Author Topic: DP832 - Fan Replacement 2018 (Read 10289 times)

Gandalf_Sr · « **on:** March 16, 2018, 10:53:13 am »

After working with my new DP832 this week, I decided that the fan was sooo noisy that it had to go. I googled and found this blog/website describing how to switch the noisy Sunon Maglev ME80251v1-000C-A99 fan for a Noctua NF-R8 redux 1800; I got the fan and a 2W 27 Ohm resistor and did the change yesterday. A few comments and then some pictures...

It's a pain to change as you have to take the PSU apart - take lots of pictures showing where all the different plugs go before unplugging everything.

The link I posted above says that the old resistor that measures the fan current (R44) is 15 $\$\Omega\$$ but mine was only 7.5 $\$\Omega\$$ which worried me a bit but he also lists the current drawn by his Noctua as 110 mA - the one I got was only 60 mA and still claims 53.3 m³/Hr. My calcs were that 7.5 $\$\Omega\$$ x 0.15 A = 1.125 V (old) and 27 $\$\Omega\$$ x 0.06 A = 1.62 V (new) so I would have been better with a 19 $\$\Omega\$$ resistor but I figured that the OpAmp that was checking the voltage probably didn't care about 1.62 vs 1.125 volts so I stuck in my 27 $\$\Omega\$$ resistor.

My new fan had 4 wires so I cut the plug off the old fan and connected the new fan to that 2 pin connector (black is 0V and yellow is +12V).

I put it back together and powered up, it seems to work perfectly - no failed fan messages when I turn the outputs on - and the fan is almost inaudible now - it does the short burst of full speed on start up and I can tell that it has quite some capability if it needs to move air. I live in Michigan so the DP832 is likely going to never see more than 90 degrees F ambient and only 72 indoors.

Pictures:
Old Fan
New Fan fitted
R44 (in red box)
System Info showing no-load temp (get that detailed view by viewing the ordinary system info and then pressing buttons under screen (numbers from L to R) 1 - 3 - 2)

taydin · « **Reply #1 on:** March 16, 2018, 11:00:54 am »

Thanks for this info, my DP832A is also starting to get on my nerves with its constant fan noise. Might change mine, too, if I can find this nice fan, that is ...

Gandalf_Sr · « **Reply #2 on:** March 16, 2018, 12:01:45 pm »

I bought my fan from Amazon https://www.amazon.com/gp/product/B00KF7MVI2/ref=oh_aui_detailpage_o03_s00?ie=UTF8&psc=1

Just out of curiosity, what is your fan temperature with no load? (follow 1-3-2 steps above) I didn't record mine before I did the modification.

PTR_1275 · « **Reply #3 on:** March 16, 2018, 03:22:54 pm »

Did you do anything to get the bottom half of that screen showing? (With the temperature)

My dp832 shows the first 3 lines, but it’s fw 00.01.14

JDubU · « **Reply #4 on:** March 16, 2018, 06:02:50 pm »

I can answer that:

Press Utility > SysInfo > M1, M3, M2
where "M1" is is the left-most button on the bottom of the display.

taydin · « **Reply #5 on:** March 18, 2018, 07:02:51 pm »

Mine doesn't show temperature, either. Just device model, serial number and digital version, which is 00.01.13

Gandalf_Sr · « **Reply #6 on:** March 18, 2018, 07:57:39 pm »

When you are seeing the 3-line System Info do this...

Press M1, M3, M2 (where "M1" is is the left-most button on the bottom of the display) and the extra information will magically appear.

taydin · « **Reply #7 on:** March 20, 2018, 03:05:03 am »

Ok that worked. Immediately after turning on my 832A, the temperature is 28.9 celsius.

Gandalf_Sr · « **Reply #8 on:** March 20, 2018, 11:13:52 pm »

Cool, so you have the same temperature reading as I do. I have run it at about a 100W and it was quiet and cool

bson · « **Reply #9 on:** March 21, 2018, 03:30:43 am »

Interesting, my DP832 non-A doesn't have the temperature readout...

Edit: never mind, I did a firmware update to 1.14 and I now have it, too.

