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EXTRA VRM HEATSINKS
This led to the next idea from the SPCR forum, suggested by diver and golemB: Why not add
some copper to the VRM to catch the existing airflow?
I
bought some Swiftech
MC14 BGA RAMsinks and stuck them on the various hot spots of
the VRM. These are forged copper heatsinks designed for video card DRAM
chips, and seemed ideal for this application. Swiftech claims a
6°C advantage over the competitor. Since the PLL chip also
ran very hot, I added a heat sink to it as well.
To install these heatsinks, I had to temporarily remove the
Ninja. Here are before and after pictures. Note the discoloration of
the board and torroids near the VRM (top center) after running the
system for seven months with poor VRM cooling.
VRM and
PLL before adding heat sinks.
VRM and
PLL with heat sinks installed (and Arctic Silver 5 ready for Ninja
remounting).
Here is a photo looking down through the top case fan. The
copper at the top left is one of the VRM heat sinks. The whitish part
at the top is the base of the Ninja. The foam on the top of the Ninja
duct is also visible. The airflow to this fan is constrained to the
two-inch channel at the top of this photo. As described in Part One,
the foam and
coins in the center are to damp the ringing of the fan hub.
The combination of baffle and heat sinks dropped the VRM temperatures a lot. The main MOSFET heat sink went from “YOW!” hot to too hot to hold a finger on (subjective I know, but I think that would indicate at least a 10°C drop), and the heat sinks on the other MOSFETs and the PLL were now somewhere between warm and hot to the touch. I guess I should have measured the temperatures, but didn’t think to do so.
ADDING A VIDEO
CARD DUCT
SPCR forum responses from diver
and scara
asked: Why not move the video card
heat directly out of the box?
I thought about this for a
while, and came up with a duct that would capture some of the
motherboard fan air flow and direct it across the heat pipe radiators
and out of the box. The duct is composed of the video
card PCB as its bottom, the motherboard as its far side, and styrene
panels
as its top and near sides. The top of this duct would collide with the
north
bridge duct, so it requires a curved cut to let the two ducts mate
properly. Here is a photo of the video card duct before installation.
The notch at the bottom is for a capacitor on the motherboard, the
notch at the top is for the heat pipes, and the
deflector at the top is intended to smooth the air flow.
Video
card duct before installation, back/bottom view.
When installed, this duct sits on top of the video card PCB, and butts
against the motherboard and the back of the case, as shown in this
photo. The motherboard fan is just to the right of this photo. The rear
panel
PCI blank above the video card slot was removed to let the hot air out.
Video card duct after installation.
This duct removed 30~50W of heat from the motherboard air flow, allowing both lower temperatures and slower fan speeds.
OPENING UP THE UNUSED 5.25" BAYS FOR BETTER AIR FLOW
An SPCR forum response from PhillyB
mentioned the Scythe
Kama Bay. This sparked the thought: Why not have
two ingress air streams, one feeding the CPU fan, and the other feeding
the motherboard fan?
If these worked reasonably well, it would be
possible to close up the case, and have dust filters on all air
streams.
The P180 already has a dust filter on the ingress path to the lower
half of the upper
bay, and installing a Kama Bay would provide one for the upper half.
A simple baffle could keep the two streams separated. This would double
the input air flow cross-section and nearly
double the total upper chamber air flow. The Kama Bay (with its dust
filter but without its fan) would occupy the three unused 5.25" bays at
the top front of the case.
Here is a photo with all the fans, ducts and baffles
installed. The
Ninja, north bridge and video card ducts dovetail in the center, the
VRM baffle is above the Ninja duct, and the chamber baffle is wedged
between the motherboard fan and the DVD drive PATA cable. This photo
also shows the last two RAMsinks, mounted on the south bridge and the
TV card processor.
Two
fans, three
ducts, two baffles, and some copper.
