Beomaster 7000 audible ticks when display changes value

[kees.de groot]

Hello all, what a treasure this forum is!

I recently acquired a Beomaster 7000 in great condition with a pair of Beolab 9’s. It sounds great and works well in combination with the cassettedeck and CD player 7000. However, I noticed that when I change the volume a tick can be heard in the speakers (during low volume passages, or without any music playing). I think it has to do with the display lighting up, as it seems to be ever so slightly louder when an “8”is displayed versus e.g. a “1” (the more segments light up, the louder the tick). Is there any way to fix this, for example by replacing capacitors?

I have already changed the trafo from 220 V to 240 V and that reduced the heat output. I’m planning to replace the filtre-caps and the two relays. I’m wondering if I should take any other capacitors into account (perhaps in the front panel?)

Thanks in advance, hoping to get some input!

—Kees

[TK]

Possibly sounds like you are hearing the datalink signals that are sent via the powerlink cables to alter the display on a datalink-enabled speaker. How about when you change the source input – does that also create a “buzz-buzz” sound?

Just to geek out a bit – The electrical pulses (representing the inverse binary of the number) are picked up by the music signal in cheap wiring. Interesting that “8” is louder than “1” – probably has to do with the signal pattern.  In the actual signal, “8” would be a bitstream of “0111” and “1” would be represented as “1000”.   I’ve read that buying higher quality shielded cables helps with the problem, but it could also be a fun project to alter the datalink transmission protocol via a series of dongles so the datalink signal is sent via some other means, perhaps over WiFi.

• This reply was modified 3 weeks, 3 days ago by TK.

[kees.de groot]

Hi TK,

That sounds rather interesting indeed! I have decided to recap the BM using the kit provided by DK Sound Parts, I’ll see if that changes anything. The PL cables I have currently in use are made by B&O and are (I think) the MKII kind: they’re quite slender plugs (tiny Bang & Olufsen logo) with a thin cable. Should be the shielded kind. It should work, considering they are original cables! Changing source does not give the same ticks.

I can follow your reasoning as to why and how the pulses may be the cause. However, changing the bass/treble levels (and thus displaying different values on the display) gives the same ticks. Would you say the bass/treble information is also transferred to the Beolabs through Datalink the same as the volume level? In that case I had no idea the speakers were managing the EQ and not the pre-amp in the BM!

best, Kees

 

[kees.de groot]

I just checked and when I switch SOURCE from AUX to TAPE (BC7000 switches on), the tick is also audible. Moving SOURCE to the BGCD7000 does not give a tick. I’m confused! I’m waiting for the service kit and will report back if that fixes it.

[TK]

Pretty much every command you execute causes a status update to be sent over datalink, but not all signals are displayed on the Beolabs.  Bass and Treble changes will also send status updates, which are primarily intended to update the MCP.  You can see in this video I made how many signals are sent over datalink reporting system status through regular use:

https://www.youtube.com/watch?v=Nc2g24O34hk

[Dillen]

Replace the small capacitors in the regulator circuits.
3x 10uF and 1x 22uF if I remember correctly.

Martin

[kees.de groot]

Hi Martin, nice to hear from you. I’ve purchased the service kit from DK Sound Parts, I think these caps might be included, where can I find this specific circuit?

Kees

[kees.de groot]

Hello! I’ve replaced all caps on the power supply and pre-amp boards, including the relays and big 10000 uF caps. The tick is still audible for every interaction with Beo4 or MCP 6500. I have resoldered and checked the connections on PCB5 and the wires going to the pre-amp board and relay daughterboard. Tested with two different sets B&O MKIII and a set Bosscom MKII cable, same result (shockingly the fully wired MKII cable did not improve anything). Any help would be appreciated. Could it be my Beolab 9’s contain the fault? NB: Wiring the BL9’s in “series” does not change it either.

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