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ARRAY electronic loads

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MarkL:
I have a 3723A, which is in the same product line, so I'd expect it to have a similar internal build as the 3721A.  The fans are noisy, and they also have the same "rubbing" or buzzing sound as in your video.  It's hard to tell, but yours might be a little louder.

I would take the cover off and check for anything obvious in the way of the blades.  There are two fans, at least in the 3723A, so try disconnecting one at a time to see if one of them is the culprit.

Test equipment manufacturers aren't generally looking for the quietest fans when spec'ing their parts.  You could always replace them with quieter fans with the same rating if it continues to bother you.  It might be a little work getting them out, though, since they're inside the metal air duct around the heat sinks.

Or, since it's new, you could ask for a swap for a different unit.

(Edit: Fix ambiguity.)

saturation:
I think this is a teardown of this model lie from an archived post:

https://www.eevblog.com/forum/testgear/any-experience-with-scpi-and-chinese-dcprogrammable-loads/msg352717/#msg352717

@ MarkL, is this correct?

IIRC, the fans are on continuously in this model line?



--- Quote from: sacherjj on September 23, 2014, 01:17:23 pm ---
--- Quote from: DaGlitch on September 23, 2014, 05:17:46 am ---Just got a 3721A and was wondering if anyones unit sounds like mine. I can hear the fan just fine, but this sounds like something else. I didn't see any mention of the noise anywhere (or expected it) so I thought I would ask to see if this was normal. Cheers!


--- End quote ---

That sounds like maybe a fans running while rubbing on something.  The 3710 has two stages of fans, but they come on full, half, off cycle when powering.  So it doesn't seems like the sustained sound would be there if it was the fan.  Unless the control circuitry is messed up.

Although the insides of the 3710 and 3721 might be completely different.

--- End quote ---

DaGlitch:
Took the unit apart and it is definitely the fans. They aren't rubbing on anything and are just noisy. I can stop both of them and the unit becomes completely silent.  Inside my unit:

saturation:
Thanks DaGlitch for that photo, it does look like MarkL's teardown device so the other images are from the same model line.

MarkL:

--- Quote from: saturation on September 23, 2014, 06:20:15 pm ---I think this is a teardown of this model lie from an archived post:

https://www.eevblog.com/forum/testgear/any-experience-with-scpi-and-chinese-dcprogrammable-loads/msg352717/#msg352717

@ MarkL, is this correct?

IIRC, the fans are on continuously in this model line?

--- End quote ---

Yep, that's correct; those are my pictures.  Sorry; that's not really much of a teardown.  I was mostly answering a question about the built-in isolation.

The fans are always on in the 3723A, and they really get cranking if it gets hot while sinking a lot of power.

The unit, at least as supplied with the stock fans, is definitely not for those who want it quiet in their lab.  It doesn't bother me because there's already so much other stuff running.

It might be hard to find a very quiet programmable DC load that can handle a decent amount of power.  It has to dump the heat somewhere...

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