My PC won't power up properly

  • Thread starter Thread starter Nigel Andrews
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Nigel Andrews

I leave my PC on continuously because of this problem, but when I have to
turn it off then it is difficult to start.

When I turn on my PC it makes as if to start (CPU and case fan jump) but
immediately stops. Then the start button does nothing unless I hold it in
for a period and when I release it then the PC does the same start/stop
again.

I have checked that the PSU fan runs by removing the multi-connector from
the m/board and connecting across green and black in the plug. The fan runs
albeit hesitantly and sometimes it needs a nudge to get it moving. So I
assume the PSU is working OK - just with a sticky fan.
When I reconnect the multiconnector I get one of a number of situations
a) The green light on the m/board comes on and the CPU and case fans move
slightly
b) The green light comes on and the CPU and case fans run for a few seconds
and stop. The discs seem to start to spin up aswell.
c) The above occurs and keeps on running but as I push the multiconnector
fully home it all stops again!
d) The above occurs and keeps running even once the connector is in
I have in the past percevered and got to the last situation where it all
started and ran. But I have tried so many times, this time, and am only
getting the first three conditions.

Could anyone please suggest why this is?

Nigel
P.S. I have had problems for some while with a CD tray ejecting at random
times even when the CD drive was not being used. With the above problem the
CD tray often ejects or retracts just before the power-up fails.
 
Nigel said:
I leave my PC on continuously because of this problem, but when I have to
turn it off then it is difficult to start.

When I turn on my PC it makes as if to start (CPU and case fan jump) but
immediately stops. Then the start button does nothing unless I hold it in
for a period and when I release it then the PC does the same start/stop
again.

I have checked that the PSU fan runs by removing the multi-connector from
the m/board and connecting across green and black in the plug. The fan runs
albeit hesitantly and sometimes it needs a nudge to get it moving. So I
assume the PSU is working OK - just with a sticky fan.
Click to expand...

This part bothers me. Some power supplies detect the current drawn by
the PS fan and shut down if absent, and if it is at all hesitant in
starting, it could be your problem. Does the fan move freely when you
move it with your finger while power is off?

Jumpering the connector as you have done should cause the fan to
immediately start I would think. The fact that it runs once started
might be due to the fan loosening up once it has warmed up the bearings.
 
Ken,

Thanks for your reply.
The PC is a few years old, hence the reluctant PSU fan, and was one of the
first 1Ghz PC's. The fan spins OK without power and when jumpering the
green/black it may need a nudge to get it moving, which it does tho' never
at the highest speed. It sometimes pauses or needs another nudge.
Do you think a PC of this age would sense the PSU fan?
I'll try and see if I can spin the fan when I connect the multi-connector to
try to rule that one out.

Update.
I tried nudging the PSU fan, when after connecting the multi-connector and
the PC seemed to be starting up. Sometimes it ran well sometimes
reluctantly. But it didn't seem to affect how long the CPU and case fans
ran.

I have mentioned the CD tray ejecting or retracting whenever the PC does
seem to be starting. When it does everything stops very shortly after and I
wonder if that is related - draining too much from a failing PSU maybe?


Nigel
 
Nigel said:
Ken,

Thanks for your reply.
The PC is a few years old, hence the reluctant PSU fan, and was one of the
first 1Ghz PC's. The fan spins OK without power and when jumpering the
green/black it may need a nudge to get it moving, which it does tho' never
at the highest speed. It sometimes pauses or needs another nudge.
Do you think a PC of this age would sense the PSU fan?
Click to expand...

My guess is that it is NOT the PC that is shutting down the PS, but the
PS itself. Many PS's have circuitry that sense if its fan is running
properly. (some MBs also have such circuit) This is because the PS
will destroy itself if it gets too hot. If it does not sense the fan
running at a high enough speed, the PS shuts down. From your comments,
it sounds like your PS is the problem. Once it is functioning properly,
your PC might work just fine.

The simplest solution would be to try another PS. Since you say the
fan moves freely when moved with your finger, oiling the fan bearing
might not help. Then again it might? One thing is sure, there should
not be any need to push start the fan on the PS when it is turned on.
 
Ken,

I appreciate your thoughts and understand the logiic. I am surprised that
the fan can be sensed at all but especially as far as it's speed goes. I
will take the PSU out tomorrow and see if I can make the fan run freeer, but
it has dine many hours now so perhaps a new fan (or new PSU) is needed.
When I jumper across green and black the fan runs hesitantly at first and
then speeds up, but even then might stop or at least slow briefly.
Thanks all

Nigel
 
Ken,

I have removed the fan from the PSU and it is qute sticky. It won't spin
more than when I am pushing it.
I carefully applied some spray on penetrating oil and spun it, then applied
power and got it moving, but it was fairly hesitant.
So I am planning to get another fan and try that.
Curiously if I get the fan to spin (jumpering green and black) to the point
where it will start without me pushing it. Then when I immediately try
connecting the multiconnector and get the CPU and case fan to start the PSU
fan once again is very slow to start or doesn't move at all! It's almost as
if there is no power left to move the PSU fan once the others, harddisks etc
are running.
Thanks for your continued interest and support
Nigel
 
Ken,

I have an old PC with a matching 12v fan in it's PSU so I swapped it with
the sticky one.
The result is that when I jumper the green and black the 'new' fan spins
well on it's own and also the disks seem to spin up as befeore. But if I
connect the multiconnector the CPU and case fans barely twitch and sometimes
do nothng! So I have made one step forward and also taken one step
backwards!
I suppose the PSU itself could be faulty (as I suggested before) but I can't
swap in this 'new' PSU as it doesn't have one of the disk power leads long
enough (though I can buy an extender).
I wonder if this new situation gives you any new ideas?