Wolfgang · « **Reply #10 on:** September 30, 2018, 12:59:00 pm »

I started an opinion poll about the RIGOLs

https://www.eevblog.com/forum/testgear/what-is-your-opinion-of-the-quality-of-the-rigol-dp832(a)/msg1856247/#top

Please give a rating of your own experiences with this stuff - good or bad, whatever it may be.

Thanks
Wolfgang

Pinkus · « **Reply #11 on:** August 13, 2019, 01:31:58 pm »

I have finally found time to replace the fan of my DP832.... the volume of the fan noise was always annoying me.
Though a surprise was waiting:

I wanted to replace it with the above mentioned Noctua, thus I purchased one for about 10 Euros.
But during the conversion I noticed that it was not necessary at all, these 10 Euros can be saved.

1) The Noctua allegedly has the same air performance as the original Sunon fan, but subjectively it produces much less air. It rotates with 1600 rpm where the original Sunon runs with 3200 rpm.

2) The fan cover on the back of the DP832 covers approx. 50% of the surface, i.e. the fan has to produce an unnecessary amount of power to squeeze the air out of the small openings.

Here I thought, to compensate the lower air pressure of the Noctua I would just remove the fan cover of the back of the DP832.
Therefore I separated the fan cover with a Dremel and replaced it with a thin grille cover. The reason was so that the Noctua fan could produce about the same air performance (without the fan cover) as the Sunon (with the fan cover) due to the lower air resistance.

First try: original Sunon fan without the fan cover ..... and ..... whow! The whole unit is 10dB quieter, so it's only half as loud as before! Just by removing and replacing the fan cover. Probably due to the eliminated turbulence at the sharp corners of the cover and of course of the removed extra resistance.

2nd step: Since the air resistance now has become much smaller by removing the cover, the original fan can now turn slower for the same amount of air. A 47 Ohm resistor in series makes the DP832 very very quiet with approximately the same amount of air running through the electronics. In fact, it is that quiet now, that the DP832s chirping display illumination is disturbing.

Well, since I had the 90mm Noctua fan already purchased, I now installed it together with the 3D printed adapter from Thingiverse I already printed. Result: the DP832 is now almost inaudible (but the display).
Note: since this fan needs less power and the DP832 gives an error message, I had to connect 220 Ohm in parallel to the fan.

So, long story short: save your money, you don't need a new fan. It is sufficient to remove (Dremel) the fan cover to lower the volume already by 50%. If you want to make it even quieter, solder a 47 Ohm resistor in series with the fan (you might need to connect the mentioned 220 Ohm resistor in parallel to the fan connector).

Edit:
Temperature:
(see post above how to switch on the temperature display).

Idle (no load): 30.5°C after some time
90W load (* see below): 76°C after 2 hours
after switchoff the load (=idle) and 5 min. waiting time: back to 55°C

*= I set channel 1 and channel 2 to 15V and 3.2A; I then connected them serially (30V, 3.2A max) and used an electronic load to draw 3A. I let it run for >2 hours.

Vaiti · « **Reply #12 on:** August 14, 2019, 07:16:11 am »

Quote from: Pinkus on August 13, 2019, 01:31:58 pm

I wanted to replace it with the above mentioned Noctua, thus I purchased one for about 10 Euros.

Little confused. The fan mentioned here is a 80mm, Noctua NF-R8 redux-1800. If I understood correctly, this fan doesn't require an adapter as it is the same size as the Sunon already in the rear of the DP832.

But you have a 90mm that needs the adapter? Which fan model are you using?

Pinkus · « **Reply #13 on:** August 14, 2019, 07:51:12 am »

Sorry for the confusion. I purchased a Noctua NF-B9 redux-1600 because it was mentioned in another DP832 thread.
This is a 90mm fan where you need an adapter for.

But as I said above, today I would rather just remove the original fan cover and just buy a 1$ replacement for the cover (eg. here: https://www.aliexpress.com/item/32888214967.html) and then use the existing fan.

