homemade computer

[sciencenerd]

I have a homemade computer that has a motherboard, modem and internet card, graphics card ,ram and a amd athalon cpu.I plugged it in to a 300 watt power supply and turned it on. It turned on for a few seconds and then turned off by itself. Can anyone help me on what the problem is and how to fix it ?

 

[mvs sarma]

It is tough to offer advise without knowing your tech background.
most computers fail likewise when the CPU gets hot

check whether you have the CPU mounted and the cooler heat-sink with a fan is mounted as per specification.
I feel they use some sort of thermally conductive white paste on the surface before fixing the heat-sink.

 

[dumpsterdiver]

Since modern ATX pc's have standby power you MUST pull the power cord before removing or inserting any parts. If after you checkout the CPU heatsink it still shuts down then remove all cards and ram, disconnect data and power from ALL drives and anything else leaving ONLY the power supply and the power switch connected and see if it still shuts down. If it does not shut down you will get error beeps complaining about no ram. Now put the video card and connect a monitor and see if it shuts down. Continue this process one card at a time. If you get through all the cards then reconnect drives one at a time until you get a shutdown-that card or drive is causing the problem.

 

[mvs sarma]

Asuming that the user is not experienced, I suggest following method ,

before removing or reinserting the cards or ram
one has to SWITCH OFF power, otherwise things would get damaged due to experimentation
So, any insertion of extraction of cards
modules ONLY when PWER IS OFF.

 

[Birdman Adam]

Before touching anything you should discharge any static electricity you are carrying by touching a bare grounded metal surface like on of the case panels, or the case of the PSU. You should do this periodically while you are working.

 

[Reloadron]

I have a homemade computer that has a motherboard, graphics card ,ram and a cpu.I plugged it in to a 300 watt power supply and turned it on. It turned on for a few seconds and then turned off by itself. Can anyone help me on what the problem is and how to fix it ?

Did this system ever run with the PSU you are using it with now?

Generally when a PSU gets a PWR_ON command it will power up. However, if the PSU senses a load exceeding its limits it will shut down immediately. This generally happens in about 1/2 second.

When it tyies to start does the CPU cooling fan and other fans spin up at all momentarily?

If this is a system you added a PSU to you are absolutely sure the PSU is correctly connected and that if this motherboard has aux CPU power (ATX12V2) that power is connected?

Motherboard model?
PSU Model?
How many pins on the motherboard main PSU connector as in 20 or 24?

Ron

 

[binesheb]

there are lots of possibilities which prevent the booting up of a pc.

Can You turn the pc ON immediately after it goes OFF? if yes then you can be sure that the power supply is working fine..

if not then it may be due to two major reason
1)Overheated processor....in this case
check whether the CPU fan is rotating,if yes try removing the processor and placing it back..(be sure that you applied the thermal paste(a.k.a Heat sink Compound) between the processor and the Heat sink. its cheap and available in any electronics parts shop.
2)Overloaded Power Supply...Inn this case remove your graphics card and check whether the problem persist while booting.. if the problem dissapears then you really have to buy a new POWER SUPPLY UNIT(PSU).. Check the graphics card manual for the POWER Supply rating required..Usually Dedicated Graphics card require 500W for good performance..


post with your computer specification so that i can help you better,,

 

[sciencenerd]

The heatsink for the cpu is one that is smaller than the one used before.The cpu is an amd athalon so it gets quite hot. when I turned it on it ran for like 3 seconds then shut down.I don't think it is a psu overload. Can you provide any other information


Yours Truly Sciencenerd

 

[sciencenerd]

No it used to run with a 450 watt psu. I don't think that is is a psu overload because I can turn it on for over 2 seconds.




Yours Truly Sciencenerd

 

[mvs sarma]

presumably the thermal conductivity is lacking
check after applying the heat sink compound

 

[Reloadron]

I would do as mentioned. Carefully remove the CPU HSF (Heat Sink Fan Assembly) and thoroughly clean the heat sink and CPU mating surface with isopropanol alcohol. A coffee filter makes for a good lint free rag. Remove all the old heat sink compound carefully. Oh yes, make sure you carefully remove the HSF assembly too! Then reapply some thermal compound according to directions, you only use a tiny amount and apply exactly as the directions tell you to.

Then try the system again. If the problem persist we can look elsewhere. You need to start somewhere so may as well be the CPU heat sink.

Ron

 

[mvs sarma]

perhaps before cleaning off the heat-sink compound, he must ensure that he has stock of fresh compound.

 

[Reloadron]

perhaps before cleaning off the heat-sink compound, he must ensure that he has stock of fresh compound.

Uh yeah, I would assume he is that far ahead on the curve.

The biggest problem I have seen with the application of heat sink compound or TIM (Thermal Interface Material) whatever we want to call it is that people tend to gob the stuff on the mating surfaces. If the face of the heat sink and the face of the mating processor had an absolutely perfect micro-finish there would not even be a need for the compound. The application of too much is as bad as none at all and every package of the stuff carries with it application instructions that people tend to overlook. The same application instructions vary from manufacturer to manufacturer.

Anyway, this is just the first step but it can't hurt to reapply fresh compound.

Ron

 

[mvs sarma]

one has to smear just a small qty, it would improve thermal eff , as otherwise with the heat on, the surfaces may get oxidized. Yes, the way of application should be meaningful and not in lumps.

 

[tvtech]

The whole idea of "thermal paste" is to provide a way for "hot components" to keep cool. Thermal paste fills in the gaps between the component and the heatsink it is is attached to. The thinner the layer the better. A lot of people canno't comprehend this very simple principle.

So difficult to explain....

More thermal paste applied does not solve problems. It's about giving the best heat transfer between component and heatsink it is attached to.

Get it ??

Cheers

 

[sania92]

Recently I also mad a computer at home, great experience.

 

[dumpsterdiver]

After reading the other posts it sounds like a CPU overheat. I had an experience with a Dell Dimension 4500 regarding that. It was a dumpster find and I did a thourough disassembly and cleanup of everything. When I put it back together I did not seat the plastic "nails" that attach the heatsink support frame to the motherboard. The nails kept the heatsink from sitting on the processor where the thermal grease could do its job. When cold it would run for a minute and 40 seconds and then shut down. When hot-30 seconds. I took the heatsink off, discovered the unflush nails and seated them. It now runs normally.
Are you using the right kind of heatsink and fan? If you can borrow a know good power supply for a substitution test. If it still shuts down then the motherboard or a card is the problem.

 

[TimK]

First I am not convinced it is a heat problem, After all a few seconds is a lot less than the 30 or more seconds that it takes for a cpu to overheat. If the machine was running before and all that was changed was the Power supply then I would focus on it.

This may be a dumb suggestion, but check to see if the Power Supply has a 120/220 switch. If it does and is in 220 v mode the fans may come on for a second and shut off.

Also check to make sure a screw or something did not fall into the case and get lodged somewhere causing a short.

But it's a completely different story If the machine did not run or quit running with the old power supply. Then I would try removing everything and re-installing them one at a time as mentioned earlier.

HTH

 

[spicydeath82]

i had an issue like this with my computer after i upgraded my video card. whenever the resolution changed the computer would shut off. could be your lacking in the power department would be my bet.

 

[shokjok]

Is the computer placed in a restricted setting? Is it on the floor vertically, too close to a wall or heat vent? Is it on a desktop in direct sun for a short time?
Computers are wonderful appliances, but like us they have a limited working environment. If you are downgrading from a 450W PSU to a 300W PSU, you will get the results you are describing.