PSU Knocking/Rattling

[weegee15]

Cooler Master MWE Bronze 650w

 

On a cold boot, the PSU makes a weird knocking sound, rather strangely when it's in silent mode (fan off).

When the fan starts spinning (eg. stress test), the knocking sound goes away.

I think it could be temp related, since it only does this on a cold boot.

It's a couple months old.

[Windows7ge]

Could be coil whine. Not all manufacturers honor coil whine as a reason for RMA. If that's what it is you may be SOL until such time that the PSU malfunctions.

 

Is this knocking fast? Slow? Rather high pitch? Low tone?

[weegee15]

1 minute ago, Windows7ge said:

Could be coil whine. Not all manufacturers honor coil whine as a reason for RMA. If that's what it is you may be SOL until such time that the PSU malfunctions.

 

Is this knocking fast? Slow? Rather high pitch? Low tone?

It isn't coil whine, I've verified that.

Knocks fast and a low tone. 

 

Might get a recording, if necessary.

[SpookyCitrus]

The knocking when in silent mode could be something trying to kick the fan on but since it's in silent it can't, could be a defect because it goes away when not in silent mode.

[Windows7ge]

Just now, weegee15 said:

It isn't coil whine, I've verified that

Knocks fast and a low tone. 

It could be the fan. 0RPM mode doesn't necessarily stop power from going to the fan it just drops it to a level where the fan stops spinning. Fans need a certain amount of power to start rotation but once rotation starts they can run at a voltage lower than where it started spinning (centrifugal force).

 

When power is close but not quite high enough to start a fan spinning it will bump the fan. When the fan bumps you can usually see it twitch. Which it does this it can make an audible low tone knocking sound.

 

It could be this. Have you looked at the fan while the PSU knocks? Any apparent twitching?

[weegee15]

Just now, Windows7ge said:

It could be the fan. 0RPM mode doesn't necessarily stop power from going to the fan it just drops it to a level where the fan stops spinning. Fans need a certain amount of power to start rotation but once rotation starts they can run at a voltage lower than where it started spinning (centrifugal force).

 

When power is close but not quite high enough to start a fan spinning it will bump the fan. When the fan bumps you can usually see it twitch. Which it does this it can make an audible low tone knocking sound.

 

It could be this. Have you looked at the fan while the PSU knocks? Any apparent twitching?

Very very very slight twitching

[Windows7ge]

1 minute ago, weegee15 said:

Very very very slight twitching

Then the fact you only hear this when the fan isn't spinning and you've verified it isn't coil whine then it's probably from the fan. Does the PSU have any fan switch where you can force it to always  run?

[weegee15]

3 minutes ago, Windows7ge said:

Then the fact you only hear this when the fan isn't spinning and you've verified it isn't coil whine then it's probably from the fan. Does the PSU have any fan switch where you can force it to always  run?

No. I've heard that it might be because of C1E and EIST. Is that true?

 

[Guest]

It's the LLC controller in burst mode while the load is < 10%.

 

They all do this.

 

http://www.deltartp.com/dpel/dpelconferencepapers/APEC 14 LH_Audio Noise.pdf

 

 

[weegee15]

On 7/27/2020 at 9:29 PM, jonnyGURU said:

It's the LLC controller in burst mode while the load is < 10%.

 

They all do this.

 

http://www.deltartp.com/dpel/dpelconferencepapers/APEC 14 LH_Audio Noise.pdf

 

 

Basically, I can't do anything about this, correct?

 

 

[Guest]

7 minutes ago, weegee15 said:

Basically, I can't do anything about this, correct?

 

 

If you're positive it's not the fan... probably not.