Radio Like Buzz from left channel

[newtoCaps101]

So after my old set of speakers broke I was given a small set of speakers from a friend, they have served me well for the last 6 months but now the front right channel has started tiny radio like buzzing noise when when nothing is playing or the volume is all the way down. I have swapped speakers but it it happens with the other speakers on this channel as well. So definitely not speakers but the amplifier circuitry inside the sub woofer.

I opened the sub up, everything looks fine, I am thinking a dry joint or maybe a ground loop? What should I be looking for??

[budm]

Re: Radio Like Buzz from left channel

No make and model number? Pictures? Make sure to upload pictures using attachment function.

[newtoCaps101]

Re: Radio Like Buzz from left channel

they are small cambridge speakers, here's some pictures, it will show make model number and everything.

edit: some noise and buzzing goes away when I touch a heat sink with a screw driver with my hand on the metal, thus grounding it a bit)

[budm]

Re: Radio Like Buzz from left channel

That is conductive brown glue on the input board, it is corrosive and conductive, I can see it on the ribbon cables which carry the audio signals. Is the glue also on the main board?

[newtoCaps101]

Re: Radio Like Buzz from left channel

Its not on the main board but they put this crap glue all around the sister board. It cant be the glue since it worked fine all this time, I think something gone bad maybe a cap or a lose ground connection? an suggestions?

[budm]

Re: Radio Like Buzz from left channel

Yes, it can be bad ground, but as glue gets older, it will conduct signals (I had problem with cross talk due to glue on the ribbon cable on the multi-track recorder, we are talking about signal in the mili-volt range). But you have indicated that the noise is still present when the volume is all the way down, so it must be in the circuit after the volume control. Where is the volume control located at, at one of the speaker?

[newtoCaps101]

Re: Radio Like Buzz from left channel

Yes the noise is like an old radio buzzing that can be heard about 1 feet close to the speaker, it is still there even after the volume nob is all the way turned down to 0. It has a separate volume control that connects the rear of the sub using 2 3.5mm cables(Front out and Rear out). Have a look at the image. You think its the pod?

[budm]

Re: Radio Like Buzz from left channel

That volume control is more likely to be variable DC voltage for controlling the electronics volume control circuits on the main board, it is done that way so the wires to pot will not be affected by picking hums and noise on the long wires to the Volume pot, it will only need 3 wires instead of 9 (8 audio, 1 common ground) wires to control 4 amplifiers. I can only see two IC power amps (2 2-ch per IC amp), but it has 5 speakers total, so I do not know what the setup is yet.

[newtoCaps101]

Re: Radio Like Buzz from left channel

It has 4 satellite Speakers & a sub. So I think one IC is for the 4 Speakers and the other for Sub. should I re solder the IC's and other joints?