Audio Hum out of only Right Channel of System

[0kazaki101]

I recently got a hold of a cheap beFree Sound BFS-440 5.1 Channel Surround Bluetooth Speaker System.

After a few weeks of the unit working completely fine, there came a day where an audible 60hz hum started coming out of both right speakers (front and back). The first day it started, it wasn't bad. After around 2-3 days, it got to the point to where I had to stop using the right channels all together because the humming got so loud and obnoxious.

I've done a little bit of troubleshooting, and here is what I have done.

• Unplugged the whole system and put it on a different circuit in the house. Same hum.
• Plugged different speakers into the outputs making the hum. Same hum.
• Took the unit apart in order to see any incorrect grounds. Nothing. Same hum.
• Tried selecting different inputs. Same hum throughout each input.
• Tried changing the volume to see if there was a problem with the amplifier or inputs. Same hum without getting louder or quieter.
• Removed all inputs. Same hum.

After reading many reviews (something I should've done earlier) I have found that this problem happens frequently with this unit.

What I am asking is this:

• What could be causing this hum?
• Why is the hum only coming out of one (or two) channels?
• Is there a way to fix this hum?
• Are there additional steps on troubleshooting that I can do to isolate this hum better?

After researching a bit, I have come to the conclusion that it is possible that the transformer inside the unit is to blame for this hum. I have also seen that a faulty bridge rectifier could be to blame. But this only makes sense to me if all of the channels are humming.

Any thoughts?

 

[avionic]

Hmm... Welcome to AK. I'm guess you won't be buying anymore befree ,ahh "stuff" anymore.

 

[avionic]

• Why is the hum only coming out of one (or two) channels?

• Is there a way to fix this hum?

Likely a bad solder connection or a bad electrolytic capacitor in the offending channel. Yes its always fixable. Its going to cost you more than you paid for it for someone to repair it.I really doubt there is a service manual or schematic available.

 

[0kazaki101]

I don't have a schematic, but I can possibly make one. It is only a one sided circuit board with a slightly more complex daughter board (presumably for the bluetooth connections) on it. I'll try to post some pictures of the main board, daughter board, inside the chassis, and a homebrew schematic. So because of it only being one or two channels, you think it's a problem with the capacitors (or at least one of them)? Sounds easier and better to fix than the transformer.

Also, is there a good way to check and see if a capacitor is bad? I know the blown or bulging caps, but is there something I can do with a multi-meter in order to test them?

 

[avionic]

I don't know.. Have to see some good photos.

 

[zebulon1]

A good visual check of the boards with a magnifying glass maybe all you need.