Other:
Link to thingiverse: https://www.thingiverse.com/thing:2994987

Check also this link regarding noise / airflow of different fan grill (cover) styles: https://www.pugetsystems.com/labs/articles/Effects-of-Grill-Patterns-on-Fan-Performance-Noise-107/. After reading this, you will stay away of any sort of fan grill but the wire-grill.

JDubU · « **Reply #14 on:** March 21, 2020, 03:43:28 pm »

I finally got tired of the unbearable fan noise on my DP832 and did the replacement. It is now really, really quiet. Just the soft sound of moving air.
I cut out the existing fan grill with tin snips and a sheet metal "nibbling" tool and replaced it with a wire grill plus a rubberized sheet metal edging strip to smooth the airflow at the edge of the cutout. A parallel 250 ohm 2W resistor was also added to avoid the Rigol fan fail error message (actually eight parallel 2K ohm 1/4 W resistors because I already had them).

Here are the replacement parts:

Fan: Noctua NF-R8 redux-1800
Replacement grill: https://www.amazon.com/gp/product/B016N6X06K/ref=ppx_yo_dt_b_asin_title_o05_s00?ie=UTF8&psc=1 (needs longer, 3/8" screws that I already had)
Edging strip: https://www.amazon.com/gp/product/B07BPCB8WH/ref=ppx_yo_dt_b_asin_title_o02_s00?ie=UTF8&psc=1 (really nice stuff -- need to cut it with tin snips since it has metal clips inside)
Connector: https://www.amazon.com/gp/product/B07V2XSJZ6/ref=ppx_yo_dt_b_asin_title_o01_s00?ie=UTF8&psc=1 (JST-XH 2 pin -- Caution: the color of the red/black wires are reversed compared to the original fan wiring)

Gandalf_Sr · « **Reply #15 on:** March 21, 2020, 04:23:48 pm »

Looks good, didn't you want to change the big resistor on the PCB?

JDubU · « **Reply #16 on:** March 21, 2020, 04:31:03 pm »

Quote from: Gandalf_Sr on March 21, 2020, 04:23:48 pm

Looks good, didn't you want to change the big resistor on the PCB?

I would have preferred to do that, but I didn't want to take everything apart to get good enough access to it.
Also, I wanted to be able to put the original fan back in easily if the replacement didn't work out (e.g. not enough air flow).

klausES · « **Reply #17 on:** March 21, 2020, 04:40:13 pm »

If you remove the grill from the sheet metal of the back wall
(a good move and nicely protected the cut edge)
you should turn it over right away.

The sheet metal cross was the only reason that was justified to have the fan sucked out of the housing,
since the stall noise (if the suction side is close to a sheet metal cross) would have been much louder.

Since this unfavorable circumstance no longer exists, it would be more favorable in terms of flow technology to blow the heat sink.

Even if e.g. the PTC / NTC sits further forward or even in the front for measurement and thus shows a lower temperature of fresh air drawn in
(housing under negative pressure) (this would only be obviously better)
the actual effective temperature is reduced when the air is blown (upside down fan) inside and on the components.

Since the temperature difference between the outside air and the heat sink is decisive here,
the amount of heat that is dissipated when the outside air that is not preheated is blown in is really higher.

JDubU · « **Reply #18 on:** March 21, 2020, 04:46:16 pm »

Quote from: klausES on March 21, 2020, 04:40:13 pm

If you remove the grill from the sheet metal of the back wall
(a good move and nicely protected the cut edge)
you should turn it over right away.

The sheet metal cross was the only reason that was justified to have the fan sucked out of the housing,
since the stall noise (if the suction side is close to a sheet metal cross) would have been much louder.

Since this unfavorable circumstance no longer exists, it would be more favorable in terms of flow technology to blow the heat sink.

Even if e.g. the PTC / NTC sits further forward or even in the front for measurement and thus shows a lower temperature of fresh air drawn in
(housing under negative pressure) (this would only be obviously better)
the actual effective temperature is reduced when the air is blown (upside down fan) inside and on the components.

Since the temperature difference between the outside air and the heat sink is decisive here,
the amount of heat that is dissipated when the outside air that is not preheated is blown in is really higher.

