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Siglent SDS1104X-E noisy fan replacement

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AdiGital:
It’s been a while since the last post but I hope this might be of use to some.

After a few months  |O I finally gave up and opened the scope. My idea was to measure critical temperatures and characterise the fan performance based on its voltage – when the scope is fully closed. I attached 3 probes (DS18S20) to the power supply heatsink, FPGA heatsink, and one “loose” inside the case. The probes are attached using double sided heatsink thermal tape, which is quite strong. Additionally, I placed one more probe a few cm from the inlet fan.

Next, I hooked up the SLA1016 logic analyser to give the setup more power draw. I also switched all channels, analog and digital on.
I programmed the SPD3303 to 5 1h slots. Started with 8V increasing it by 1V every hour. Below you can see the graph. I also attached the scope placement. There is not much air movement in the corner.

Looking at the data I take it’s safe to under-volt the fan. I believe I’ve read the operating temperature is up to 40 deg. Here in North-East England, where I live there is rarely above 25 deg outside. Plenty of headroom in my view.

I’m settling with powering the fan with 9V. The noise is much-much lower and bearable. I can barely hear it and it’s not annoying. Besides, it's easy to stick a standard, linear regulator without risking noise from a buck regulator.

I’m planning to do similar experiment with the SDM3055 and STD1062X soon. Can’t stand them fans!

P.S.
I just spotted a mistake. The last slot should be 9V.

pope:
Is there any chance that although the scope would be functional, the measurements won't be accurate?

Fungus:

--- Quote from: pope on March 15, 2022, 09:50:19 pm ---Is there any chance that although the scope would be functional, the measurements won't be accurate?

--- End quote ---

Nah.

People worry too much. I don't know about the Siglent but my Rigol DS1054Z was specified to work in ambient temperatures of 50 degrees Celsius so I didn't worry too much about the fan when I swapped it here in my 24 degrees room.

I don't imagine the Siglent's spec is much different.

Domitronic:

The SDS1104X-E has an operating temperature range from 10°C to 40°C. So not as much as the Rigol. But also more than a typical ambient temperature in most labs.

AdiGital:

--- Quote from: Domitronic on March 16, 2022, 07:23:13 am ---
The SDS1104X-E has an operating temperature range from 10°C to 40°C. So not as much as the Rigol. But also more than a typical ambient temperature in most labs.

--- End quote ---

Looking at my chart, when the fan is on full blast (12V) FPGA heatsink is about 31°C above room temp (26°C). Applying that to the max operating temp of 40°C it's safe to assume FPGA at 70°C should be OK.

Yesterday I had it all day on 9V with the logic probe attached and it never went above 63°C. So by limiting the fan voltage I lowered the max operating temperature by 5-6°C (12V=57°C -> 9V=62°C). OK, giving a huge margin, let's say 10°C.

If I ever have 30°C in my room I won't be playing with the scope and be outside with a frosty glass of beer in my hand  ;)

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