Beomaster 7000 with Penta buzzing noise

[Marto]

Hello everyone , I’m looking for help with a case that I’ve been struggling with for a long time. I have a Beomaster 7000 and a Beolab Penta. Everything has replaced capacitors, as well as some other elements such as operational amplifiers, etc. according to instructions on other topics from the forum. The problem that bothers me is some kind of buzzing noise that is emitted as soon as I press a button on the beolink 1000. I know that it is connected to the Datalink via the powerlink cable (mine are mk2), but I don’t know how to treat this problem. It’s not the cables, I tried different ones. I hope someone can give me some guidance.

Martin

[TK]

When you say “buzz” do you mean a low level “bzzz-bzz-bzz” type noise that may sound like someone is sending Morse code over your system?  If it is a low level bzz-bzz sound, does the length of the buzz vary depending which button you hit (advance vs selecting a new source, for example), or the component you use?   Does it also happen in between songs on it’s own?  If yes, then it’s likely your Pentas picking up the Datalink ’86 chatter being broadcast from the BM on Powerlink, used to update the Penta displays, as you surmise.  I’ve got a similar setup with the same symptoms, and I also have not fully worked out a filtering solution.

[Marto]

Yes it is absolutely the same buzzing, like You describe it. I also think it’s something with information needed for the display, because when I click on for example volume up first hear a “buzzz”, after a second or two in exact same moment of display changing I can hear buzz-buzz.

[TK]

IT definitely is datalink.  I’m writing a program which monitors and decodes datalink, and I can watch on my monitor as it is sent across the system, coinciding with all the buzzing.  Some system updates from a CD player transmit a bunch of data, while phono updates are infrequent. I don’t have a strategy for removing it yet, unfortunately.

[jacope]

I solved this issue a while back on a Beomaster 4500. Very different setup but the issue was the same: any button press with remote comes out as a buzz through speakers. In my case it was actually the IR transmitter secction causing the buzzing – confirmed by switching to a one-way remote. Perhaps the BM7000 always transmits, even when using a one-way remote. Regardless, I swapped a capacitor in the transmit circuit for a much larger one, and it quieted down the buzz. Perhaps it could be something similar but somewhere in the datalink circuit.

https://forum.beoworld.org/forums/topic/beomaster-4500-ir-noise-buzzing/

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[Marto]

Thanks for guidance to this diodes. On Beomaster 7000 it’s 9C20 – 10uf capacitor on the same position like your 5C110. In service manual for 7000 this capacitor is grounded to “signal ground” and maybe this is the case here. I think maybe first to try just to disconnect the minus leed of the capacitor and will try to grounded on the other ground piont with a short wire to see what will be the result. What do you think?

[jacope]

Could be worth a shot, I dont have any feedback as to whether that will work or not. There was an immediate change with replacing the capacitor, and a larger cap produced a more quiet buzz. In my case 470uf took out 90% of the buzz. Your case may be different since its a different model, so you’ll have to tinker with the idea

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