Good points.
I'll give it a try.

timber23 · « **Reply #19 on:** March 26, 2020, 07:41:18 pm »

Quote from: JDubU on March 21, 2020, 03:43:28 pm

I finally got tired of the unbearable fan noise on my DP832 and did the replacement. It is now really, really quiet. Just the soft sound of moving air.

Thank you for presenting your modification and the part list. After my first test I wondered that the fan did not work at all... As you mentioned red and black are swapped...
For comparison I measured the sound level before and after the modification. I can still hear the fan. It is still loud from my point of view. Maybe I have to put a resistor in series reduce the voltage and rpm a little bit? The idle temperature rises to about 27.5 °C after 10 minutes. As suggested I changed the airflow direction to blow inside the device.
Some pictures the process:

JDubU · « **Reply #20 on:** March 26, 2020, 08:30:34 pm »

I tried turning the fan so that it blew inward and it definitely lowers the internal temperatures compared to the fan blowing outward.
However, it is also a bit louder when blowing inward and adds a high pitch whine, caused by the wire fan guard, which I find to be nerve-wracking. I switched it back to blowing outward and it is currently the quietest fanned instrument on my bench. I figure that I can always turn it back around if the need arises. Meanwhile, I will leave the DP832 over temperature protection (OTP) enabled.

klausES · « **Reply #21 on:** March 26, 2020, 10:41:04 pm »

Quote from: JDubU on March 26, 2020, 08:30:34 pm

...However, it is also a bit louder when blowing inward and adds a high pitch whine, caused by the wire fan guard, which I find to be nerve-wracking...

This is the typical problem when formations are close to the suction side.
This can range from stalling noises to vibrations of the air column (between the obstacle and the wings).

Try to place the fan further in with distances into the housing (preferably rubber ones for decoupling,
10mm may be enough), or you can try to move the grid 10mm further out (with spacers).

eutectique · « **Reply #22 on:** April 02, 2020, 05:42:51 pm »

Got my DP832 recently and stumbled across this thread.

Just for the record, Noctua has two versions of NF-R8 redux-1800 fans: PWM (4-pin) and non-PWM (3-pin). They differ in current consumption, other characteristics are the same.

Sunon Maglev ME80251	145 mA
NF-R8 redux-1800	110 mA
NF-R8 redux-1800 PWM	60 mA

Non-PWM version is quite close electrically to the original fan and probably wouldn't need a different resistor.

JDubU · « **Reply #23 on:** April 02, 2020, 06:14:32 pm »

Quote from: eutectique on April 02, 2020, 05:42:51 pm

Got my DP832 recently and stumbled across this thread.

Just for the record, Noctua has two versions of NF-R8 redux-1800 fans: PWM (4-pin) and non-PWM (3-pin). They differ in current consumption, other characteristics are the same.

Sunon Maglev ME80251 145 mA
NF-R8 redux-1800 110 mA
NF-R8 redux-1800 PWM 60 mA

Non-PWM version is quite close electrically to the original fan and probably wouldn't need a different resistor.

I used the Noctua 3 pin version. Measured current draw in open air was 95mA at 12V. The specs are for max current draw.
Didn't measure the existing Sunon current draw, but here is a video where it was measured in open air to be about 160 mA: https://www.youtube.com/watch?v=b0kTXX8zXSo. (time 3:35)

I did not try the Noctua in the DP832 without the parallel 250 ohm resistor.

timber23 · « **Reply #24 on:** April 02, 2020, 08:05:23 pm »

Quote from: JDubU on April 02, 2020, 06:14:32 pm

I did not try the Noctua in the DP832 without the parallel 250 ohm resistor.

I tried it. It doesn't work. When you switch on a channel than it will be automatically disabled. Furthermore the system test procedure shows that fan fails. That is why I added the parallel resistor. I have the 3-pin version as well.

Gandalf_Sr · « **Reply #25 on:** April 02, 2020, 11:51:23 pm »

Go back and read my first post. There's a picture of the PCB with a large resistor that I drew a red rectangle around in one of the pictures. That resistor carries the current drawn by the fan and the voltage across that resistor is what the DP832 uses to detect whether the fan is running or not. You need about 1.2V across it when the fan is running, achieve that and the DP832 will not have issues with failed fan messages. Its really simple, Ohms law.

