Your phone is isolated to Ground and to the 240V power.

RCA from somewhat else as a sound source is not isolated, it can have voltage to Ground. Sometimes very high voltages... i found already antennas with 190V (!!!)

Measure before plugging in the RCA the voltage between source and 8000. Measure ground to ground and signal to signal. There will be some voltage. Use DC and AC (!!!)

Use 1 (!!!)  multi power plug/cord for source and 8000. Then the voltage should be gone.

If gone, your house installation has a problem.

 

Thanks a lot Die_Bogener ! I now also noticed following. I touched the solder connection of the Left/Right signal wire (see red circle), with a screw driver. And immediately, the power switches ON. And when it is on, the hum/buzz gets stronger. Same happens (obviously) when I touch the back of the RCA connector (as it is the same connection of course). This does not happen when I touch the GND connection. Login to view image Concerning your advise to test by measuring (before plugging in the RCA):

• The voltage between source and 8000, both AC and DC
• Measure ground to ground
• And signal to signal

Just to be sure, do you mean …

• Ground & Signal at the RCA connector on PCB 05, at one side?
• And Ground & Signal at the P4 connector Amp PCB, as the other side?

 

Measure the sound source device to the beolab input. Without the RCA cabel connected.

Some houses use different power installations... and have problems with the 220V power distribution. Sometimes there are some hundred Volts between the power plugs.

Soooo, use ONE power plug for all of the hardware you use. Connect Beomaster, Beolab, all sources and loudspeaker with ONE power plug in the wall. And disconnect the antenna...

 

I had a BC9300 here with 190V Antenna to ground ...making a spark when plugged in ! And when touched making a gribbling hand...

Thnx Die_Bogener!

The issue of Auto stand-by clicking On-Off-On all the time, even happens when having no audio source connected to PL or RCA/Line in.

What about that ?

New checks & tests

I have just swapped the PCB01 TRAFO board from a working BeoLab 8000, into the troubling unit. I kept the other unit the same (PCB02 Power Supply & Amplifier board).

Result: no issues with Auto stand-by, just smoothly switching from ON to OFF/Stand-by when it should. Also no noise/buzz.

So something must be wrong on PCB01 the Trafo board.

Check the standby trafo. 2x 18V~

I have now been able to do some measurements on PCB 01. I did the same on another PCB 01 from a different well functioning BeoLab 8000, and put them side by side. It looks like this: On the left side of the blue dotted line, the well functioning BeoLab 8000:

• Left/red = measurements in stand-by/Off mode.
• Right/green = measurements in On mode.

On the right side of the blue dotted line, the BeoLab 8000 with issues:

• Left/red = measurements in stand-by/Off mode.
• Right/green = measurements in On mode.

 

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Login to view image

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So compared, what I see:

• T2 shows 20 and 23 V, so not even.
• Else, I see no differences.

  Question Is there anything that we can conclude from this, that helps towards a solution?

The voltage/load of the 2x18V is not quite symmetric, the load is unsymmetric... around ~20V is ok.

The problem does not move with exchanging the power boards?

If no movement, the problem is not the power supply...

Probably the amplifier itself... broken line, defect cap... check the +/- 15V supply. The on/off logic is on the amplifier...

Thanks @ Die_Bogener, for your recommendations. What I did next: I swapped the PCB01 TRAFO board from a working BeoLab 8000, into the troubling unit. I kept the other unit the same (PCB02 Power Supply & Amplifier board).   Result:

• No issues with Auto stand-by, just smoothly switching from ON to OFF/Stand-by when it should.
• When the BeoLab with this (swapped) Trafo board is on, there is also no noise/buzz.
• When I touch the 5-pin cable when the BeoLab is ON, there is some noise/buzz.
• When I touch the 5-pin cable when the BeoLab is OFF, it does not cause the BeoLab to switch to ON.

  Conclusion: The amplifier seems to be fine. But the Trafo board/PCB 01 must be having the problem.   Question: Since the voltage measurement (see earlier post) on the T2 trafo shows a non-symmetric load (20 Volt vs 23 Volt):

• Is the T2 trafo the problem source, or could it still be some other part or component on PCB01?
• If T2 has to be replaced, what is a good source to find a (reliable & affordable) replacement?

Hello,

Thanks to KolfMAKER for the excellent posts. I am having similar issue on my Beolab 8000 MK2 SN 19.

 

My Problem:

speaker set to Line in / RCA. Only power lead connected.
Speaker powers on, green light then turns to standby momentarily then immediately back to power on, this just sequence keeps repeating.
No issues when connecting with Powerlink.
I have X2 speakers and when checking the other “good one” it just stayed in standby with only power line connected, however when messing with it some more. I got it match the same fault as the other bad speaker, with it jumping out of standby a few times, before it settled into standby mode.

This seems to be a sensitivity issue related to the signal sensing circuit. It appears one of my speakers is too sensitive and the other is on the limit.

I have tied powering off all other electrical systems in the house / testing speakers in same location and I get same issue replicated on the one speaker.

 

From your previous post:

“Since the voltage measurement (see earlier post) on the T2 trafo shows a non-symmetric load (20 Volt vs 23 Volt):

· Is the T2 trafo the problem source, or could it still be some other part or component on PCB01?

· If T2 has to be replaced, what is a good source to find a (reliable & affordable) replacement?

This small inbalance in transformer output may be pushing you speaker over the sensitivity limit?, as earlier poster said this transformer output difference should be ok / within limits.

 

When reviewing previous posts on this issue

Keith Saunders posted about a modification needed to Beosound 6000 with this issue. I will D/M him and ask if he has any input.

/forum/general-discussion-and-questions/beolab-6000-auto-power-on-and-off-problem#post-1807695

Power-link mode: Mount a 1 nF capacitor across 03D1.
Line mode: Mount a diode 1N4148 between 03R126 and 03D19.

Apparently, B&O designed a fix?

Also has any one got MK2 Beosund 8000 diagrams / updated service manual, im not sure if this on the site as im not a silver gold member any more.

In addition, I have reviewed the wiring for line input sensing circuit that seems to be causing the issue and possible problem components however I’m not too sure. Find attached

Best Regards,

Luke