Sapphire 4850 Fan Mod Gone Wrong

M

Maxtr0sity

Limp Gawd
Joined
Dec 24, 2005
Messages
286
I bought the 4850 during the holidays, turns out, the fan was really loud. It was either on at 100% or completely off. Any ATI related tools didn't fix the problem either and as far as CCC is concerned, it thinks it's a 4800 series card.

So I tried to do my own fan mod with a 5 way switch and some diodes. I measured the fan pin voltage while it was running, about 10V. I figured I can do a range from 5V to 10V on the fan controller. Right as I'm about to complete the mod, I go test the voltage one last time. Except this time, the leads on my voltmeter accidentally touched while measuring the fan. No BSOD, no hickups. The fan turned off, then back on. Except this time, it stays at 8V.

Tolerable noise level, but it no longer changes speeds at all. The 12V from my power supply still supplies the same power, no damage there. But now, the fan stays at a constant speed no matter what load I put on it.

Is 8V some failsafe voltage? Anyone heard of this happening?
 
why not download the new Catalyst drivers which gives you total control over fan speed?
 
Just so you know, 4850 is part of the 4800 series. Notice the 48- before the -50?
 
Smoove910 said:
why not download the new Catalyst drivers which gives you total control over fan speed?
Click to expand...

Many non-reference cards with aftermarket coolers pre-installed only come with a 2-pin fan connector meaning it's impossible to adjust the fan speed without using an actual resistor or potentiometer. If you absolutely must use a non-reference card, it's very important to verify that the card supports fan speed control (most cards with a 4-pin connector do).

I had the same issue with my Gigabyte 8800GT with a Zalman cooler pre-installed..always at 100% - RivaTuner etc. had no effect. Had to buy a Fanmate2 and manually change between "high" and "low" depending on whether it was running games or just sitting at the desktop.
 
You're right, the fan is only a two pin. But shouldn't the graphics card be able to adjust the voltage going to the pins?
 
No, that would almost certainly ensure premature fan failure. Fluctuating voltages are killers.
 
This card?
http://www.newegg.com/Product/Product.aspx?Item=N82E16814102770

Check the fan pins.
Wow, that's really lame. I think that card deserves a 1-star review for the forced fan speeds. Are people on NewEgg really that naive?

Should probably check the reviews and see if anyone mentioned it.
This is why I never trust these custom coolers ATI's partners insist on using. You can barely even find the reference cards anymore.
 
The link points to the 4850, but the 4830 has the same exact cooler and design so I wouldn't doubt it if it had the same problem. I think most people don't notice the noise because they have so many loud fans running as is, it's natural to them, but for me, having a near silent setup, loud noises annoy the bejesus out of me.
 
If you read the reviews on newegg, there are a lot of people who mention the fan speed is always at 100%.
 
Maxtr0sity said:
You're right, the fan is only a two pin. But shouldn't the graphics card be able to adjust the voltage going to the pins?
Click to expand...

Modern fan controllers don't adjust the fan speed by adjusting the voltage. They use PWM which requires an additional wire (usually blue). The fourth (yellow) wire is used to monitor the RPM of the fan.
 
JimmiG said:
Modern fan controllers don't adjust the fan speed by adjusting the voltage. They use PWM which requires an additional wire (usually blue). The fourth (yellow) wire is used to monitor the RPM of the fan.
Click to expand...

or you can use a PWM fan controller, which will hook up to the 3 pin or 2 pin fan and then control the duty cycle: Supplying a consitent voltage, but in pulse timing, which in effect reduces speed.
Many fans have minimum voltage start up requirements, I have wired some case fans to run on 5V instead of 12V and they stop, other times I have wired them to run at 7V. Sounds like time for a good aftermarket heatsink and cooler perhaps, better heatsink would require less fan in the first place. I have had good luck with the Arctic Cooling NV5 for the 7800GTS and also had one on my 6800GT. Nice outside the case design and solid copper heatsink, memory pad contact, and 70mm quiet fan. Maybe they make one for your card, try SVC.com
Good luck,
 
JimmiG said:
Modern fan controllers don't adjust the fan speed by adjusting the voltage. They use PWM which requires an additional wire (usually blue). The fourth (yellow) wire is used to monitor the RPM of the fan.
Click to expand...

Just FYI, the spec for the 4-wire PWM fan says black and yellow for ground and 12V, green for RPM sensing, and blue for PWM control. However, many also use the old 3-pin black/red/yellow scheme plus a blue wire for PWM. My stock AMD CPU fan actually has black/red/blue/yellow instead (blue is RPM, yellow is PWM). I just wanted to point that out, as yellow could be either RPM or 12V, depending on if they used the old or new scheme. And as my AMD fan shows, it could even be something else, like PWM.

Just to make it idiot proof, the one pin "added on" outside the 3-wire locking tab will be PWM. The opposite end is ground. Of the two in the middle, 12V is next to ground, and RPM is next to PWM.

semiconductorslave said:
Sounds like time for a good aftermarket heatsink and cooler perhaps, better heatsink would require less fan in the first place. I have had good luck with the Arctic Cooling NV5 for the 7800GTS and also had one on my 6800GT. Nice outside the case design and solid copper heatsink, memory pad contact, and 70mm quiet fan. Maybe they make one for your card, try SVC.com
Click to expand...

If you have good airflow and extra room inside your case, I highly recommend the Accelero S1 Rev 2. Passive, with just the side panel 120mm case fan blowing on it, it keeps my XFX 9800GT cooler at full load than the stocker did at idle. http://www.newegg.com/Product/Product.aspx?Item=N82E16835186016
 
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