Gandalf_Sr · « **Reply #26 on:** May 16, 2020, 12:29:41 am »

I got a second DP832 a week ago and ordered a new fan, same one as before. I took the lid off today and the PCB is a new one and there is no big resistor! I took pictures and will add soon but what did I do?

I measured the current draw of the old fan at 120 mA, the new one is only 60 mA so I added a 200 $\$\Omega\$$ 2W resistor (4 x 820 $\$\Omega\$$ 1/4 W resistors in parallel) and put that across the fan connection. My calculations say that it only draws 0.7W so 2W seems reasnable.

It runs fine. I loaded up the supply and the fan cranked up to cope.

mbedwani · « **Reply #27 on:** July 14, 2021, 03:02:05 am »

Looks like Rigol has changed the Fan to new model (Protechnic) in by new PSU. I used a Noctua NF-A8 FLX 3 pin FAN, Here is what I did.

https://bedwani.com/wordpress/2021/07/07/making-the-rigol-dp832-psu-quiet/

Mark.

pushrax · « **Reply #28 on:** August 22, 2021, 05:05:51 pm »

I have an older DP832, and finally got around to doing this mod. Thank you to everyone who posted useful information here. First I removed the grill with a dremel, and then replaced the fan.

My unit's board had a 7.5 ohm current sense resistor like the original poster. I measured around 1.2V across the resistor during boot up when fan spins up to max (~160mA draw). My replacement fan (some old DeepCool fan I had laying around) measured around 0.7V during that step (~90mA draw).

1.2V/0.7V ≈ 13Ω/7.5Ω. I desoldered the resistor and replaced it with 13.5Ω (two 27Ω 0.25W resistors in parallel). The unit is working perfectly and is super quiet now.

The total power across the current sense resistor peaks ~100mW, so minimal waste.

sequoia · « **Reply #29 on:** January 02, 2022, 05:32:37 am »

I also ended up replacing the stock fan, as it was unbearably loud...

Used also Noctua NF-R8 redux-1800 (non-PWM version).

My unit has V03.02 top and bottom PCBs (dated 2018-06-12) and the fan current sense resistor is now done using three SMD resistors (although looks like through-hole resistor could still be used with this PCB, see attached photo...R210 vs R206-R208)

Didn't feel like taking everything apart to be able to swap out the current sense resistors, so made a short adapter cable from 2-pin JST to 4-pin PC fan connector (female), so no need to modify fan at all....

I ended up also using a parallel resistor in the adapter cable to avoid fan error... 330ohm 2W resistor brought up the current current consumption within 5mA or so to the original stock fan (my unit came with a Protechnic MGA8012HR-O25 fan).

Kugelsicher · « **Reply #30 on:** October 15, 2022, 08:10:48 am »

Got a DP832 and, same as everyone here, noticed that it can be very loud. I found this thread and read about everyone's experiences and fixes, which made me want to do some testing to validate some of the theories. From the start, my concerns were the lack of headroom on the heat sink temperature at max load and the reduction in airflow potentially causing the smaller heat sinks that aren't monitored to overheat.

My DP832, purchased in August of 2022, has "Digital Version" 00.01.16 and came with a Protechnic MGA8012HR-O25 series b fan.

Here are the 80mm 12VDC fans included in my testing along with the specs the listed on their datasheets:
Listed Specs
NMB 3110SB-04W-B50-E00 140mA 41.3CFM 0.150inH2O 30.0dBA
Protechnic MGA8012HR-O25 series b 240mA 37.2CFM 0.123inH2O 34.6dBA (Stock)
Noctua NF-R8 redux 1800 3-Pin 110mA 31.0CFM 0.141inH2O 17.1dBA
Noctua NF-A8 FLX 3-Pin 70mA 29.7CFM 0.196inH2O 16.1dBA

First, I measured the 3 current sense resistors individually and in parallel:
Resistor: 16.2 || 16.2 || 100 = 7.49 Ohm (7.52 Ohm Measured)

