Fan Question

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ellinj · #1 Post by **ellinj** » Sat Jan 15, 2005 8:30 pm

I just got a new Thinkpad T42, quick question about the fan, when the fan comes on it seems to go full speed for a second and then slow down. Also, while on it will periodically make a sound almost like a hiccup, I am not sure if it is slowing down for a split second or if it is speeding up but its kind of annoying. I don't really mind that its on I just would like the noise level to be fairly consistently. Ironically enough my old compaq laptop which had a much hotter processor the fan would only come on if the cpu was cranking over 50% or so. This machine the fan always seems to come on after about 1/2hr of usage even if the cpu is only at 4-5%.

steelie69 · #2 Post by **steelie69** » Sat Jan 15, 2005 8:36 pm

it's a bug in the firmware of the t42.

there is no fix.

you can thank IBM's quality control for this one!

thinkker · #3 Post by **thinkker** » Sun Jan 16, 2005 1:07 am

Not only firmware problem.

Sometimes you can settle this problem through an added capacitor (>100uF) in the fan circuit.

geobel · #4 Post by **geobel** » Tue Jan 25, 2005 5:14 pm

thinkker wrote:Not only firmware problem.

Sometimes you can settle this problem through an added capacitor (>100uF) in the fan circuit.

Hi thinkker,
I was thinking about capacitor as well... Have you tried adding capacitor or have you read about such a modification of ThinkPad fan somewhere? It is trivial that capacitor soldered parallel to fan circuit should smoothen the voltage pulse but where did you get >100uF value for capacity? Have you measured the voltage pulse amplitude? Current 30s cycling is not as annoying as 5s cycling but I would not mind to have no cycling at all.

Gosha

thinkpadhk · #5 Post by **thinkpadhk** » Tue Jan 25, 2005 5:40 pm

Gosha,

If you think the measure of a capacitor is referred to as its "capacity", then you have no business going anywhere near a circuit board with a soldering iron. It's called capacitance, by the way.

You can stick on a huge hongking capacitor if you want - the bigger it is, the more stable the dc voltage. However, the bigger your capacitor, the longer it will take for it to charge up to the correct level. My advice... just leave it alone unless you think you know more than the engineers who designed and simulated and tested the thing.

tfan · #6 Post by **tfan** » Tue Jan 25, 2005 8:03 pm

I really doubit if this is a firmware related "bug" (Fan going on full speed when you boot and then slowing down"). I have seen this happening in other Dell laptops too. *I* would reason that this is done because you don't intially know the temperature of the system (could be sitting in a hot car before being booted) and the fan goes on in full speed while the bios gets the reading from the sensor..but again, I could be wrong

Dow Jones · #7 Post by **Dow Jones** » Tue Jan 25, 2005 9:14 pm

thinkpadhk Posted: Tue Jan 25, 2005 3:40 pm Post subject:

--------------------------------------------------------------------------------

Gosha,

If you think the measure of a capacitor is referred to as its "capacity", then you have no business going anywhere near a circuit board with a soldering iron. It's called capacitance, by the way.

Heh, "farads" is the measure of the capacitor's capacitance.

Maybe both of you shouldn't be messing with the circuits.

Don't I sound smart?

geobel · #8 Post by **geobel** » Tue Jan 25, 2005 9:32 pm

thinkpadhk wrote:Gosha,
If you think the measure of a capacitor is referred to as its "capacity", then you have no business going anywhere near a circuit board with a soldering iron. It's called capacitance, by the way.

Thanks for corrections, hk. I am not native speaker and my direct translation of the term appeared to be incorrect. According to http://www.thefreedictionary.com/capacitance the "capacitance" and "capacity" (in particular "electrical capacity") are synonyms so it is quite confusing matter.

thinkpadhk wrote: You can stick on a huge hongking capacitor if you want - the bigger it is, the more stable the dc voltage. However, the bigger your capacitor, the longer it will take for it to charge up to the correct level.

That is why I am interested in the minimal capacitance that would have noticeable effect and asked whether the indicated value was calculated in some way

thinkpadhk wrote: My advice... just leave it alone unless you think you know more than the engineers who designed and simulated and tested the thing.

At the times when fan was cycling every 5 s I was often close to smash my T40 against the wall, thanks to clever engineers. They do know much more than I do, but they are unaware what I can bear and what I cannot. Now, when fan cycles every 30 s the situation is tolerable but I still phlegmatically research on possible improvements. If you check forum archives you will notice that quite a few users expressed their concerns about disturbing fan cycling in quiet environment.

Gosha

thinkpadhk · #9 Post by **thinkpadhk** » Wed Jan 26, 2005 1:41 am

Dow Jones wrote:
Heh, "farads" is the measure of the capacitor's capacitance.

Maybe both of you shouldn't be messing with the circuits.
Don't I sound smart?

Ummm... no. Farad is the UNIT of measurement. But now we're just arguing about grammar.

I hope I can be messing with circuits. I've been an integrated circuit designer for the past 7 years.

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