Beolab 4000 type 6637

[yonderdode]

Does anyone have a circuit diagram schematic for these odd looking POWERED B&O speakers?

http://www.tmraudio.com/product/undefined-554

The problem with the design is that the foam material inside decays with age and becomes sticky and conducts on the main pcb causing death for certain parts. One of mine is stuck in standby (red led) because it "thinks" it is getting an overheating signal and causes the power supply relay not to be activated. Manually operating the relay proves the amp works in all other respects.

CCT diagram very welcome!

Thanks, YD.

[tri-comp]

I have this service-manual.
PM me with your e-mail address for a copy.
Good luck with repairs.

[yonderdode]

Hope you get the PM with my email address.
It is so long since I used this wonderful site, I could be rusty so hope it is delivered.
Delighted to get your assistance.
YD

[tri-comp]

Sure, no problem; the manual just went out to you.
Good luck with repairing the SMD-circuit

[yonderdode]

Success & Hallelujah!
A 100 Ohm SM resistor R139 had gone high in value to about 700 Ohm right near the small 4-way ribbon connector from the power supply - just exactly where the spongy sticky foam had decayed on the board.
Having replaced that before, it did not spring back into life and I really needed the circuit diagram to do voltage checks in the area of R96, R122, R123 and eventually found some open circuit print in two separate locations just below the black plastic cover that hides the din connectors and the rear panel selector switch.

Thank-you very much for your help.

[Nickthedentist]

Well done!

Originally Posted by yonderdode

...just exactly where the spongy sticky foam had decayed on the board.

This seems a common problem with B&O speakers.

My parents' Beolab 8000 active speakers wouldn't switch on, with the LED showing red irrespective of the switch setting and presence of a signal. I found that one of the traces on the PCB (no SMD in that region, thank goodness) which led to the relay coil, had been eaten through and had gone O/C.

A bit of a messy job to do, but well worth it. Except that within a few months, burglars made off with them A credit to B&O though - how many theives would usually bother stealing 25 year-old hifi gear? And the insurance decided to pay out £2000 for them, which amazed us all. We spent £10 on a pair of less attractive Wharfedales from the local charity shop and banked the rest for a rainy day.