Next, I measured the actual current and flow rate. The airflow coming out of a fan is like an inverted vortex which makes extrapolating the CFM from wind speed very difficult as the velocity is much higher at the edges. The air flow is also at an angle outward, away from the fan axis, introducing sine error. To solve this, I designed a simple flow collimator to straighten out the flow and make it relatively even across the exit surface. Then, I just multiplied the measured ft/min by the area of the exit on the collimator to calculate CFM. I used a Modern Device MD0555 Anemometer for the measurements. Note, the collimator restricts flow so the CFM measurements shouldn't be compared against the no-load value provided on their datasheets; but this test shows the relative performance of each fan and is a base-line for later tests. Also know that although I powered the fans from an external supply, was mindful of consistent placement of the collimator and sensor, and allowed the multimeter reading to stabilize before recording the reading, there were still enough uncontrolled variables to cause significant error on all of the following measurements. I'm showing 3 digits of precision but the final digit is definitely within the noise of my measurement setup.

On the Bench Measured Specs @ 12.4V
NMB 3110SB-04W-B50-E00 140mA 34.8CFM
Protechnic MGA8012HR-O25 series b 125mA 30.7CFM
Noctua NF-R8 redux 1800 3-Pin 104mA 23.5CFM
Noctua NF-A8 FLX 3-Pin 54mA 21.9CFM

I then installed each fan inside the case, placed the collimator at the exhaust, and measured the installed CFM for each fan.
Installed, Stock Case Measured CFM @ 12.4V
NMB 3110SB-04W-B50-E00 12.9CFM
Protechnic MGA8012HR-O25 series b 11.3CFM
Noctua NF-R8 redux 1800 3-Pin 10.8CFM
Noctua NF-A8 FLX 3-Pin 7.9CFM

Following this, I cut away the metal that makes up the stock fan guard, replaced it with a standard 80mm wire fan guard and measured the installed CFM again (still with the collimator at the exhaust).
Installed, Cut-Away Case with Wire Guard Measured CFM @ 12.4V
NMB 3110SB-04W-B50-E00 28.4CFM
Protechnic MGA8012HR-O25 series b 25.8CFM
Noctua NF-R8 redux 1800 3-Pin 14.2CFM
Noctua NF-A8 FLX 3-Pin 17.0CFM (I retested this to make sure I hadn't swapped the value with the other Noctua; it is correct)

As you can see, cutting away the stock fan guard and replacing it with an off the shelf wire guard has a huge positive affect on airflow. I did not measure noise during these tests.

Back when the stock fan was installed, I soldered some sense wires to the fan's current resistor and fan header and ran them out of the case to determine how the fan was controlled. I used these wires to measure the current and voltage of the fan and also to apply a load resistor in parallel with the fan to adjust the fan's apparent current draw. The values are below for you to judge for yourself; but my conclusion was that the fan is voltage controlled not current controlled. When the load was increased, the voltage decreased 3% while the current increased 41%. The small additional V-drop with added load is due to ~380mOhm resistance in traces or something between the voltage sensing & the fan connector
IDLE (No load on PSU) comparison:
Without vs With 220 Ohm Resistor in Parallel with Fan
Fan Voltage: 8.25 to 7.99 V
Resistor Voltage: 0.622 to 0.877 V
Current: 83 to 117 mA (calculated)

FULL LOAD (enough load for the DP832 to max out the fan)
Without vs With 220 Ohm Resistor in Parallel with Fan
Fan Voltage: 12.6 to 12.2 V
Resistor Voltage: 0.969 to 1.355 V
Current: 129 to 181 mA (calculated)

Next I reinstalled the Noctua NF-A8 in the case (accidentally blowing inward), plugged it into the DP832, and fully reassembled the power supply. I then ran a few timed load tests using a DC electronic load to compare these values to the same tests I had run earlier with the stock Protechnic fan. Note, a low voltage, high current load results in the most dissipation in the pass transistor because the 30V channel transformer taps are listed as 15V, 25V, 33V (probably significantly higher actual AC voltage for margin). So at 1V output the transistor is burning 15V transformer tap - 1V out = 14V times the current.

The stock results are first.

