Modding the Zalman 9500 Heatsink

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Nov 22, 2005 by Mike Chin

Zalman's CNPS9500 made a very strong showing on our test bench. In the conclusion of our review posted in September, we wrote:

"The Zalman 9500 provides excellent cooling performance, close to the best that we've tested, the Scythe Ninja, and matches the Thermalright XP-120. It provides this performance even when airflow is reduced by undervolting the fan with the included Fanmate, a feature for which we've long applauded Zalman.

"However, similar performance could be achieved at a lower noise level with the two heatsinks mentioned above by using a quiet Nexus 120mm fan. By contrast, the fan in the 9500 is a step backwards even from its predecessor, the Zalman 7000, which sounded nicer (if only slightly quieter) at the same voltage.

"The performance of the heatsink, especially under low-airflow conditions, makes it a prime candidate for a fan swap. This is a more difficult procedure than a standard fan swap, but the results are likely to be well worth the effort. It's been done with both the Zalman 7000 and the 7700 series."

This article is a followup to the last paragraph above. It documents the procedures used to remove the stock Zalman fan and replace it with the guts of a Nexus 92mm "Real Silent Fan", which is the quietest 92mm fan we've yet encountered. The objective was to have a heatsink as quiet as the Nexus-fan modded 7000 and 7700 heatsinks described above ¬ó but with even better cooling performance and all the benefits of the 9500's superior overall design.

THE BEGINNING

We begin, of course, with the stock 9500 that was used for our testing. In case you've forgotten what it looks like, here's a photo:


Stock Zalman CNPS9500.

As you can see in the above photo, two machine screws affix the metal fan bracket to the base of the heatsink. These screws were removed, using a small Phillips head screwdriver with a long shaft. Care had to be taken not to apply pressure against the fan blades, to avoid damage.


Fan and bracket removed.

The photo below shows two smaller screws that attach the fan to the bracket. These were removed to separate the fan from the metal bracket.


The fan attaches to the bracket with two small screws.

The distance between the mounting holes on the fan was measured carefully. It was exactly 4 cm, center to center. Shown below is a Nexus 92mm fan, already cut away from its frame. The Nexus fan came from our long time supporter, End PC Noise. A pair of sharp metal cutting pliers was used carefully to avoid applying torque on the bearing.


Nexus fan cut from frame.

The next photo shows the tiny holes drilled into two of the arms that extend from the center of the fan. They had to be very precisely done. I was off ever so lightly; the distance between the holes to be just under 4 cm, perhaps 3.95 cm. I knew this might be enough to cause a break around one of the holes as the screw was tightened and tension applied. The plastic "arms" are very narrow. I should probably have drilled the hole before cutting the fan from its frame and used a sharp pin of some kind to score the starting point. It was a non-slip, self centering drill bit I used.


Holes drilled for mounting the fan to the 9500 fan bracket.

The remaining arms were cut and trimmed away carefully, again using the cutting pliers and a large file. A layer of 1/16" thick double-sided foam tape was applied between the bracket and the back of the Nexus fan to stop the screws from going all the way into the holes that I suspected might break. The double side tape also added a bit of soft cushioning.

I managed to attach the Nexus fan to the metal frame with only a small crack along one of the holes. With the tape and the other screw, it was secure, and there seemed little risk of the hole breaking open. The photos below show the final result, mounted on the nearest motherboard.


No LED lights in this fan, but it's much quieter.

The work took perhaps an hour. You might be able to do it in less time. There are probably many other ways you could accomplish the same task; using epoxy glue, for example, instead of trying to duplicate the mounting holes. You could also try something more extreme, like using a 120mm fan instead. This would mean the blades have to be outside the recess in the heatsink fins.



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