RCF ART300A Buzzing

[Kenny Powers]

Hi Guys,

I am new on here looking for some advice, I have 2 Active RCF ART300A Speakers they are probably about 15 years old at this stage.

One of them has developed a constant buzzing when powered up even with nothing connected and the input level turned completely down.

The only solution I found to minimize this is to run a wire form the ground post on the back of the speaker to the ground post on the mixer, Once they are connected the buzzing is gone (Again this is before I connect the mixer to the input) The other speaker has no issues.

I had a look inside at the amp I couldn't see and dry joints or bulging on the Caps.

Has anyone here come across this before? Can anyone shed some light?


Thanks

 

[ianpengelly]

Sounds like there is an issue in the audio ground, perhaps a dry joint (not always visible) at the input to the pre or power amp stages. Is it an all in one board?

 

[Kenny Powers]

Hi,

There is a small input board on the side with XLR inpus and volume controls, when you touch this or move it the buzz varies but I swapped it with the working speaker and there was no change.

The rest of the Amplifier assembly is all on the one board.

 

[Kenny Powers]

Here is a couple of pictures, I have the service manual and schematics as well.

Main Board

Input Board

Main Board PSU Section