Diehard4700
1 Nickel

Dimension 4700 Post CPU Upgrade Fan Noise

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Hi,

My Dimension 4700 desktop came with a Pentium 4 530 and I recently upgraded the CPU to a Pentium 4 660 SL7Z5 ($20 - Thanks eBay!).  Per instructions, I applied about a rice sized amount of Arctic Silver 5 in the middle of the newly installed CPU and a similar amount on the copper heat sink.  For the first week everything was grand.  Ran some tests to confirm CPU performance and, most importantly (and surprisingly), was able to stream netflix HD movies with minimal fan noise.

Subsequent to that first week, however, some familiar problems returned.  The case fan (connected to the heat sink via a green shroud; which I understand to be linked to the CPU temperature) is loud again and netflix HD movies will not stream smoothly (SD has always streamed fine).  Arctic Silver states that its compound requires 200 hours and several off/on cycles to drop the temp 5% C but I am skeptical that enduring 200 hours of "leaf blower" fan noise will cause this problem to disappear.  I was able to control the fan noise before by eliminating the antivirus program (I use other PCs for general internet and this one connects via a router) and by the actions mentioned below.  I use this machine as an HTPC and it plays music, DVDs, and SD Netflix fine so I am reluctant to toss it - particularly after the favorable, initial CPU upgrade experience.

I've read many posts on Dell fan noise and, accordingly, have:  cleaned the machine thoroughly, added a fan to the front of the case, confirmed that the case fan (rear) is channeling hot air out, replaced the fan, etc. 

Would welcome any comments or suggestions on how to regain that initial performance and low fan noise (i.e., cool cpu) or if anyone has found a heat sink with an attached molex powered fan that would fit in this oem, mid-sized case.  I suspect that the good heat sink with fan attached would solve the problem (in fact, I tried secure a small fan to the oem heat sink but it wouldn't stay attached - may have to try again). I know I should probably wait the 200 hours for Arctic Silver to bond before posting but since I've had this problem before I don't think that it is going to make a difference.

Thanks in advance.

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rdunnill
5 Iridium

Re: Dimension 4700 Post CPU Upgrade Fan Noise

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I have the issue of noise with the 2350 ... at high CPU utilization, the fan is running at full speed.

The P4 3.6ghz is a hot-running CPU -- it's too bad the mainboard can't use a standard 775 heatsink.

Does your heatsink look like this? If not, I presume one of those would help, especially if the airstream were going towards it.

Diehard4700
1 Nickel

Re: Dimension 4700 Post CPU Upgrade Fan Noise

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UPDATE

I purchased the heat sink and shroud recommended by RDUNNILL and it worked great!  Thank You, RDUNNILL.  Highly recommend this setup (air flowing from back of case to front) for the Dell Dimension 4700.

Repositioned the HDD cage from vertical front of case to horizontal bottom of case.  This caused the HDD to run at 50-55C - a little too close to manufacturers max of 60C. A small molex fan behind the HDD solved this.  HDD cage should be elevated to allow air flow beneath HDD.  HDD temps now 40-45C.

Good cable management.  Remove floppy disk cover for air flow. Elevate case at least 2" and make sure that the two exhaust ports on the front, bottom of case are clear. 

The above are inexpensive upgrades that will extend the useful life of your Dell Dimension 4700.  Hope this helps anyone still using one of these dinosaurs.

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Diehard4700
1 Nickel

Re: Dimension 4700 Post CPU Upgrade Fan Noise

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The Specs on above machine:

XP Home SP3

2GB 533 RAM

Antec 500 watt PS

A10 BIOS

3.6Ghz Intel Pentium 4 660 HT w/2MB L2 cache

ASUS Radeon 5450

500GH HDD

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rdunnill
5 Iridium

Re: Dimension 4700 Post CPU Upgrade Fan Noise

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Channeling air out? Shouldn't it be channeling air in from the back and directing it downward via the green shroud onto the heatsink?

The spacing of the heatsink mounting holes on the mainboard appears proprietary, so I doubt a standard 775 heatsink can be used.

 

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Kelbear1
4 Germanium

Re: Dimension 4700 Post CPU Upgrade Fan Noise

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Channeling air out? Shouldn't it be channeling air in from the back and directing it downward via the green shroud onto the heatsink?

Systems with the shroud use the case fan in back to draw heat off the CPU and out of the case.  

Did you say you replaced the fan in back?  If you attach a fan with the 4-pin molex and not to the motherboard like the front fan you added, it will run at full speed and be extremely loud unless it is a very low rpm one.  

