70 vs 55 m^3/hr fans for Rigol MSO5000?

[JetForMe]

My Rigol MSO5000 is just so loud when it’s running, and I decided I’d swap out its fan with a Noctua. The Rigol OEM fan is a Sunson ME80251V1, a 41 CFM (69 m^3/hr), 3200 RPM fan, putting out 33 db. The 80 mm Noctua options are 55.5 m^3/hr @ 17.7 dB and 53.3 m^3/hr at 17.1 dB. Do you think these lower air flows would have a significant impact on the cooling performance?

From the charts on page 18 of this paper, it seems there are diminishing returns as air velocity increases. I calculate the air flow to be between 2 and 3 m/s (based on which attenuating cable is used), and that seems to have little effect on the thermal resistance:

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[EEVblog]

I'd say good enough for Australia.
If you are worrried, do an A-B test. Stick a thermocouple on the heatsink(s) and log the results.
This would make an interesting video actually...

[JetForMe]

Yeah, I considered doing the A/B test. I wondered what task I could put the Rigol to that would really heat it up.

Is "good enough for Australia" the same as "good enough for government work?"

[JetForMe]

The other part of this is that I tried the 80 mm fan, and it's just as loud! I also bought a 92 mm fan, and on the medium speed attenuator it is much quieter. But the fan mount in the 'scope is for 80 mm. Someone online has a 3D printed adapter, but it requires drilling out the press-fit-attached metal mount. I think instead, I'll mount the whole thing in my CNC mill and make new mounting holes. I’ll try to video that whole process.

[mwb1100]

A post about putting a variable speed fan controller into a Siglent SDS2000X Plus:

  - https://www.eevblog.com/forum/testgear/siglent-sds2000x-plus-coming/msg4597267/#msg4597267

Maybe a similar setup in the MSO5000 will make it so the fan is quiet until something gets hot enough to warrant a noisy fan.

[BRZ.tech]

Hi.
MSO5000: FAN x VENTILATION
This issue of internal ventilation in the MSO5000, in my opinion, is very critical.
The internal fan draws in external air, through the ventilation hole on the left side of the rear cover, and blows it over the electronics to spread the heat generated INTERNALLY by the components, and not to forcefully exhaust it.
But the MSO5000 does not have ventilation holes at the top and bottom of the back cover. And the hot air generated internally is distributed without forced exhaustion to the outside. Hot air cannot be exhaled by convection upwards from the rear lid.
The SMPS also generates heat, and does not have a fan.
In the MSO5000, air circulation is carried out naturally, without an exhaust fan, through the ventilation holes on the right side of the rear cover.
This happens if the user is in an intensely cold place all year round. The external temperature of the air that is drawn in will be cold, and this cold air, when it is blown over the components that generate heat, may be able to cool the MSO5000 from the inside.
If the external temperature of the air being drawn in is HOT (more than 30ºC or 303Kelvin), this HOT air, when blown over the components that generate heat, may be added to heat generated internally, and the MSO5000 heats up even more internally.

To do a quick test, to find out if your MSO5000 is boiling inside, use it for more than 1 hour, and then touch the BNC connectors with your finger, where the signal input probes are connected...
If they are hot, or a little hot. This will not be a good thing.
A symptom of exaggerated internal heat is that when using an analog channel of the MSO5000, suddenly, without being activated by the user, one of the other channels turns on the LED... and you have to turn it off manually.

You can compare the ventilation of the MSO5000 with the ventilation of the DHO814, as in Dave's video, here on “TEARDOWN”:


You can see the ventilation holes on the back cover, top and bottom. And also at the rear. Also the fan that works pushes the internally generated hot air, which are on the giant heatsink, and throws it out.
Perhaps the DHO814, under normal use condition, the internal temperature will be balanced. Although I think the fan is too small, for that size of heatsink.

Continues in another post.

[BRZ.tech]

Hi again.
As for replacing the original MSO500 fan, with a Noctua, it could be a good solution to reduce internal noise.
But it does not resolve the issue of internal temperature, the lack of heat exhaustion by convection, and the lack of forced ventilation to remove the hot air generated internally.
This issue of internal heat may shorten the lifespan of the MSO5000. And cause poor contact in electronic components, soldering, early failures, etc...

In my case, on my MSO5074, I understood that it is better to have more noise than to have high internal temperatures.
During the factory warranty, I thought it was best not to break the warranty seal, and to install an external fan, on the right side of the rear cover.
In this case, I took a common CPU-PC SMPS fan. It uses 12VDC, and is 10cm diagonal, and I use an external 12V power supply on the MSO5000.
The noise increased, but the internal temperature decreased a lot.
To attach the fan, you do not need to drill or damage the back cover. I attached 3 fan mounting tabs with 3 pieces of hard wire, with jacket, #12AWG. (see the photo).
When I turn on the MSO5000, I already turn on the external fan.
The external fan is located exactly over the internal SPMS, and can also suck in the hot air generated there.
I recently saw in another topic here on EEVblog, that the SMPS of the MSO5000 does not have a 12VDC voltage output:
https://www.eevblog.com/forum/testgear/rigol-mso5000-power-supply/msg4939123/#msg4939123

In the future, I intend to install internally, over the MSO5000's SMPS ventilation holes, a 5VDC fan, with the largest diameter and smallest height possible, to forcefully exhaust air through the holes on the right side of the rear cover.

An ingenious solution is RIGOL, remaking the mold of the rear cover, and placing ventilation holes in the top and bottom, and installing a forced exhaust fan over the SMPS of the MSO5000.
And, provide free of charge, under warranty or out of warranty, the new rear cover and the new fan, for users purchasing this MSO5000.
That's a lot of thinking and acting for an international manufacturer of measuring instruments.

[wraper]

Do not forget about static pressure spec. You can chose more silent fan that has similar airflow but it can turn out it will perform drastically worse because it cannot push the air through the heatsink or other obstructions.

[mabl]

You guys may be interested in https://www.thingiverse.com/thing:6556340.