Beolab 4000 switching itself on

[Ray Dahr]

Hi everybody, I’m a new member here with a Beo problem. I have a pair of Beolab 4000 MK1 active speakers. One of them has started to constantly switch itself on from standby and hum, without an audio input signal. It does this with or without the audio cable plugged in, with different power cords and power outlets. Any suggestions what may be the cause?

Thanks for any clues.

[kirin]

Hello, my experience was unfortunately, that this is a beginning of the end of a a beolab 4000 speaker due to the foam-rot issue, just search the archive forums for „Beolab 4000“ and „foam“. These damping materials inside the Beolab 4000s are getting old and sticky and etch the PCBs to death. Resulting in the case that Beo4000’s do not switch on any more.

BTW, did anybody manage to repair them?

Best regards

[Ray Dahr]

Thank you for your reply. My speaker has the white foam, there is no visible deterioration of foam or boards.

There is no problem switching it on. Quite the opposite, the problem is that it constantly switches itself on while in standby, with or without an audio signal, with or without an audio cable plugged in. It makes an annoying hum after it switches itself on.

[spassmaker]

Hi

As you wrote that there is a white foam inside , it might be that teh foam was already renewed from a preownwer.

Could be that the old foam was not removed completely from the PCB’s and now the rest of the old foam did his work.

Inspect the PCB for unusual colours of the traces and parts.

Kind regards

Christian

[Die_Bogener]

Clean the manual switch, it’s oxide and old grease … L … R … Auto

Use the switch, many, many times…

[Ray Dahr]

Thanks for the suggestions.

The boards in these speakers look as new, no discoloration, no deterioration.

By swapping boards with my good speaker I have determined that the problem is not with the board that has the switch on it.

[Author]

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