--STOCK HARDWARE--
Fan: Protechnic MGA8012HR-O25 series b
Fan Voltage Range:   8.22 - 12.60 V (Measured at empty diode pads beside connector)
Resistor:        0.646 - 0.969 V (Measured at Current Resistor test points)
Current:        86 - 129 mA (Calculated from V_resistor)
NOISE TEST
Conditions: Measured in final seconds of TEST 3 with meter sitting on top of the PSU at the very front, facing forward and on the flip-stand
Max Noise: 62 dbA
TEMP TEST 1
Conditions: 30V, 3A Load for 1 Hour
Final Temp: 72.7 C
Ambient Temp: 24 C
TEMP TEST 2
Conditions: 1.4V, 3A Load for 30min
Final Temp: 89.8 C
Ambient Temp: 24 C
TEMP TEST 3
Conditions: Ch-1 & Ch-2 in Parallel, Each Set to 1.4V, 2.45A; for 10min
Final Temp: 74.8 C
Ambient Temp: 25 C

--NEW FAN BLOWING INWARD, BUILT-IN GUARD CUT AWAY, WIRE GUARD ADDED--
Fan: Noctua NF-A8 FLX 3-Pin
Fan Voltage Range:   8.600 - 13.17 V (Measured at empty diode pads beside connector)
Resistor:        0.273 - 0.403 V (Measured at Current Resistor test points)
Current:        36 - 54 mA (Calculated from V_resistor)
NOISE TEST
Conditions: Measured in final seconds of TEST 3 with meter sitting on top of the PSU at the very front, facing forward and on the flip-stand
Max Noise: 54 dbA
TEMP TEST 1
Conditions: 30V, 3A Load for 1 Hour
Final Temp: 53.6 C
Ambient Temp: 25 C
TEMP TEST 2
Conditions: 1.4V, 3A Load for 30min
Final Temp: 61.5 C
Ambient Temp: 25 C
TEMP TEST 3
Conditions: Ch-1 & Ch-2 in Parallel, Each Set to 1.4V, 2.45A; for 10min
Final Temp: 55.2 C
Ambient Temp: 25 C

Here I noticed that the fan was blowing the wrong way and reversed it.

--NEW FAN BLOWING OUTWARD, BUILT-IN GUARD CUT AWAY, WIRE GUARD ADDED--
Fan: Noctua NF-A8 FLX 3-Pin
NOISE TEST
Conditions: Measured in final seconds of TEST 2 with meter sitting on top of the PSU at the very front, facing forward and on the flip-stand
Max Noise: 57 dbA
TEMP TEST 1
Conditions: 30V, 3A Load for 1 Hour
Final Temp: 76.2 C
Ambient Temp: 26 C
TEMP TEST 2
Conditions: 1.4V, 3A Load for 30min
Final Temp: 89.6 C
Ambient Temp: 25 C

At this point I was very disappointed, having reduced the noise a bit but not having improved the temperatures at all. The contrast of the inward blowing versus outward blowing fan tests made it clear to me that the airflow path was a key problem. So, I designed (and redesigned several times) a flow guide for the inside of the case and printed it in a flame retardant rated PC-ABS filament (the prototypes were all in PLA but I didn't feel safe leaving that inside something that can fail over 100C). The final tests were with the final version of the flow-guide installed.

--NEW FAN BLOWING OUTWARD, WITH INTERNAL AIR GUIDE, BUILT-IN GUARD CUT AWAY, WIRE GUARD ADDED--
Fan: Noctua NF-A8 FLX 3-Pin
NOISE TEST
Conditions: Measured in final seconds of TEST 2 with meter sitting on top of the PSU at the very front, facing forward and on the flip-stand
Max Noise: 56 dbA
TEMP TEST 1
Conditions: 30V, 3A Load for 1 Hour
Final Temp: 62.7 C
Ambient Temp: 26 C
TEMP TEST 2
Conditions: 1.4V, 3A Load for 30min
Final Temp: 75.2 C
Ambient Temp: 25 C

Finally, I tested the smaller heat sinks and found the temperatures to be with 10 C of room temp in most cases. With a large load on the 5V rail, the tall heatsink on the right side (viewed from the front) of the upper board reached 53 C after 15min. This was the highest value measured on the smaller heat sinks. I was sick of testing at this point and didn't write most of the values down; so I don't have a fully dataset for this.

