Logitech X-140 speakers buzzing is it normal?

[basskilla]

Hi There!

I bought secondhand Logitech X-140 speakers,it is old but it think the quality is all right.
My problem it has background buzzing noise even if nothing is connected to it.
It is not too loud,but if the room is quiet,it is noticeable.

if I touch the metal cover,or the tone knob the noise is louder,I have the plastic cover knob,but I don't know is this noise normal or not.Sounds like a grounding issue or something like that.

I tried to resolder the jack connection but nothing changed.

Here is a little video about the speakers:



https://www.youtube.com/watch?v=8hEqiBs-f7w


Is it a normal behavior of the speakers?If it is not,how can I fix it?
Thank You for Your reply!

[petehall347]

Re: Logitech X-140 speakers buzzing is it normal?

not normal

[basskilla]

Re: Logitech X-140 speakers buzzing is it normal?

not normal

Thanks,any suggettison or tip to fix it?

[momaka]

Re: Logitech X-140 speakers buzzing is it normal?

Open them up and post some pictures.
Could (very likely) be the power supply filter cap(s) gone bad.
I don't see a power adapter with these, so that means the power supply is in the speaker boxes. Not sure if it's oldschool AC line traffo or new SMPS design... but either way, this smells like bad caps problem to me.

Also, do make sure to use them with the plastic knobs on there. The reason the sound goes louder is because you're coupling stray AC mains picked up by your body to the electronics inside. Hence the AC hum you hear.

[basskilla]

Re: Logitech X-140 speakers buzzing is it normal?

Open them up and post some pictures.
Could (very likely) be the power supply filter cap(s) gone bad.
I don't see a power adapter with these, so that means the power supply is in the speaker boxes. Not sure if it's oldschool AC line traffo or new SMPS design... but either way, this smells like bad caps problem to me.

Also, do make sure to use them with the plastic knobs on there. The reason the sound goes louder is because you're coupling stray AC mains picked up by your body to the electronics inside. Hence the AC hum you hear.

Thanks for Your reply!

Here are some pictures about the power supply and the amp board.

The plastic knobs are on but the noise still noticeable.I tried to bypass the factory adapter and swap with an external one but the buzzing-hum still persists.

[Th3_uN1Qu3]

Re: Logitech X-140 speakers buzzing is it normal?

YES. A bit of hum and buzz is normal.

All PC speaker systems have basically been designed and built with ground loops/ground faults from day one, and age on the capacitors and passives only makes it worse.

[keklikelektronik]

Re: Logitech X-140 speakers buzzing is it normal?

hi.sound have some parazites.you can change the capacitors.

[petehall347]

Re: Logitech X-140 speakers buzzing is it normal?

there are some dodgy looking solder joints that need attention . especially 1 next to R3

[basskilla]

Re: Logitech X-140 speakers buzzing is it normal?

hi.sound have some parazites.you can change the capacitors.

Ok I will change the electrolytic capacitors.Do You suggest to change the ceramic ones also?

[CapLeaker]

Re: Logitech X-140 speakers buzzing is it normal?

No. Only the electrolytic ones.

[R_J]

Re: Logitech X-140 speakers buzzing is it normal?

Changing caps is not going to fix this issue, The case and controls should be at ground potential and they are not, likely a broken ground wire (shield in cable) between the speakers and the source, Check that Black wire with the red, white and shield