Motherboard or PSU??

Ok, got this old school computer from a friend and i plan on getting it back online and give it away to someone less fortunate. its about as decent as a windows 98 machine is gonna get. so it will make someone happy. But anyways. they gave it to me broken and when i plut the power cord in, the back switch is set to off. i flip it on and it acts like it wants to power on automatically. the fans spin *cept for the north bridge fan cause i think its dead* and the front lights, including the cdrom just blinksaggressively. and u hear a grinding noise. i want to think motherboard. but they did have a surge so it could be either mobo or psu. any ideas for the sympoms i described? i have NO exess materials to work with and dont plan on buying a replacement until i know what it is. almost forgot. when i press the power button of the front of the pc while its grinding. it then acts like its perfectly turned on. then if i hold it down and turn it off. it goes back to grinding.

 

It sounds like it's the motherboard or the powerswitch (if it works fine when you pushdown on switch), i don't think it's the psu, because if it was it would not powerup at all.

 

As for the grinding noise, have you tried listening for the noise with the case panel off?
Grinding would come from a moving part, i.e. a fan (if you're lucky), Optical drive, or HDD.

 

i did take off the case. its hard to tell. i know the grinding comes from the front. it has 2 hdd, and of course the optical drive. it comes from that vicinity. i listened pretty hard and i believe that it is comming from the master hdd. the slave seems to sound fine. how can i trouble shoot if it may be the power switch? *btw, i noticed some caps on the motherboard to have rust on the top indicating leakage.* its an old ABIT KT7.

 

Logan;
the pwr switch is probally ok
here is what u could try un plug the power plus to all the drives except the slave hd, (un plug the pwr plug to the mstr hd,the cd rom pwr connector at the cdrom, same for the optical drive, etc), and un plug the fan that is not working.
and then try to power it up
with some luck it should start to boot and stop at the bios screen or promt u to enter the bios screen, u can then if it get this far power it down remove the slave and make it the mstr hd and see if it will boot to a screen of course add the unplugged drives one at a time except the mstr hdd by turning it off and rebooting. if all is well u can and u may then need to load the operating system, get a new fan an u have a pc again that works

asturnacle

 

Ok, the grinding is comming from the floppy. i unplugged that. the master and the cd rom. when i turn it on. the fans are all powered up*on the geforce 2 mx* and the NB fan i got the dust from under it and it ended up actually being fine. however when i plug in the power cord and flip the back switch. the front lights *hard drive and power lights* flash aggressively and like i said before the fans power on a lower power level until i hit the power button in the front. this is with just the slave hooked.

 

If you have bust caps on the motherboard, it won't power up properly (or if it does, it'll probably cut out after running a while). I think you're looking at a new mobo, or you could try getting the caps replaced.

 

i figured. noticed one cap went pyramid. but it seemed odd in the scheme of things with the grinding. just wanted to check all possible options before purchasing anything. thank you for your help.

 

it is possible to replace caps, not easy, but possible. just make sure you use the right capitance and don't reverse the polarity or you will have a capsplosion, this is fairly amusing but it wouldn't be good for your computer.use a low heat soldering iron(30w or less is good), not and industrial strength soldering iron for pipes like the one I have, the stupid thing weighs lik 6 pounds, lol.

 

haha. i have that cold head thing on the infomercials. had to get it. works like i dream. i replaced the caps on my old OLD asus. had an athlon 1.4 ghz. surge blew the caps and i replaced em. *im pretty avid with handy things* just wanted to know if a psu would be involved and if not wether or not it was factually the motherboard due to the fact that i dont have extra parts lying around to test things out with. good looking out. although i would like to try out ur 6 lbs soldering iron.... *rubs goatee*....

 

I have seen taht cold heat soldering iron, it loom cool, and isn't it onyl liek $20? if it actually wokrs that well i might pick on up sometime, and this is the beast I was talking about, the other day I was trying to blow up a cap with it by heating it up a lot, didn't work
http://s7.sears.com/is/image/Sears/00954046000?layer=comp&wid=190&hei=190&fmt=jpeg&qlt=75,0&op_sharpen=0&resMode=norm&op_usm=0.5,1.0,0.0,0

 

haha, thats ridiculous! the cold heat bit works like a charm. i dont care much about it "cooling down" in seconds. the precision of it is damned good. small jobs on computer mobo's or sound equipment is phenominal. best 25 bucks ive spent. *on the whole bit* a definite buy. make a small bonfire and throw a handful of caps in it. stand back though

 

lol, i gotta try that sometime, I just need some more electronics to gut, old rados are great, there is so much crap in those things.

 

Logan;

Nice to see a bit of visual inspection and Steeev had it pegged.

but u still are at the heart of the problem, was it age and maybe heat that did in the caps, or is it a power supply that is on the edge and has ac where it sould have dc??
If u have a good volt meter find the form factor for the pc and check all the output voltages from the power supply. U might also check the amount of ac that is at each dc output lead. It should be avery low level. Were u able to get it to boot to a bios screen??

asturnacle

 

If your caps look like the attached link, then you identified a problem.
http://news.com.com/2300-1041-5940552.html
It might just be that some boards were plagued with the problem as noted in the following link.http://www.badcaps.net/ident/

 

Iv seen mobos last years with swollen caps, Its the leaking ones that are bad. Also "cool heat" irons are bad for fine computer PCB work.. Thay use an electric arc to heat up the tip, very bad for vid cards and mobos.