Base unit cleanout disaster!

[Badger_69]

Hi all, i'm a bit of a newbie to forums so sorry if this post sounds a little confusing.

Here goes,
I have just aquired this custom built gaming pc with vents and fans all over the place, its not a top spec machine but does or did the job and is good for a beginner like me.

Anyhow on taking off the side panel of the case i noticed that all the fans and vents were clogged up
with thick dust so i decided to strip it all down and give it a good clean out, but after taking the heatsink and fan off the cpu like most beginners i got most of the thermal compuond on my hands and also upon replacing the power lead to the CPUFAN port i accidently bent the pins.

I bent the pins back into place and fitted the power lead all as it was before but when i pushed the power button to boot up i just got a siren noise from the system speaker and the cpu fan was not active, could anybody give me advice on whether it could be down to the lack of thermal compound now between the heatsink and cpu or does it sound like either the cpu fan or power connection on the mobo could be damaged? Oh also i get code A0 from the motherboard which i can find nothing about.

Here is a list of some hardware etc on the pc if it may help:
ABIT N18 SLI GR (Motherboard)
Pentium 4 LGA 775 3.4GHz processor
Akasa AK-955 heatsink and cpu fan
3 sticks of 512MB corsair value DDR2 ram (was 4 but 1 Died)
PNY technologies GeForce 7600 GT graphics card (SLi ready)

Any help or suggestions on this would be much appreciated as i dont want to go out wasting my hard earned cash if it is just a simple problem.
Thanks in advance.

[SiM]

That is not a gaming pc btw... its pretty old spec...

Try plugging the cpu fan into a case fan connector and then boot. Go into the bios and turn the cpu fan alarm off

[peterb]

The siren noise will be because the CPU fan isn't running, and the System will shut down to prevent the CPU overheating.

If you have removed the CPU from the heatsink, you really need to clean all the old compound off and use new stuff.

To clean off the old, use something like Isopropyl alcohol (available from Maplins) and remove it from both the heatsink and the CPU surface.

Get some replacement compound - there are various makes, and people have their own favourites, to tbh, they are all pretty much of a muchness. Maplin sell some by Akasa - that will be OK.

Follow the instructions with the compund, but in general, apply a VERY small amount - the size of a rice grain, to the CPU, and replace the heat sink - use a slight rotating motion to spread the compund and secure the heatsink. Remember that less is more effective!

As for the fan problem. Check that you haven't broken any of the pins on the mobo. There are three pins used, one is power, one is the speed sensor, and the other is a common connection. You need all three. If the pins have broken off the header plug on the mobo, you will need to get it replaced or replace the mobo. Otherwise check that the plug is connected correctly and try again.

Edit - if the pins have broken, try SiM's suggestion above.

[Badger_69]

I have tried that already SiM, the fan has 4 wires but the other fan connections only have 3 pins and the system will not get to the stage to go into the bios.

[Badger_69]

Thanks peterb for the advice, just one more question for you tho, could the thermal compound stop the fan from operating thus causing the siren to sound or does it sound like i have damaged the actual fan during my cleaning process?
All the pins are still there on the mobo's cpufan port although not as straight as before but the plug does fit into all four pins.
Thanks again.

[peterb]

Lack of thermal compound wouldn't stop the fan from working. It is possible that you have damaged the fan connections (on the plug) pulling the plug off (especially if you used the wires to pull it off )

Difficult to test the fan in isolation - I m slightly surprised that the fan has four wires - I've just checked an older mobo here and the CPU fan has only 3 wires.

[Agent]

http://www.intel.com/support/motherb.../cs-012074.htm

4 pins are starting to get more common now. The 4th pin is PWM (Pulse Width Modulation) which allows much more control over the speed of the fan IIRC

[Badger_69]

I think i will just buy a new fan as i have no way of testing this one due to the fact it has 4 wires and all the other fan connections on my mobo only have 3 pins, just gonna stick to my PS3 for gaming and use the abit system for tinkering around with.

Thanks for all the advice

[Agent]

Just take a 3pin fan and stick it on there to test it - they are perfectly compatible

[peterb]

http://www.intel.com/support/motherb.../cs-012074.htm

4 pins are starting to get more common now. The 4th pin is PWM (Pulse Width Modulation) which allows much more control over the speed of the fan IIRC

So the PWM control circuitry is built into the fan - rather than a separate PWM controller (which I think works with conventional fans)

Sorry - going a bit off topic...

[Agent]

So the PWM control circuitry is built into the fan - rather than a separate PWM controller (which I think works with conventional fans)

Sorry - going a bit off topic...

As I understand it, the PWM circuitry is still on the motherboard. The 4pin fan I have here out of my shuttle certainly has no visible additional circuit (that's not to say its not hidden though).

PWM in this case works by sending a "pulse" - with enough of them, it allows the fan to keep ticking over while offering a higher precision. Varying voltage across a fan is actually a really bad way to control it (PWM = Less waste in voltage, Less needed for same speed etc..)

[Agent]

This explains it better than me, with more technical details

http://www.cpemma.co.uk/pwm.html

[peterb]

Oh yes, I understand the principles OK - its just the implementation in this instance. PWM has been used for a long time in industrial applications (traction motors etc - listen to Jubilee line trains!) as you still get lots of torque at low speeds. However that is less of an issue with something like a fan - but you could get the same effect with a 3 wire fan by controlling the 12V supply with a PWM controller (as the cct in the link you posted shows). With 4 wires, the PWM controller could be built into the fan casing, and controlled externally through the 4th wire. Haven't found much in the way of detail on Google though!

[Badger_69]

Just tried it with a 3 wire fan and all went well, so thankfully it is just a new AK-955 CPU fan im gonna have to buy and not a mobo. Does anyone know if a new heatsink fan comes with thermal compound already on or would it be best to buy some?
Thanks for all the replies peeps!!!

[Agent]

I suspect the problem with doing it with the current 3 pins via PWM is that you run the risk of breaking a lot of current 3pin fans - Many fans have their own internal resister/s, some (but a lot less) a capacitor to help with their initial start up and low voltage operation. I'm not too sure how a PWM square-wave signal would cope with this? (honestly no idea)

[Agent]

Just tried it with a 3 wire fan and all went well, so thankfully it is just a new AK-955 CPU fan im gonna have to buy and not a mobo. Does anyone know if a new heatsink fan comes with thermal compound already on or would it be best to buy some?
Thanks for all the replies peeps!!!

It really depends on the heatsink. Some come with some, others don't.
Just buy some for the sake of a few quid, its not really expensive