Saabscene Saab Forum - Saab Technical Information Resource banner

1 - 8 of 8 Posts

·
Registered
Joined
·
44 Posts
Discussion Starter #1
Its my first attempt at one from scratch.

using old case and second hand motherboard/ processor/ram. its a new power supply and ancillaries.

all connected up and I plug in mains to power supply... nothing, zilch, not even a glimmer of a fan wirring anywhere. not even a teeny weeny little light on anything.

so is it going to be a brand new power supply then thats dead ? it's not the cable as I tried that on another device. not even the processor fan starts.

so my question is where do I start testing and if I remove the power supply and connect it to the mains how do I tell if its dead on arrival ? if I connect it to the mains without anything connected to it can I damage it doing that ?

any help appreciated.
 

·
Registered
Joined
·
1,732 Posts
this is always the most difficult to diagnose could be any of the following

a) you havent connected the two pin switch to the correct pins on the motherboard?
b) Switch on the case (not telling the motherboard to tell the PSU to turn on)
c) dead motherboard
d) cabling from the power supply to the motherboard (both the long connector and a 4 pin yellow and black one)
e) the CPU fan is not connected (the motherboard is autosensing and wont power up if the fan isnt there to stop overheating and burning your house down)
f) i have seen on old computers that even a faulty CD drive / hard drive or graphics card would produce this

so best things i can suggest is when its plugged in there is usually a little green / red LED on the motherboard to say its powered is there one and is it lit up?

take out RAM, and Graphics Card if its not built into the motherboard, unplug Hard drive and CD drive etc so you are literally just left with Power Supply, Case, Motherboard (with processor and Fan)

this will be good enough to get it to spin and will give you a bios beeping code to tell you that you don't have any Ram or Graphics Card in

if that works then put in the components one by one and test each stage (i gave up with messing about with old components a few years ago you can buy motherboard, processor and ram for as little as £100 nowadays, but still have to do this sort of testing for work

you cant rule out the power supply itself as i did have a DOA one years ago, but only once
 

·
Registered
Joined
·
1,169 Posts
To eliminate any short circuits etc you are best to set the system up outside the case.

If you get life outside the case then you will have the confidence for the main build.

Take the board out of the case and put it on a suitable cardboard box (eg motherboard box)
Assemble the main components cpu+cooler/fan,memory,graphics -keyboard +mouse.
Attach PSU

It can be handy to have a motherboard speaker or if not its easy to attach one(usually a pin header bottom left)
as this will help diagnose any bios beep codes.

You should be able to start the system and run to bios setup by shorting the two power switch pin contacts
usually bottom left corner of the board(touching with a screwdriver/metal pen).

If you dont get any life then next would be to clear the cmos(with psu off) by either shorting the relevant pins
on the board or removing the onboard battery for say 10mins.

Then try again.........

You can also "jump" your ATX PSU to start the PSU away from the board

Eg

http://www.overclock.net/t/96712/how-to-jump-start-a-power-supply-psu-test-a-power-supply-and-components
 

·
Premium Member
Joined
·
1,327 Posts
Switch mode power supplies aren't ment to be switched on with no load they can go popDoes the motherboard need a 24pin atx connection, 4 pin aux connection or anything other than the old 20pin connection?
When you plug the iec lead into the psu the cpu fan should blip
Like others have said disconnect anything not vital & try outside of case as some motherboards require nylon mounting
 

·
Registered
Joined
·
1,732 Posts
the easiest way to test the power supply is by trying it in another computer if you can get access to one

its a very simple job as haloweenhamster has said you take the side of a known working computer (obviously turned off), unplug the 24pin connector and 4pin, and plug in your PSU's 24pin and 4 pin, then plug in your PSU to the mains and try and start the computer if it works then you know your PSU is fine (there is no need to take the working PSU out of the case to try yours etc) it can just sit on the desk next to it
 

·
Registered
Joined
·
44 Posts
Discussion Starter #7
the easiest way to test the power supply is by trying it in another computer if you can get access to one

its a very simple job as haloweenhamster has said you take the side of a known working computer (obviously turned off), unplug the 24pin connector and 4pin, and plug in your PSU's 24pin and 4 pin, then plug in your PSU to the mains and try and start the computer if it works then you know your PSU is fine (there is no need to take the working PSU out of the case to try yours etc) it can just sit on the desk next to it

well it's a strange one. I connected up the old psu and I had life (well the fan started but nothing else).
so I followed all the suggestions and connected it all up outside the case with the old psu and I got a bleep as there was no graphics card connected . so I tried the new psu in situ and had the same result of bleep !

so I put it all back in the case including the new psu and I got a bleep again :)

so I'm now waiting for some cables to connect the graphics card power as it needs two six pin power supplies from two x 2 four pin ide style power connectors. Stupidly I thought it only needed one four pin to feed each 6 pin power connector adapter.

thanks for all the suggestions :) it's a good learning curve for me :)
 
1 - 8 of 8 Posts
Top