Hi Jeremy

Last week, I encountered a similar problem on a BM5500 which had been given to me and I managed to get that one to work properly.  I have just found this thread and can easily relate to all of the points that have been raised.  Yes, I did put my speakers into the top sockets thinking that they were speaker 1 and consequently wondered why the speaker 2 output from the bottom sockets would not work.  This is a very easy mistake to make on these machines.  After that was resolved, my logic for solving the problem was as follows:

Connect speakers to the speaker 2 upper sockets, both channels work properly – no problem at all with the signal path to speaker 2.

No output from the lower sockets speaker 1, suspected that the relay was damaged or was being grounded via the headphone socket. 

Mute signal from the MCP5500 did result in a clicking relay but no change in speaker 1 output.

Headphones worked properly on both channels, confirms that the signal path was OK.

No change to speaker 1 output when the headphone jack plug was repeatedly put in and out – will now have to open up the machine to examine the relay.

Took off the lid and raised the top PCB into the service position – rechecked that the speakers behaved the same as before and they did.  Can now see that the relay is working when the mute signal is being applied and the relay is not activated when the power is first switched on.

Decided to remove the lower PCB to test the relay.  Found that there was a very high resistance across both contacts when the solenoid was off.  Contacts must be oxidized.

Removed relay and swapped with a similar one with good contacts – everything on speaker 1 works properly now.

As a follow up exercise, I tried to repair the relay but battled to get the clear plastic cover off without smashing it into one hundred pieces.  I have now cut the cover off using a fine saw and Dremel.  The terminals can be cleaned and the resistance is now back to normal showing a good connection.  If I ever need to use this relay again, I have the option of gluing the cover back in place or holding it in place with plastic sticky tape.  I think that I will choose the latter option as that will allow me to service this relay while it is on the PCB.  The odds are that those terminals will oxidize again fairly quickly.

Hope that this has been of some help.

Regards

Geoff

Hey everyone,

I wanted to let all of you who helped me out with this know, that I have sold the beomaster 5500 that did not work, I got more for it than what I paid for the 2 5500s and 6500 together so I dont mind it being gone.

I have kept the 6500 and am currently repairing it. Geoff I want to thank you for your detailed post. My beomaster 6500 is also showing the same corrosion on the relay, I will go ahead and do as you did with your old relay and get that cleaned up.

You are all a bunch of great people, very friendly and willing to help, I appreciate that a lot.

Thanks again!

Jeremy

Keep in mind that cleaning the relay may not be a long time fix. The contact points have a thin plating (platinum?) and when it's gone, it's gone and the points will oxidize again practically while you wait. Never use anything abrasive on them, regular piece of paper dipped in isopropanol, pulled back & forth between the contacts, will be enough to do what can still be done.

Of all the B&O kit I've acquired, I've had a few with apparent muting relay problems, but I have never actually attended to any of them - they have all sorted themselves by simply giving them some use. Often the receivers sit unused for a longer time before people finally decide to get rid of them, and the points oxidize even if they aren't worn yet.