I think this testing makes clear that most of the noise is coming from the airflow past the internals of the power supply and not the fan itself. This makes it more difficult to reduce than expected. I would also advise against simply installing a quieter & slower fan as the heat sinks get very hot with a large load even with the stock fan jet-engining air out of the case. I think a combination of a Noctua fan, cutting away the built-in fan guard area, and adding a wire guard offers a decent improvement without increasing loaded temperatures. Another option is to install a quieter fan blowing inward instead of out of the case. This results in excellent cooling of the primary heat sinks but will increase the temperature inside the case, which isn't good for the electrolytic caps, smaller heat sinks, or transformer (whose internal temperature may already be quite high). It would probably also cause the voltage reference to drift and affect accuracy.

If anyone has any other ideas, please let me know. I'd be up for more testing in a few weeks and the fan still isn't quiet at high loads.

tv84 · « **Reply #31 on:** October 15, 2022, 08:47:05 am »

Nice testing!!

Hexley · « **Reply #32 on:** October 15, 2022, 04:59:03 pm »

Quote from: Kugelsicher on October 15, 2022, 08:10:48 am

If anyone has any other ideas, please let me know.

I wonder if the exhaust air is not being drawn **through** the heat sinks, but rather around them. From the photos, it looks like the natural path would be through the channel between the outer edges of the heat sinks and the adjacent sides of the chassis. That looks like the path of least resistance. But it would not be the path of most effective cooling for the main heat sinks.

An interesting test would be to add a couple of small fans inside the case, blowing directly into the intake area of the heat sinks. These would encourage the air to flow through the inner parts of the heat sink. That hot air would then get expelled by the normal exhaust fan.

The intake fans could be quite small I think -- and therefore very quiet. They could poach power from the main fan since there is power to spare with the retrofitted fan. Perhaps the fans could be mounted with some small printed brackets.

Just thinking out loud, so to speak.

Kugelsicher · « **Reply #33 on:** October 15, 2022, 11:49:30 pm »

Quote from: Hexley on October 15, 2022, 04:59:03 pm

An interesting test would be to add a couple of small fans inside the case, blowing directly into the intake area of the heat sinks. These would encourage the air to flow through the inner parts of the heat sink. That hot air would then get expelled by the normal exhaust fan.

I like this idea and I think I have 4 refurb 40mm 12VDC Sunon fans that I can use to test this out. If so, I'll try it out in a couple of weeks.

Veketti · « **Reply #34 on:** March 04, 2023, 11:50:19 am »

Old topic, but still valid. I got fed up to the fan noise and cut out the fan cover. That made the noise so much lower that no need to replace the fan. Did the same thing to my DS2000 scope but there no noticeable differences. I quess I need to change the fan on that scope then..

Veketti · « **Reply #35 on:** March 19, 2023, 06:19:13 pm »

Tried two different fans which were not yet tested here. Both Sanyo fans:
San Ace 9RA0812S4001. 38.6CFM / 64.8m3/h 0.210 in H2O / 52.3Pa 31dbA 80x25mm
San Ace 9RA0912H40011 52CFM / 87.6m3/h, 0.19 in H2O / 47.3Pa 31dbA 92x25mm

That 80mm fan would have been perfect, but it draw 40mA less current than the original and gives fan error. It was around 2dbA more quiet than the stock fan without the grill. Still having better performance. 28.7°C temperature with one channel on 10mA load.

As I had the thingverse 80->92mm adapter printed I installed the San Ace 92mm fan. Same noise than the original fan without the grill 40dbA, but that thing moves some serious amounts of air. So what I learned from this is that these San Ace fans are the highest quality fans that I've seen. Each of them seem to be balanced, which I haven't noticed on other brands. Also blade design is good that it is quiet for the amount of air it moves.


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Author Topic: DP832 - Fan Replacement 2018 (Read 10289 times)

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