Thanks again

Nigel
P.S. I have also tried turning it on the normal way, but as before nothing
happens unless I hold the power button in for a seconds. Then sometimes the
two fans will twitch but nothing more.
 
Ken,

I find that I can get a 400w PSU locally for £17 (U.K.) (about $26 American)
so perhaps I really shouldn't be messing around.
If it's not that then at least I have a good PSU and will have taken that
item out of the problem.

Nigel
 
Nigel said:
Ken,

I have an old PC with a matching 12v fan in it's PSU so I swapped it with
the sticky one.
The result is that when I jumper the green and black the 'new' fan spins
well on it's own and also the disks seem to spin up as befeore. But if I
connect the multiconnector the CPU and case fans barely twitch and sometimes
do nothng! So I have made one step forward and also taken one step
backwards!
I suppose the PSU itself could be faulty (as I suggested before) but I can't
swap in this 'new' PSU as it doesn't have one of the disk power leads long
enough (though I can buy an extender).
I wonder if this new situation gives you any new ideas?

Thanks again

Nigel
Click to expand...

It sounds like you MIGHT have solved the fan problem, but you need to
trace back your actions with regard to the wiring to the PS. First
attach ONLY the 20 pin connector to the MB and any other MB associated
connectors. This would include the CPU fan if it is not obtaining its
power from the MB. Leaving off ALL connectors to such devices such as
hard drives, CDRoms, and floppy disk drives would eliminate them as
possible reasons for failing to power up. It is easy to overlook
actions you took when you are anxious to solve a problem. One common
error is to attach the IDE cable reversed. This shorts out the data bus
and normally prevents the MB from booting.
P.S. I have also tried turning it on the normal way, but as before nothing
happens unless I hold the power button in for a seconds. Then sometimes the
two fans will twitch but nothing more.
Click to expand...
The "Twitch" you describe is can be due to too much current being drawn
due to a failed piece of hardware, or due to a reversed power lead. It
can also be due to insufficient load current being drawn by the PS.
Since most MBs would draw sufficient current by themselves, I would lean
toward the prior fault.

Also, the MB has circuitry to detect the running of the CPU fan. If no
current is sensed, the PS will be shut down by the MB. It goes without
saying that the PS wattage must be sufficient for your CPU or this fact
too will shut down the PS.
 
Ken said:
It sounds like you MIGHT have solved the fan problem, but you need to
trace back your actions with regard to the wiring to the PS. First
attach ONLY the 20 pin connector to the MB and any other MB associated
connectors. This would include the CPU fan if it is not obtaining its
power from the MB. Leaving off ALL connectors to such devices such as
hard drives, CDRoms, and floppy disk drives would eliminate them as
possible reasons for failing to power up. It is easy to overlook
actions you took when you are anxious to solve a problem. One common
error is to attach the IDE cable reversed. This shorts out the data bus
and normally prevents the MB from booting.

The "Twitch" you describe is can be due to too much current being drawn
due to a failed piece of hardware, or due to a reversed power lead. It
can also be due to insufficient load current being drawn by the PS.
Since most MBs would draw sufficient current by themselves, I would lean
toward the prior fault.

Also, the MB has circuitry to detect the running of the CPU fan. If no
current is sensed, the PS will be shut down by the MB. It goes without
saying that the PS wattage must be sufficient for your CPU or this fact
too will shut down the PS.
Click to expand...
 
Ken,

Thanks for your last detailed info. Perhaps I should have said that I was
able to 'cheat' and leave all the connections from the PS inplace (except
the multiconnector) whilst I opened the PS and swapped the muffin fan. So I
think I was right to expect things to work as before.
Based on the situation and the fact of a new PS being fairly cheap I am off
just now to buy one.
If it doesn't make the PC work then at least I have ruled out one cause and
have a brand new PS.

Thanks
Nigel
 
SUCCESS!!

Then new PS works a treat and even makes the PC power up properly from the
normal push button, which it hasn't done for a long time.
Thanks for your help and advice which, even tho' I chose to go for a new PS,
was reassured by the help you gave.

Thanks again and good wishes.

Nigel
 
Nigel said:
SUCCESS!!

Then new PS works a treat and even makes the PC power up properly from the
normal push button, which it hasn't done for a long time.
Thanks for your help and advice which, even tho' I chose to go for a new PS,
was reassured by the help you gave.

Thanks again and good wishes.

Nigel
Click to expand...

Glad to have been able to help. Happiness is a WORKING computer.

Ken
 
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