Beolab 4000 Mk2

4 replies
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Offline
perriama (archived2)
Bronze
Posted February 1, 2022 at 09:49 GMT
#2163426

Hi Beoworlder's,

Recently purchased a pair of Beolab4000's Mk2, with the full knowledge that one of them was defective (flashing red light with clicking noise when activated by Powerlink).

Have replaced the amplification boards on both speakers with brand new PCB's (PCB01) and this improved the one working speaker, but although the malfunctioning speaker now correctly powers up and down from Powerlink activation, no sound comes from the unit.

Have tested the speaker array panel (6ohms for woofer/tweeter) and that's all fine. Have replaced some rather suspicious looking capacitors on the main board (PCB03) to. I'm also using a brand new mk3 cables to both speakers.

One interesting thing I found was that when I include the defective speaker into the Beosystem3 configuration and use AST, the whole sound configuration is thrown off i.e. sound channelling is no longer adhered to, with the system playing all sound from all channels to all speakers . Which would possibly lead me to the Main PCB (PCB03) and perhaps to the EQ process in the bad speaker?

I'm at a loss, so if anyone has got any ideas as to what may be causing the lack of sound , would greatly appreciate any advise?

 

Thanks

 

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Offline
perriama (archived2)
Bronze
Posted February 9, 2022 at 08:22 GMT
#2163427

Narrowed this problem down, and it is indeed an issue with PCB03. Noticed on visual inspection that one of the three pin SOT's had blown. Tested with a multi-meter and nothing. Would normally replace the entire board, but B&O do not make or stock this any longer (8003562)?

The blown SOT has the following markings on top 'W6K 80'  (or at least I think with my tired eyes!)

Looking through the extensive manuals on this site, I can only find the circuit schematics for the MK1's. Does anyone have them for the MK2's?

Thanks again 

 

Beobuddy
Offline
Beobuddy
BronzeFounder
Posted February 9, 2022 at 08:43 GMT
#2163428

If that one is blown, you might wonder what else more has been damaged behind that one.
Diagrams on component level were never released and lay probably lay somewhere in some kind of vault.

Until recent DK repaired these boards themselves. Not sure whether they do and are capable of doing (because of the large amount of shortage of components worldwide).

Location: Utrecht

Quite a challenge to achieve "Less is More" while having the Beovirus.
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Offline
perriama (archived2)
Bronze
Posted February 9, 2022 at 10:18 GMT
#2163429

Indeed and thanks Beobuddy. I have replaced or mended all but this board and was hoping to rescue it, but guess it's not possible.

There was obviously some kind of catastrophic power surge on the unit, with evidence of burn from the amplification board on the insulation foam.

So if anyone out there has a spare main board (PCB03 - 8003562) gathering dust, please don't be backwards in coming forwards.

 

Thanks

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