock wolfdale 1333-D667
RAM: 1Gb Hynix
Cabinet with SMPS(450W): Mercury
Hdd: 160Gb Seagate Baracudda (Sata)
DVD writer: LG

[mithun_mrg]

if u have a automatic voltage stabilizer try using it before the ups & see also check the earthing of the point u r using

[art]

Originally Posted by mithun_mrg

if u have a automatic voltage stabilizer try using it before the ups & see also check the earthing of the point u r using

ofcourse i use a stabilizer buddy. You are talking of earthing - ground wire or the neutral one...

[mithun_mrg]

of course the ground one what is the rating of that stabilizer u use please procure one with a voltage range of 130~280 or lesser

[art]

I ve 2 KVA satabilizer 90V-280V

Originally Posted by mithun_mrg

of course the ground one

Does ground wire has anything to do with system restart??? I will check it as I m not sure...

earlier I got suggestion from yahoo answer as follow
"You might have the wrong voltage adapter going to the motherboard. Sometimes the PSU's will have 14 or 16 volts instead of a 12 running to it, and sometimes the motherboards call for awkward numbers of voltage. You'll have to buy a kit that steps up or steps down the wattage to the board itself if that's the case... check it out first before determining that your PSU is bad. Look up the stats for the PSU and for the motherboard itself and see if the numbers match up; in all honesty it sounds as though your motherboard is one of the awkward voltage amounts and the PSU is just spitting out either a higher voltage or a sparatic voltage (Due either to bad connection to the motherboard, or even a lose connection with the video card etc. etc.). Check all the connections as well, if anything is almost all the way connected but not 100% down then it could cause a voltage irregularity."
...getting rigid to fix the problem......swapping in card - cpu then MBD and finally Cabinet, just to pinpoint the problem....what do you guys say

[mithun_mrg]

that stabilizer is more than enough u can always check the voltages of PSU with a digital multimeter
if u swap anything first i recommend to get a good PSU

[jagdish]

how old is your ups if its more than 3 to 4 yrs ups battery has gone weak try to replace your ups battery

[pimpom]

Although there are other possible reasons, the first suspect is the PSU (SMPS). A good PSU should store enough energy to keep the computer going during a brief power loss such as when the UPS is switching from mains to battery power.

[d6bmg]

@OP: post the name & model of PSU that you are using.

[pimpom]

Originally Posted by d6bmg

@OP: post the name & model of PSU that you are using.

He's already posted that in his configuration. It's a Mercury 450W bundled with the cabinet.

[art]

Thank you all guys for replying...
The battery of the UPS is perfect as other system runs perfectly. Even when I connect the same PSU with other system there isn't any problem. So every swapping and test points towards the MBD and CPU as the culprit....I think that the MBD is taking more than normal power as the fan's speed is somewhat more.....
can anybody tell me which capacitor(s) are responsible for feeding power during powerouts. Are those two big ones??? I am thinking of putting capacitors of higher capacitance so that the PSU holds more power and for more time.