Beomaster 4500 IR Noise/Buzzing

[jacope]

Hi all,

I have a Beomaster 4500 (type 2963, SW 1.6) and Beolink 7000. Every time I press a button on the BL7000, I get a pretty loud and definitely noticeable buzzing noise through the speakers. Just a pulse, not a sustained noise. Happens on both Powerlink and Speakerlink. I noted that this issue does NOT occur when using a Beolink 1000 or BEO4 , which makes me think it has something to do with the IR Transmitter section. I replaced a blown 10uf cap (5C110) which I was hoping would solve the issue, but it remains. Couldn’t find anything else of note on PCB5, other electrolytics tested good. Fixed a few dry joints but they were not relevant to this circuit.

Has anyone seen/fixed this problem? Any ideas would be great, thanks!

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[jacope]

I have also confirmed with my phone cameras that the noise occurs every time the 4 IR transmitter LEDs flash. The noise does not change with the speaker volume – always the same, even at zero.

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[Madskp]

I think I know the buzzing noise you are mentioning. When I have had issues with this it has been related to datalink issues, in some cases experimental cable connections.

So a hint could be to disconnect everything that is datalink connected (which also counts Powerlink and MCL connections) and check for loose connectors. Also maybe connect things one at a a time to see if a specific device trigger the buzzing.

Hope this can lead to a solution

Btw. you mention SW 1.6 in the BM4500, but to my best knowledge that should not work with two way remotes, but I might be wrong.

Location: Denmark

[jacope]

Interesting. I’m using a Beosound Core for testing (RJ45-DIN) I’ll try some different sources and connection types.

I found the same thing online, yet this one definitely states 1.6 on the back sticker, and has both IR receiver and transmitter on PCB5. It does not have the extra IR that shines through the glass panel like later versions did.

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[jacope]

Alternatively, is there a way to disable 2-way communication? I’d like to use the BL7000 for control but don’t necessarily need the feedback from the BM4500. This would eliminate the noise as it only happens when transmitting.

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[Madskp]

I belive the hardware for the two way is there even though the software is not ready for it ( bonus info: instead the 1.6 SW will let the BM4500 work as a link room).

That said the two way functionality might still do something even though the software is not complete, which is prooved by your IR transmitter flashing (unless its because you actually have a newer software in it). And that might activate some signaling on the datalink part.

Regarding disabeling of the two way. As far as I know the BL7000 decides if it is one way or two way when you register components in the setup menu on it. How that works if the product is partly capabale of two way I dont know.

 

 

Location: Denmark

[lausvi]

Madskp wrote:

Regarding disabeling of the two way. As far as I know the BL7000 decides if it is one way or two way when you register components in the setup menu on it. How that works if the product is partly capabale of two way I dont know.

Perhaps using the BL7000 in a place where it can’t reach the BM (fe. other room) and re-registering the audio master would make it operate in one-way (into the BL)?

Using the BL7000 in one-way mode is very clunky though.

Location: Helsinki - Finland
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[jacope]

Popped the shield off of PCB4 to discover that the actual software on the chip is 2.2. Must have been updated at some point. Regardless, no change using different connections and inputs. Still buzzing. Haven’t found any faulty components or incorrect voltages around the transmit circuit.

Electrically, what could be causing the noise? Something spiking the voltage when the emitter diodes are flashed? Grounding issue somewhere? When I received it, there was a bad rectifier diode (D19 – IN4002) and a blown fuse. Could this be related?

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[jacope]

Some speculation here as I am not an electronics engineer:

I figured it was some kind of grounding issue. 5C110 takes the transmitters directly to ground – the original was a 10uf cap that was blown in my case. I tried some iteratively larger caps and found that the buzzing was getting quieter above 100uf. I stopped at 470 which does not completely eliminate the noise but you don’t notice unless your ear is to the speaker. I am not sure if this will have any ill effects in the long term but I have not seen any change in operation since swapping for a larger cap. I assume something like 1000uf might completely eliminate the noise, but again I am not sure if this change will affect any other function.

Works for now!

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[Madskp]

I am no electronics engineer either, but I was thinking what about the other caps that are in parallel with C110 like C105 on the same PCB and C101 on PCB 3. Have you checked them? If their properties are out of spec that might affect the total capacitance in the circuit.

Location: Denmark

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