Buzzing Makita DC1414 F charger

[Cirkit]

I have the above Makita charger which is buzzing with a variable frequency when the green LED flashes.

I have tried prodding the transformer and various components but the buzzing doesn't stop.

I don't want to start replacing capacitors on the chance that may cure the buzzing.

Attached are photos and a video showing the buzzing can be downloaded from this link:

https://ufile.io/v78dr3o2

Any suggestions on where I should start looking?

Thanks.

 

[Martaine2005]

Hi CirKit,
The free (slow) D/L doesn’t work.
Can you describe the buzz?.
Is it only when the LED flashes?.

Is it definitely a buzz rather than a high pitch tone?

Martin

 

[Harald Kapp]

Download worked for me.
It is a medium to high pitched sound (similar to an electric razor, but not so loud). The frequency changes with the blinking of the LED: LED on -> frequency high, LED off, frequency low. Notable peaks are around 4 kHz and 6 kHz:

 

[bertus]

Hello,

@Harald Kapp @Martaine2005 , I see that the free software Audacity is used to show the spectrum of the sound:
https://www.audacityteam.org/
It is a rather strong package with a lot of capabilities.

Bertus

 

[Martaine2005]

It sounds like the caps aren’t doing their job. Given the stresses these caps go through in SMPS, they are also the first components to fail.
I would replace them as a matter of course.

Martin

 

[Cirkit]

Thanks for uploading the spectrum @Harald Kapp.

@Martaine2005 do you have any suggestions which capacitors I should replace? Is it likely to be the main filter capacitor?

 

[bertus]

Hello,

The mains capacitor could cause hum.
The output capacitor could cause screeming (high frequency noise), when the ESR is going up.

Bertus

 

[bertus]

Hello,

When you change the fourrier size and look at the spectrum, the 100 Hz is good visible:

You will also see signals at 4000, 8000 and 12000 Hz.

Bertus