Hagen,

Your feedback is most interesting, but as you have said it raises as many questions as it does provide answers. In my view if the problem is caused by RF interference, then it is going to be in the range 400-500 Khz. I would also start focusing on the mains except for one point and that when you used your home-made Faraday cage, your LC2 worked. Assuming you can reproduce this working situation every time and it was not just luck, then it still sounds like RF interference being the most likely cause. If this is the case, then it maybe RF interference transmitted via the mains wiring which is unlikely to be picked up by your measuring equipment.

To prove this point you may wish to install an in-line RF suppressor in the power feed to the LC2 which are very cheap to buy and some examples are HERE

Hi Keith,

yes, it´s a pity that the measurement devices didn´t cover frequencies in the range of the B&O IR system. A wide range of frequencies was not covered by them. Furthermore they did not allow to determine specific frequencies as e.g. a spectrum analyser could provide. 

Do you have any hints, which devices might produce electrical noise in the frequency range of 400 - 500KHz? It must be some equipment that is in use around the clock.

Hagen,

RF interference is actually very difficult to track down because it can be caused by so many everyday products and is transmitted in one of two ways:-

• Via the air as in normal radio & TV transmisions
• Via a electrical conductor which is not connected to earth such as mains wiring.

Given, my previous statement about the outcome of your tests with your home made Faraday cage, it seems most likely that the RF interference is via the air particularly as your building is made of brick and wood meaning it is not really a barrier to the RF signals from outside your apartment. Having said that and using my "Kepner Tregoe" analytic trouble shooting principles it is always good to be able to say what is NOT causing the problem and therefore it would be helpful to prove that the mains transmission of RF interference within your apartment is NOT the cause.

With the above in mind, I would switch off all power to everything in your apartment except your LC2 and wherever possible switch everything off at the main breakers. If the RF interference is being generated and transmitted from within your apartment then your LC2 should start working. If the LC2 is still not working, then the RF interference is almost certainly transmitted through the air and from outside your apartment.

The most common items which can cause unwanted RF interference in the home at the frequency range we are talking about include:-

• Microwave ovens particularly if not correctly earthed
• Fridges
• Anything with a constant running motor
• Low voltage lights driven by an oscillating (i.e. no transformer) power supply
• Products left in "Standby" with an oscillating power supply (most such devices)

For me the best next step is switch off all power in your apartment except to the LC2

 

Hi Keith,

I turned off all equipment in my appartment but with no success.

Then I started examining the mains. I took my oscilloscope and checked my power outlets - nothing but a 50 Hz sine (or so) wave with some spikes that are obviously produced by other dimmers.
However I noticed that there seems to be "something in the air". I constructed a simple antenna consisting of a wire fixed on a slat. I added a simple high-pass filter to reduce the reception of the 50 Hz noise. The filter was designed of a series capacitor of 22 nF and a load resistor of 330 kOhm (f = 22 Hz). The next pictures show what I detected yesterday...

This picture shows the signal I detected. Please note that the peak amplitude is more the 2 Volts! The signal is interrupted every 1/100 second.

It seems to be synchronous with the 50 Hz mains frequency which is prooved by this picture (channel 2 of the scope is connected to the mains - the sharp sine wave added here).

Any idea which kind of electronic stuff is producing such a signal? May be something like a PowerLineCommunication or a babyphone?

As the signal appeared to be quite strong, I connected the "antenna" to my headphone and the other terminal of the headphone to protective earth. A very slight hum could be heard although this headphone has a low impedance.

Tonite the signal is absent and guess - the LC2´s are working!

The next step will be to ask my neighbours what kind of electronic equipment they are using or rather not using this night.

Hagen,

This is fantastic detective work you have done, you now know what the noise type which is killing your LC2.

It certainly does look as if the problem is with one of your neighbours.

One easy way to get acceptance from your neighbours that they may be causing your problem, is to get each one in turn to switch their mains power off and go from there.

Hagen,

Looking further at your oscilloscope pictures gives me the feeling that what we are seeing is an un-surpressed motor or a faulty motor. The type of motor I am think of is a carbon brush motor which has no or faulty suppression. Also, given that it apparently stops at night means that it is either on a timer to switch it off or the user manually switches it off at night.

The key item which is normally switched off at night and uses a motor is the central heating, depending on the type of heating used, it could be a water pump, blower motor in the boiler etc.

I don't know how many near neighbours you have, but as I said before, switching off the power at each neighbour would narrow the cause down quite quickly.

Hi Keith,

I don´t believe that the noise is caused by a motor. The photographs I took from the oscilloscope´s screen are not very clear due to multiple exposure (too long shutter time) and the signal is not totally stable. The real signal clearly shows some sharply formed bursts of data transmission (IMO) following the zero crossing of the mains. However I will keep your hint in mind as I am predisposed because I´m working in the IT business...

Hi Keith,

I just wanted to let you know what has happened in the mean time:

I wrote a very friendly letter to some of my direct neighbours describing the problem and asking them to check their equipment like motors, babyphones and other electronic stuff. I wrote this letter on a day the interfering signal was absent (March, 29) and it didn´t re-appear since that day. So actually I can´t say what is or was the reason for the electronic noise - which is a little pity. On the other hand my LC2s and my Ouverture are working perfectly again since that time and in case the problems return I´m well prepared with measurement equipment to detect the "enemy"!

Until that day - which will hopefully never come - let´s close this topic. Thank you very much for your interest and your help!

Hagen,

As you say, you are well prepared if the problem comes back, but at least your LC2 and Ouverture are now working correctly.

It may well be that one of your neighbours knew they were causing a problem and your letter made them do something about it.

Yes, I agree. May be one of them has a guilty conscience.

Do you know, how the LC2 can be reset to its factory defaults? I would like to restore the original light levels (LIGHT 1 = 10%, LIGHT 2 = 20% and so on) and reset its individual number. There must be a way to do this but nothing is mentioned in the manual. I asked this question some time ago in a separate topic but with no result...
 

Hagen,

I can find nothing whatsoever about returning the LC2 to factory settings. Given that these settings are stored in an Eprom, it may well have been setup outside of the unit prior to assembly.