Two bad PSUs in a row?

[Synomenon]

Got my second SilverStone ST65F-G today. This new ST65F-G has the exact same issue as the first. An annoying high-pitched squeal / buzzing noise.

The noise happens randomly, but frequently. I've tried plugging the ST65F-G into different power outlets in my house, my friend's house and at work and even to an automatic voltage regulator. I've tried it in three different computers as well. I also did all of this with the previous ST65F-G.

Keeps making the noise as long as it's plugged into power outlet and the power switch on the back is on.


Is it possible that I've received two "bad" units in a row?

I like the ST65F-G because of its compact-ness (140mm depth, 150mm width) which makes it easy to put into my BitFenix Prodigy. I don't think I could get any other modular PSU in there.

Here's a recording of the noise:
https://www.dropbox.com/s/20o5ds1fv8wwmmz/ST65F-G Squealing.m4a

 

[MicahC]

Its very possible to get two bad psus (or anything) in a row. lets say it has a 3% defective rate, (I'm making up numbers) meaning 3 out of every 100 are bad. if you send in for a new one, you still have that 3% chance, so 3% is not unreasonable. (they are independent events which is why it works like this).
As for the problem you had, the sound wasn't wanting to work for me, so I can't help you there.

 

[lehtv]

lets say it has a 3% defective rate, (I'm making up numbers) meaning 3 out of every 100 are bad. if you send in for a new one, you still have that 3% chance, so 3% is not unreasonable. (they are independent events which is why it works like this).

They are independent events, but the moment you look at the probability of getting two bad PSUs in a row, the pair of PSUs becomes your independent event. The probability of getting two bad ones in a row is 0.03 * 0.03 = 0.0009 = 0.09%. The other possibilities are bad * good = 0.03 * 0.97 = 0.0291 = 2.91%, good * bad = 2.91% and good * good = 0.97 * 0.97 = 0.9409 = 94.09%. Adding all these together you get 100%.

 

[Synomenon]

You can use Quicktime to play the audio file.

 

[MicahC]

They are independent events, but the moment you look at the probability of getting two bad PSUs in a row, the pair of PSUs becomes your independent event. The probability of getting two bad ones in a row is 0.03 * 0.03 = 0.0009 = 0.09%. The other possibilities are bad * good = 0.03 * 0.97 = 0.0291 = 2.91%, good * bad = 2.91% and good * good = 0.97 * 0.97 = 0.9409 = 94.09%. Adding all these together you get 100%.

yes you are right if we do not know whether or not the first is bad, but I assumed we were only interested in the probability that the second is bad IF the first is bad. right?

 

[lehtv]

I was just clarifying that it wouldn't be a 3% chance for both PSUs to be faulty in a row. It seems to me though that if the second PSU is faulty, and the first one had the same symptoms, then both were probably faulty. I know that doesn't exactly solve the OP's problem but still

Also the chance for both PSUs to have the same fault could be a lot higher. High pitched squeal may not be as uncommon as DOA, for example. Coil whine has been a common complaint in some units such as Seasonic X650. AFAIK it doesn't affect the unit's stability, it's just annoying.

 

[Synomenon]

So from my attached audio file, can you tell if that is coil whine?

 

[lehtv]

No, doesn't sound like coil whine to me... Coil whine would be more constant. It's weird