BL8000 starts in green and hum

7 replies
PI
Offline
Pindsen
Bronze
Posted July 12, 2022 at 09:13 GMT
#1641049
I am looking at an Beolab 8000 which puzzle me.

There are no audio cable connected, when AC power is turned on it starts with green LED and hum - I would expect red LED and no hum.
There are GND connection from audio connector to PCB2 connector P4-3.
Apprently is picks up noise internally, but where from?
Any idea what that could be?

/Pindsen

Location: Denmark

KolfMAKER
Offline
KolfMAKER
Bronze
Posted July 13, 2022 at 07:55 GMT
#1647783
Did you connect a Powerlink or RCA cable to one of the connectors?

what do you see and hear when you do that?

Location: The Netherlands

My B&O Icons:

Beoremote-Beo4.png Beoremote-Beo4.png
Beovox.png Beovox.png
Beosound.png Beosound.png
Beosound-9000.png Beosound-9000.png
Beolab-18.png Beolab-18.png
PI
Offline
Pindsen
Bronze
Posted July 13, 2022 at 17:40 GMT
#1647790
No I tried without any audio cable because that to me should be a good starting point where I would expect red LED and total silence.

If I apply a powerlink cable it is more or less the same with green LED and around same hum, but if I apply an RCA cable the hum gets a lot higher.

Location: Denmark

PI
Offline
Pindsen
Bronze
Posted July 14, 2022 at 20:05 GMT
#1647803
I have discovered that if the outer aluminium part is being touched it increases the hum. My assumption is that the aluminium part is/or should be "grounded" to the amplifier via the six screws?

Another discovery is that when doing a short circuit of the RCA input the noise in the RCA switch selection lowers to nearly nothing.

I have tried to see if the internal cabling is correct, and it seems like. It though wonders me why the audio cable runs directly under the transformer.

Location: Denmark

PI
Offline
Pindsen
Bronze
Posted July 15, 2022 at 20:44 GMT
#1647820
Okay, to finish up my own thread :-) my conclusion is now that there did not exist a proper connection between aluminium part and amplifier despite being screwed together. I noticed that the screws are some kind of black CED coated, and by working the screws back and forth several times the hum disappeared and the speaker now works as it should.

Location: Denmark

SP
Offline
sprockett
Bronze
Posted January 25, 2023 at 11:23 GMT
#1653181
I noticed the same behaviour with BL6000.

Basically, when you are in LINE IN mode,  you NEED to have everything terminated properly, even if there is no RCA plugged in.

For my case, by BL6000 needs to be have Line-in RCA plugged in to the source using a cable, before everything is silent. If you don't want to plug anything in, you need to short the input via a terminating plug.
DI
Offline
dinyavin
Bronze
Posted April 19, 2025 at 01:31 GMT
#1669545
dear
link
Okay, to finish up my own thread :-) my conclusion is now that there did not exist a proper connection between aluminium part and amplifier despite being screwed together. I noticed that the screws are some kind of black CED coated, and by working the screws back and forth several times the hum disappeared and the speaker now works as it should.
it seems that I have the same issue. Did you mean bolts which are connecting aluminum heatsink (black one) to the main box" or bolts which are connected amp itself to the aluminium heatsink?
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