ARCHIVED FORUM -- March 2012 to February 2022READ ONLY FORUM
This is the second Archived Forum which was active between 1st March 2012 and 23rd February 2022
dear all,Our B&O Beomaster 7000 generates a buzzing noise (sounds like white noise) that is so omnipresent that we can even perceive it at a moderate volume.we've opened it and noticed that the mixer-unit is equipped with numerouns electrolytic capacitors which are certainly not as fit (may have dried up causing their nominal value to be quite offset), which react on contact with a 50Hz hum (which is audible via the attached active speakers).sometimes the sound disappears, but if you continue using the remote (beolink), eg by adjusting the volume, then the noisy carpet pops back in and stays even if the remote is put aside ....
this kind of high pitch noise is present regardless which input channel is selected, i.e. CD, TV, satellite, radio, etc, (even if only the CD-hub is connected). with the tuner (integrated in the beomaster), this buzzing noise appears to be less present.my question:i) does anyone have a serivce manual for the beomaster 7000 series (incl. beogram 7000 & beolink 7000)?i) should I replace the capacitors straigh away?
would be grateful for any advice
thanks Piero
Piero,
Welcome to Beoworld !
Whereas the preamp capacitors may be fit for replacing, they usually don't introduce noise. Insteadthey can make the programme sound dull and less detailed or even block a channel completely.The symptoms you describe makes me think that the problem is to be found with the decouplingof the power supply for the preamp.There are some small capacitors, about a handful or so, and I've seen them cause "digital" noiseacross the signal when they no longer do their job properly.
The service manual is available for download from our main website, a minimum membershipof silver is asked for.
Martin
If you're planning to use the master for the next few years, then you can replace the capacitors straight away.
Several 10uF caps and other in the powersupply need to be changed. But if that is the solution for your buzzing noise, time will tell.
Check dry/broken solderings on the vertical input board. Also check the rest of the mainboards. The Fm board (upside placed board on top) is not the culprit.
BTW change both relais, they're most probably causing bad contacts. Trimmers are also a good idea to change. Take out the front and clean the ir-leds and the axial placed caps.
Martin writes faster....
dear Martin .... thanks for the prompt reply and the suggestions - will do so asap - with appreciation Piero
g'day beobuddy .... your suggestions sound simple .... will have this done asap along with a thorough check for "cold" connections of the boards .... thanks Piero!
Just curious. What outputs are you using? I've never noticed anything like this on the Powerlink or headphone out of my BM7000, but I've never used the Speakerlink outputs on it. The only thing I've noticed on my 7k is that when it is EXTREMELY quiet and you are turning the volume or bass/treble up and down you can hear a very faint "tick" through the speakers each time you go up or down one notch on the bass, volume or treble controls.
These ticks are caused by the interference of the data via the powerlink. What speakers are you using with the BM7000? Penta's? A modification was released to avoid that.
These ticks are for me less irritating than the "blob" the penta makes when swichting on. But also for that is a solution I did years ago. Only the clicks of the relais is heared when switching on or off. Much better. But that's a bit off topic.
Beobuddy: These ticks are for me less irritating than the "blob" the penta makes when swichting on. But also for that is a solution I did years ago. Only the clicks of the relais is heared when switching on or off. Much better. But that's a bit off topic.
Beobuddy, is that mod described in the old forum? I tried to find it but couldn't. Would you be so kind as to post a link?
OP, sorry for the thread jack.
Thanks!
/ Johan
Interestingly I have the BM7000 connected to the BL5s via the *headphone* jack and a 3.5MM to RCA jack cable right now because it's just a temporary setup and I don't have the right PL cables for the BL5s at the moment. I'm pretty sure I hear those ticks through there too but I may be wrong. And keep in mind these ticks are extremely faint, it's not like that one bad BS9000 I had with the horrendous "pops" every time you would switch an input, mute it or turn it off.
The ticks can come from the digitally controlled volume/tone control and, as such, will be present on all outputsdownstream from the volume/tone control.
Imagine a nice round sine wave where, at some point the volume (programme signal amplitude) is suddenly changed a bit.This causes a close-to-vertical piece of waveshape to be introduced to the signal.In other words, this breaks the continuity of the wave and you can hear it as a soft click.Ideally, with no signal input and volume at zero, there should be no click to be heard (since any factor times zero willstill be zero), but it's not always so in real life since the programme signal doesn't always necessarilycenter around zero volts. It depends on the circuit construction and the general component state of the unit.Some units will click more than others.You will almost always be able to hear a soft click when changing the sound settings on digitally controlled units unlessthe units were developed (expensively) to only apply the change at points where the signal crosses the zero voltage line.
The Beomaster 8000s volume control is particularly prone to click and here adjustments are provided to minimize it.It will never go away completely though.