computer mother board startup problem

Hello,

I am new to this forum, and doubt if this is the right place for posting it.
I have had some basic knowledge of electronics which is the reason i am posting here.

i am having an asus mother board for amII atholon processor with am3 socket. recently it got shorted or something due to some electrical problem and it being in last stages of warranty i got it repaired. Now since the time i checked it up after it came from warranty at the service shop and assembled it back into my computer i am facing a crazy problem.

i switch on the power to pc
i swithc on the pC (nothing happens)
i switch on any other electrical equipment in the house nearby the socket providing power to pc (Computer starts up like there was nothing wrong)
after i switch off or shutdown if i want to start it again i have to follow the same routine.


i was following the routine till 2 months back. now i am faced with even crazier problem.

i switch on the power to pc
i switch on the pc (nothing happens)
i switch on/off my electric lights, fans, refrigerators and any other damn switch which may start the computer. (only fan and power led lights up no hdd led(nothing else happens do what i may)
i swithc off
i open the case short the jumper, remove and clean the memmory, and start again at no 3 after power down.
if i am lucky computer starts up with bios reset.

Now beacase of my limited knowledge in electronics i doubt it is due to some power surge differenciation the computer starts up. and due to this only the mother board is not working as it should.

If you guys could help, please tell me where should i suspect for the problem, with smps or with motherboard. i have tried replacing ram from other computers and using my ram with other computers which works fine on other computers.

thank you

i don't see anything wrong with motherboard, if there is a surge in power line, it will be filtered out in SMPS and before that in UPS. So, i guess its something to do with power connection in your house. But, lets solve from start to end:
1. connect any other electrical or electronic equipment on the PC socket, is it working? (just test the socket with AC tester as well)
2. If yes, connect the PC to another working socket and test whether the PC repeats its behavior.
3. If yes, then get the SMPS output on any electronic board and do a load testing on it with different resistor and reactive load. If you don't have loader circuit, simply use resistors.
4. If SMPS works fine, connect your SMPS to other PC or your friends PC (motherboard) if possible and check if same thing happen to other motherboard. If yes, then problem with SMPS, or UPS, power supply connection.
5. If not, then problem with motherboard power on and startup circuit or with BIOS is corrupted. Upgrade the BIOS once from manufacturer website and rerun the motherboard. If the problem still persists, send the motherboard back to manufacturer and get it repaired.

Hope that helps.

there were some electrical problems and they were the reason motherboard got fried in the first place. after getting it repaired and having changed sockects and recently changed my house also but the problem is as it is.

Yesterday during my experimentations i again flashed bios, removed keyboard pin(several of my hit or miss experiments) and then tried and the computer started with bios reset (after several tries of on/off procedures). i played age of empires for 4 full hours with no problems and then before going to bed shut down the pc and then again tried to start and facing the same crazy problem.

I will take your advice and check the smps.

thank you for valuable advice

Static charge is one of the things that could create a problem.

Do you put the computer near static-prone items? (Furry animals, old style CRT televisions, newly washed laundry?)

Have you checked with a static detector in the vicinity? A simple one can be made using a JFET and an LED.
See this article:
http://amasci.com/emotor/chargdet.html

Did you try connecting a ground strap?

Is there a chance there is an isolated board inside the computer? One which requires the remedies which you perform, so that its volt level becomes the same as the other boards? This sort of mismatch might be possible if a screw was not tightened when the previous repairs were done.

Static charge is not necessarily a more likely explanation than a quirky power supply.

standard PC SMPSs do not come on unless there is a minimum load on the +5V line. So if your "current" detector is set too high, until you get a little increase in the +5V (which then draws more current), the PSU remains "dead". Do any of the LEDs come on while the PC seems dead?
Frank

the mother board led lights up whenever i switch mains power on to smps indicating that there is current.

I have many a times removed all components connected to computer mother board (like cables, mouse pins, hdds,with basic display connectivity and a keyboard only) and tried to start it. sometimes this is the only procedure to start it (after many days of activity). I have also thought of replacing the cmos battery but i then pefectly remember buying a new one and replacing it at the service center before it was gone service.

One thing i forgot to mention is that keyboard leds always light up initially when to computer tries to self test. the thing is that it dosent go any further.(i deduce the computer has started normally from the fact that after all leds blink only num lock is active on normal startup) and the fact that i have switch on/of my tubelight every now and then is not that big a problem than the fact that this crazy thing starts up only when it wants to. I have had no luck in getting it work since i last posted about its working. i have tried to mannually short startup Pins of motherboard instead of using the powerswitch thinking the switch might be the problem but it is not the case.

Since the board was in warranty i am forced to believe the service center may have updated the bios during the service.

I am firming up on throughly checking up the smps. i will post the result. thank you all for the valuable advice.

Just a simple test, go to your friends home or your neibour house with your PC, and do try to start your PC and check if same crazy thing happens. If yes, change the SMPS and then recheck. If again yes, simply get back to service center for repairing motherboard. If no, then buy a new SMPS, that may solve it. Just do this and check if problem repeats itself irrespective of places.

Hope that helps.