Reply To: BeoLab 8000: 5-pin cable from RCA-PCB to LED-PCB sensitive

#10187
KolfMAKER
BRONZE Member
  • The Netherlands
  • Topics Started 14
  • Total Posts 104

@Die_Bogener: As you suggedted, I connected a shorted RCA plug to the RCA connector on PCB05. Result: the hum is gone, Auto stand-by switches to OFF and stays OFF, and when touching the P4 cable, Auto stand-by does not switch on.

So this does look good! But now I need to make a next step, because I need the RCA connections, so I cannot keep them shorted.

 

Here’s some additional things I changed, tested and the results.

 

Checks 2

I took another look at PCB05: used a dentist tool to scratch along the edges of the RCA GND contact on the PCB, and at some other connections/traces on the PCB. Just to be sure, there’s no traces that make unwanted contact.

Tested after checks 2

  1. Input switch set to RCA: When the BeoLab was switched on again, the hum was more or less gone. The Auto stand-by does switch to OFF, but after one second immediately switches ON again, and then repeatedly goes ON – OFF – ON – OFF.
  2. Input switch set to PL: Auto stand-by switches OFF, and stays OFF > OK. Touching the PCB, P3 / 4 cables, etc. has no influence on Auto stand-by, it stays OFF > OK.

 

Checks 3

Extra checks on the GND and disturbances of the RCA plug on PCB05.

 

Tests with Checks 3

All checks done with the input selector set to RCA.

  1. Connected a wire between GND of the RCA connector outside shell above the PCB, and the GND underneath the PCB. Problem remains > No positive result.
  2. Put a metal cap over the RCA plug for shielding. Problem remains >  No positive result.
  3. Connected my old iPhone with a ‘mini-jack-to-RCA’ cable to the RCA socket on PCB05 > No hum, Auto stand-by switches to OFF and stays OFF.
  4. In situation 3. I also touched the cable of P4 on PCB05. When touching it, Auto stand-by switches to ON. When releasing the P4 cable, Auto stand-by switches OFF again and remains OFF.

 

What bothers me is, that the Auto stand-by actually works well, but …

Touching the P4 cable makes the Auto stand-by switch ON again. Therefor, it is not yet working reliably.

 

Questions

  • What do you conclude from this?
  • What next step do you suggest?

 

 

  • This reply was modified 3 weeks, 5 days ago by KolfMAKER.