Volcano 7 revisited

[frombadtraverse]

Well I didn’t like the option of turning off the FOC. I think that is an important safeguard. My Volcano 7 (not 7+) is a heatsink that I like. It has an 80mm fan and seems to do a good job of cooling. The problem was that it didn’t start with a high enough speed for my motherboard; and the motherboard would shut off.

It is thermistor controlled and would get up to speed when the ambient temperature rose in the enclosure. I determined that it would be an easy mod to make the fan start at a higher speed. The highest speed is determined by the maximum rate of the fan itself.

I took it to the bench to see just what was going on. When it was going at the lowest speed the tach pin was putting out 60hz. When the thermistor was heated by my soldering iron, at max speed, the tach pin was putting out 160hz. This seems to be what the motherboard is sensing. I decided to add a resistor in series with the thermistor to make the fan run half way between the low and high speed (approximately) when the thermistor was at room temperature (about 21 C).

What I did was cut off the heatshrink, solder a parallel resistor to the thermistor, and add new heatshrink. The value I decided on was an 18K ohm resistor, though I think a 20K would do nicely also. The value of the thermistor at 21 C is approximately 10K (the value written on it). At high temperatures the thermistor went down to 500 ohms. With the 18K resistor in parallel with the 10K resistor the value of resistance was 6.4K. The 18K at max temp with the 500 ohm thermistor is 486 ohms. This is well within the tolerance of the fan.

All that is left is to show you a couple of pictures. As you can see the tach reads 107.2 Hz with the 18K in parallel with the thermistor.

Oh, and the FOC works fine on my Soyo Dragon Ultra now. And my CPU temps are 2 degrees cooler (43 vs. 45 C) running UD at 100% processor usage, with the same case temperature.

[frombadtraverse]

And a closeup of the resistor, thermistor parallel combination:

[ImaginAsian]

Nice Work FBT! I enjoy reading custom mods especially those which illustrate simple and practical results.

I take it you don't run into the Bootup problem anymore? Also, is the thermistor the "greenie"? It looks very much like a Cap.

Would you mind writing a small article on something like "Modifying Thermo-Controlled Fan to Increase Initial Airflow"? It would make a great BBT article that could help kick off the articles section!

[prod]

hehe exactly what I was thinking of doing. To bad I couldnt get my arse out of bed to do it.:thumbsup:
A few questions on your setup:
What is your cpu speed and voltage at 43C? My AthlonC 1.33 overclocked to 1.53 at 1.89v is 47C max, 30C case.
Do you keep the thermistor suspended from the fan or do you have it jammed between a couple fins on the heatsink like me?
And what do you get now for max fan rpms?

And some karma for redoing the heatshrink. ;)

[Alakazam]

Excellent FBT, that would certainly be a good article to have for the members. Great pics too, nice and clear.

[Darksword]

Nice mod job. :)

I've also heard of people simply taking the temp probe and pointing it down into the heat sink itself, where it heats up quite easily. No modding needed.

[frombadtraverse]

Prod the fan speed at case temp of 30C is 4500rpm according to the Soyo HW monitor. I just have the thermistor reading the case temp. The fins are a good idea but that still wouldn't help me on a cold boot, wouldn't heat up fast enough, so I just made the cold start speed faster. I'm running an XP1900+ at 1.725v and 146 FSB (still locked at 12X) at 1.75G. Now the case temp is 30C and the CPU is at 40C. The other night it was 33C and 43C, holding fairly steady at 10C above case. You could also just put a 1/2 Watt pot 10K ohm with a 500 ohm resistor in series and have a variable speed fan. I rather like the temperature changing fan, just thought the start up speed was too low.

IA, I'm looking into playing with some other brands of temp sensitive fans (case fans). I'll work on it. Yes, the green thing that looks like a tantalum cap is the thermistor. It doesn't work the 'brute force' way of changing the driving voltage to the fan (it's too small a wattage), I'm looking into the exact mechanism, but suspecting it regulates voltage to a secondary coil to increase speed. That would be more efficient.

[Skamp]

I might get one of these babys for my PIII machine tomorrow,its been reviewed well and even said it does as good a job as the swiftech!!

[prod]

skamp: if you are after performance (duh) thermaltake sells the fan separately. Mount it on an AX7 and you should be good to go. That was my first choice but the AX7 wouldnt fit in my oem case.
The actual volcano 7 heat sink is smaller and not quite as good for cooling. Nice blue anodize tho :toocool:

I didnt stick the thermistor in the fins to help with the startup problem. I think it helps the fans speed to scale better as the cpu warms up. But I may also use the soldered resistor to increase speed overall.
Some people have just clipped the thermistor off and joined the wires to make a real screamer, but I rather like the thermal control feature. Just needs a little tweaking is all :)

[Skamp]

Im Only going for this HSF mainly because the shop 15mins away actually has it,which is amazing for my city(feck all available here,have to order from Sydney usually)and it does quite a good job.