The top-half air flow in this arrangement is straight through
the Kama Bay dust filter, the CPU fan and Ninja duct, then out the back
of the case.
The bottom-half air flow is more convoluted. It enters
through the P180 dust filter, goes through the motherboard fan, and is
split into three parts. The center part flows through the video card
duct and out the back of the case. The top part flows through the north
bridge duct, across the motherboard and VRM, into the top case fan
chamber, then through the top case fan and out of the case.
Finally, the bottom part swirls
around the south bridge and TV card, then flows over the near side of
the video card duct, then to the motherboard, where it joins the top
part flowing over the motherboard and out the top of the case.
Installing the Kama Bay required fitting the steel P180 drive
clips to its shell, which meant drilling some holes. These clips are
made from a very hard steel. Unless waste material is clamped to both
sides, drilling the holes causes even Bosch
titanium bits to wander severely. The plastic holders the
clips come on work well as bit guides. Remember: measure twice, drill
once! Here is a photo of the Kama Bay with all the hardware installed,
ready to be put into the case.
Scythe Kama Bay with P180 clips
attached.
The clips need to be bent
outward slightly to engage the chassis slots because the Kama Bay is a
bit
narrower than a standard CD/DVD drive.
Doubling the air flow in this
manner let me close the case and still use slow fans. The motherboard
temperature rose significantly (about 8°C) but not enough to
cause errors.
NOTCHING THE SLIDING CHAMBER
SEPARATOR
SPCR member BigA
suggested: Cut a notch in the rectangular sliding plastic that
separates the upper and lower chambers of the P180.
This allows the
SATA HDD data and power cables to go from the upper to the lower
chamber while still sealing off the air flow. Here's a photo:
Notch in the upper/lower chamber
sliding panel to accommodate cables.
This was probably the
simplest mod so far, and worked well.
SWITCHING TO NEXUS FANS
At this point, I was running with four DustProof AcoustiFans,
all at
5V, their lowest reliable operating point. The system was very quiet —
the house and neighborhood had to be silent to have any chance of
hearing the computer noise. It was too quiet to record with the gear I
had. Interestingly, I could not detect any difference in sound level
with the case open or closed.
However, although the volume
of the noise was pleasingly low, the nature
of it was rather annoying. The CPU fan in particular put out a
thrumming sound reminiscent of a distant propeller airplane. The
motherboard fan also did this, but to a lesser extent. The cause of
this
thrumming was obviously the close proximity of the
downwind side of the fan blades to the Ninja fins and the motherboard
and
video card duct edges. Also, there was a distinct 245-Hz tone.
I could live with the thrumming per se, but
unfortunately
these two
fans were so close in speed that the thrumming beat about once a
second, making it very hard to ignore.
Thinking that a different brand of fan would run at a
different speed and get rid of the beating, I ordered a couple of Nexus 120mm
orange fans. These have long been MikeC's favorites,
and MadShrimp's
comparison notes that the Nexus at 7V significantly
outperforms the AcoustiFan DustProof at 5V at about the same sound
level. I guess the reason I had taken so long to try these fans is that
I just don't like the color. Why can't they make some plain black ones
like everyone else?
When these fans arrived, I did some direct A/B comparison
tests. In free
air, the brand-new Nexus was slightly quieter than the seven-month old
DustProof at each voltage. Of course the Nexus spins slower at each
voltage, so that was no surprise. What was a surprise was the
difference in sound when I put a finger near the fan blades. Both were
annoyingly loud with an obstruction on the upwind side (this effect is
well documented on SPCR and elsewhere). However, on the downwind side,
the difference was striking: the Nexus was much quieter. This
difference appears to be due to the shape of the frame bevel, which is
deeper on the Nexus.
When I mounted a Nexus on the Ninja, there was no audible
thrumming anymore, and the 245-Hz tone was also gone. Encouraged by
this success, I ordered two more Nexus fans, so I could replace all the
DustProofs.
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