WF-139 Buzz/Hiss when "not" charging

Is it normal for this charger? It makes a noticeable buzz/hiss sound when the light is green and not charging. Upon charging (red light) the sound is gone. It charges fine to 4.20v though, from what I can tell. Just curious is this normal for these or likely mean a bad electrical component.

thanks!

Try the charger at work or a freinds house to rule out dirty utility power.
You could also try plugging it into a smart UPS to see if that may be the cause. Just a thought for you to rule out.
GL

llmercll said:

Is it normal for this charger? It makes a noticeable buzz/hiss sound when the light is green and not charging. Upon charging (red light) the sound is gone. It charges fine to 4.20v though, from what I can tell. Just curious is this normal for these or likely mean a bad electrical component.

thanks!

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As a fire safety precaution, I always unplug these chargers when not in use. They work well enough for me and I use them, but being from China, and being a *fire brand, I'm a little more suspect of them.

I'd say you're ok, just keep your eye on it, don't leave it unattended.

My PILA IBC whines when plugged in and not charging anything, it's how I know my batteries are done.

I plugged the AC adapter into the wall without the charger attached and the whine persists, so I imagine it's probably just an inductor vibrating when not put under load or something. Hasn't caused me any problems just yet.

Hopefully yes, it is a normal sound like the inductor. But, I have heard cracked circuit boards arcing sound like this too. My instincts tell me it is the high voltage side transformer. Although I am not sure why it would only do it when not charging. But no, I don't think it is normal.

Most likely normal, cant say about that specific charger, but on PWM circuits in general, under light load like that, it may go into "pulse skipping" where rather then a constant 50+ khz frequency, the SMPS stops oscilating as long as the voltage is within tolerance. This off-on cycling may occur in the audible band, making the noise you hear.

Some flashlights do something similar to this, if the driver runs at some inaudible frequency, but the PWM dimming runs at 500 hz (plenty fast for there to not be flicker) you could hear the inductor or other components humming, usually a bit louder as you dim the light.

My cell phone charger also hisses some when its hooked up to the phone and charging is complete too, now that I think of it.

Thanks for the replies,

Can anyone who owns this model testify that theirs does/doesn't do the same thing?

thanks!

Unless you're super sensitive to it, I wouldn't say mine makes much of a noise at all when charging or not. I had to put my ear right next to the charger (nearly touching) to detect any noise at all. It sounded more like the slight hiss you get from speakers than a buzzing noise. When I lifted my ear, nothing. Now my room isn't perfectly quiet or soundproof, but I can't imagine you would be bothered by the noise mine makes. I purchased it recently from Lighthound if that makes any difference to anyone.