Notes on Zalman VF700 GPU Cooler series

[fstroupe]

I recently purchased my third cooler in the Zalman VF700 series, a second VF700-Cu, to put on the XFX 7600GT I ordered at the same time. I previously had reviewed a VF700-Cu, and a FS-VF here at OCIA.net.

I know the instructions for installation of this cooler by heart, from documenting them myself on two reviews, and reinstalling a few times. I have never had the first problem, and really love these coolers.

When I got my parts, I went ahead and installed the Zalman on the card before installing the card in the rig. No POST, no beep, which on an Abit mobo means video card prob. Tried the 7600GT in another rig, NoGo, put my old card back in, POSTd fine.

So, I reinstalled the old cooler (with a lot of thermal paste like it came with) put it back in the box and did an RMA. I never thought about trying it with the old cooler before packing it back up...dummy me. Heat probs was far from my mind.

There was an odd marred spot on the Zalman HS base, away from where the GPU sits, but I kind of assumed that I had bumped the "seal" that keeps the GPU from being crushed during installation. Its pretty easy to mar a mirror finish as was on the Zalman.

Got the card back from "repair RMA" (which told me that it probably worked when they tested it) a few weeks ago, and installed it with the stock cooler on it. Last night, I decided to reinstall the Zalman. Idle temp went from 48C to 52C, so I knew something was wrong. I was too tired to investigate, so left it for the time being.

Started futzing with it this morning. I had put a little more AS5 than I normally would, so I reapplied it in the paper thin coat that AS recommends, and reinstalled the VF700.

Fortunitely, the 6 and 7 series geForce GPUs will withstand the rediculously high "Core Slowdown Threshold" shown on the temp monitoring screen...the 91C temp (**gasp!**) would have fried some GPUs. Needless to say, my finger nearly went through my case power button turning the damn thing off.

So, I reapplied too much AS5, and went back to 52C idle. This time, after putting the mounting screws barely in, I moved the HS back and forth some to seat the GPU in the AS5, like I do when I apply AS5 to a CPU.

Started Googling the problem. Ended up going to NewEgg's reviews and started reading through the more than 400 reviews for this item.

I really found none that had my exact problem...though many said that they now had temps in the 50C's...which is too damn hot for this excellent cooler...and had had temps in the 60C's with the stock cooler...which is also much hotter than my experience with stock coolers. Also, one guy mentioned that he had looked closely before putting the card back in his rig, and he (after not following the installation instructions obviously) could see daylight between the GPU and HS base. (luckily he looked!!)

Last, I went back and looked at my original review, just to see if I had forgotten anything, which I hadn't.

So, I pull the card again, and take off the cooler. The aforementioned "marred" spot was now a scratch. Hmmm...

I get under some good light, put on my glasses LOL, and observed the thing for the umpteenth time. Hard to tell, but it appeared that the "seal" was touching the HS base on one side and not the other.

I used a piece of paper as a gage...sure enough, the HS was touching the seal on one side...meaning that the HS base was probably contacting the GPU unevenly.

I ended up having to screw one side of the cooler all the way down first, and leave the other screw fairly loose. Getting a respectable 39C idle now.

All I can figure is that the seal on the card is somewhat uneven, and the tolerance closer than on the other cards I have used the coolers on. I think that I will try to come up with some kind of shim so I can tighten the other screw. Maybe a small piece of index card...though I really hate to be so ghetto. :oops:

This has to be the fault of the card...I really don't see how it could be a problem with the cooler.

[Overclocked Dirtbike]

Fortunitely, the 6 and 7 series geForce GPUs will withstand the rediculously high "Core Slowdown Threshold" shown on the temp monitoring screen...the 91C temp (**gasp!**) would have fried some GPUs.

My 7600 says it can handle 115 C before shutdown. Anyway, my Blue Orb II was sitting on my desk, HSP down directly touching my desk. I have also slided it around and it is now working wonders for my CPU. I don't understand why it made such a horrific difference on your GPU.

And 52 C is not bad for a GPU.

[fstroupe]

I don't understand why it made such a horrific difference on your GPU.
Because a relatively small section of the heatsink was making direct contact with the die surface due to the "seal" holding one side of the HS away from the die. Probably much less than half.

Not as big of a concern when the manufacture places a large amount of goop there...a BIG concern with the paper thin layer of AS5 as per the manufacturer instructions.

Though, the more I think about it, the seal being unlevel can't be the culprit. My brains are rather fried from a long week at work. Maybe the die is unlevel. I just don't think that one side of the mounting spring on the cooler is that much stronger than the other side. Something isn't flat somewhere.

And 52 C is not bad for a GPU.
Anyone that buys an aftermarket GPU cooler and can't get better than 52C idle temp has been ripped off, especially one that costs ~30 bucks or more. This one is capable of low-mid 30s at 70F room temperature, after the AS5 cures. The stock one was getting 48C (with AS5).

My "Core Slowdown Threshold" is 130C. I think it is 151 on my 6800XT.

[FunkZ]

Is the card pcb warped so that the mounting holes are uneven?

When I put the VF900cu on mine and tightened it down it kinda bends the card slightly because it applies so much pressure.

[fstroupe]

Hmmm....I guess that's possible. Didn't think of that, I kind of assumed that the back brace prevented it. Makes sense.

You know, seems that most of the guys with idle temps in the 50s on the NewEgg reviews (of the ones I read...the last 150 or so) mostly had XFX 7XXX cards. Maybe the board is made of thinner material than earlier cards.

Have to investigate further.

[fstroupe]

Played around some more, the temp holds fast at 39C idle. Guess that's about it, should drop to around 36C when the AS5 cures. Thats about what I expected from it anyway.

[Overclocked Dirtbike]

Sorry, my ignorance...