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rdunnill
5 Iridium

Re: Dimension 4700 Post CPU Upgrade Fan Noise

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If the fan is not connected to the mainboard, at every boot a fan error message prompting the user to press a key will be displayed.

According to this thread, the older designs (like the 3000) push air out while the 4700 pulls it in.

I never paid attention to what direction my 2350's (nor my 4550's) fan flow was -- I assumed it was on to the heatsink, like every other CPU heatsink I've come across. The power supply has a fan to draw hot air out and there are vents in the case for pressurized air to escape. The fan speed varies, as would be expected, according to the CPU load.

 

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8 Platinum

Re: Dimension 4700 Post CPU Upgrade Fan Noise

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Diehard4700

http://support.dell.com/support/topics/global.aspx/support/kcs/document?c=us&cs=19&l=en&s=dhs&docid=...

There are two different fan/heatsink/shroud assemblies for the Dimension 4700.

Bev.

 

 


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rdunnill
5 Iridium

Re: Dimension 4700 Post CPU Upgrade Fan Noise

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The Dimension 4700 system shipped with an aggressive system configuration that required more direct airflow than previously shipped Dimension systems. For this reason, Dell engineering modified the airflow in the Dimension 4700 to support a cooling solution designed with the fan pulling air into the chassis. The air is pulled in through the back of the chassis and is directed straight to the CPU heat sink and CPU voltage regulator before finally passing by the hard drive and out the front of the chassis.

It is correct to say the airflow is backward compared to other Dimension systems. However, without this difference in thermal design, the Dimension 4700 system would not perform nearly as well.

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Diehard4700
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Re: Dimension 4700 Post CPU Upgrade Fan Noise

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Thanks for all of the helpful responses!  

I reversed the fan direction so that air is channeled into the case from the back, through the heat sink, and out the front.  Unfortunately, after about 6 hours of operation this has not resolved the problem.  I also removed the fan I zip tied to the front hdd cage (used to draw air into case and toward the heat sink (when oem case fan was blowing air out back) .  I'll continue to monitor/experiment with it and report back with the solution, if any, in the future.

My recollection is that I checked the fan air flow direction when I first became aware of this issue several years ago.  The PC came from the factory with the fan positioned such that the air was flowing out the BACK of the case.  For several years, noise was not a problem.  About a year ago, the fan noise became an issue.  I first cleaned the machine then replaced the fan (with several supposedly new ones (they were louder than the original) with the appropriate proprietary MB plug) which didn't help.  I was able to reduce the noise by reinstalling oem fan and minimizing system overhead processes (primarily by removing A/V program - all recent versions seem to be too resource intensive for this old PC).  I've read that MS's SilverLight (used by Netflix) could also be a culprit as Flash videos and DVDs don't tax the cpu as much.  SL 5 has an option to offload graphics processing from cpu to gpu but this didn't seem to help either.

As pointed out by Bev and rdunnill, Dell's position seems to differ from the consensus of forum threads I've read stating that the fan should draw the cpu heat out the back of the case.  Bev notes that there were two fan/shroud/heat sink designs for the 4700 and I don't know which one applies to my machine (MB Dell 0M3918).

Thus far, the machine seems to be running consistently louder with the fan pulling air in from the back of the case and out the front.  Since the machine sits next to me and the noise is bothersome I'll probably reverse the fan to its original position.  So back to square one.

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rdunnill
5 Iridium

Re: Dimension 4700 Post CPU Upgrade Fan Noise

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I have the issue of noise with the 2350 ... at high CPU utilization, the fan is running at full speed.

The P4 3.6ghz is a hot-running CPU -- it's too bad the mainboard can't use a standard 775 heatsink.

Does your heatsink look like this? If not, I presume one of those would help, especially if the airstream were going towards it.

Diehard4700
1 Nickel

Re: Dimension 4700 Post CPU Upgrade Fan Noise

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No, my heat sink looks like this.  The one you refer to on eBay might work better but the green shroud would not connect properly. 

However, I think I'm getting closer to the source of the problem.  I have reversed the fan so that it is drawing the hot air from the heat sink and out the back and I have also repositioned the molex fan so that it channels air directly behind the heat sink/green shroud.  I also upgraded to MS SilverLight 5 although the graphics hardware checkbox is grayed out.

Too early to mark this solved but right now it is quiet and plays Netflix HD perfectly.  Earlier this evening, the machine was quiet after windows loaded but the fan cranked up when an application was started and wouldn't throttle down when the app was closed. 

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