Hi, I have the primary loudspeaker sockets muted in my BM5500.

All was OK untill I plugged in headphones. They worked fine, but after unplugging them, the speakers did not come up anymore. Changing to the other sockets help, so the amp is OK. Pressing the mute-button does not release it, nor do repluggin/unplugging the headphones.

So, should I go after the headphone plug or the mute relay or its circuitry to find the problem? 

I think I've seen a discussion about something similar, but could not find the thread.

Thanks, 

Pekka

Do you hear anything happening with the relay when you try to mute/unmute the sound? (use the remote to avoid the front panel click from masking the sound)

If not, I believe the switch in the headphone socket is somehow stuck/shorted and the Beomaster now thinks there's a plug inserted all the time. If you haven't owned the Beomaster since new, you might even find a piece of a broken plug in there.

The relays themselves have a habit of not making good contact as well when they age, but it would be suprising if that happened when you first tried the headphones, with no prior problems.