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Gw Instek GDS2204E (200MHz 4 channel DSO) review
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markone:

--- Quote from: nctnico on March 24, 2016, 07:03:17 pm ---
I did however made a slight modification to the fan. It started resonating into the casing which made an annoying sound. Instead of going for a new fan ... -snip

--- End quote ---

Those ADDA fan are cr@p, i changed mine with an 60x60x15 Sunon Maglev (MB60151V3-000U-A99), much less noise and much more air flow, actually internal scope's case temp dropped a lot.

The original 20mm deep fan falls to close to analog front-end metal shielding and does not work properly, the resulting air flow is much lower than spec sheet, the 15mm model has instead enough room to work good. 
nctnico:
The Sunon fan you choose is rated at 25dB where the original Adda fan is rated at 18.4dB which translates into the Sunon fan being 4 times louder but I guess the Sunon fan also moves a lot more air. I'm sorry but I don't see how the Sunon fan can be more quiet than the Adda fan when you just compare the fans as they are by themselves. Mounting the original Adda fan with the rubber mounts has lowered the fan noise a lot! All in all I don't think the original Adda fan is a bad choice perse if you look at the specs but it is not a high quality fan and any unbalance can easely couple/resonate into the casing. I did look at fan replacements but the good & low noise fans from Papst etc start from 25 euro (ex. VAT) and there is not a large improvement where it comes to noise: 16dB versus 18.4dB.
markone:

--- Quote from: nctnico on March 25, 2016, 12:47:57 am ---The Sunon fan you choose is rated at 25dB where the original Adda fan is rated at 18.4dB

--- End quote ---

I worked a lot with fans for forced air cooling systems in power electronic and i soon learned that the last thing that you can trust is the noise rating on spec sheet, especially if you compare them among different brands.

In addition if the application implies high static load / flow, when air "sounds" through metal fins and holes, those numbers become utterly useless.

In this scope it's even worst, the fan placement is wrong for a 20mm deep device, as you can check in your scope the intake side falls about 9mm from the nearby metal shielding that literally suffucate it, you can forget the promised CFM and the alleged dBA, flow is much lower than expected and noise is much higher.

The 15mm model has additional 5mm air space in between that let it work a lot better, no sh!t.

Now facts are that if i put my hand in proximity of scope's fan exhaust grid i feel a much stronger air flow than before and i have LOT LESS NOISE  ;)

Back side bnc connectors now are almost at Tamb while before were about 15 °C higher, also case top in proximity of Zynq chip is now colder.

I would say it's a huge improvement, especially because this room temp can easily exceed 30 °C in summer time (34 °C in 2015 !) and there is still room to further decrease fan speed (and noise) with a series resistor.

Sunon MB60151V3-000U-A99 comes for cheap (1/3 papst cost), has right size for the purpose, much less bearing noise and no vibrations at all.
nctnico:
Hmm now I'm tempted to give that Sunon fan a try and compare... where did you buy it?
markone:

--- Quote from: nctnico on March 25, 2016, 09:58:10 am ---Hmm now I'm tempted to give that Sunon fan a try and compare... where did you buy it?

--- End quote ---

From TME http://www.tme.eu/en/details/mb60151v3-a99/dc12v-fans/sunon/mb60151v3-000u-a99/ but now it's no more available, i think you can only order the slower model (i fear too weak) ha60151v4, available for cheap also from Reichelt.

My suggestion is to go for the V3 model than adjust rotation speed with a series resistor and avoid normal sleeve and ball bearing fans, are much more noisier.

Of course shipping cost does not justify an order only for one fan.
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