Thanks for the suggestion. The tweeters looked fine but I switched them round as suggested but it made no difference. Same problem....one speaker fine but the other is red with the standby LED but when sound flows it goes green for a millisecond then cuts back to red. It looks like a safety switch cutting out. My next step unless anybody has a different thought is to release the 10 screws holding the cooling profile and lift it aside to release whatever is underneath which I think will be the main board but unless i find black bits or a blows fuse (some hope) i'm in trouble. It is very hard to give up on this speaker because it is possibly just a small issue.

Nothing to loose by trying to look for a physical fault such as a a disconnected part. If you can find nothing it might be a pan B to open the working one along side and check the voltage through the speakers. 

Looks familiar?

Dear Beobuddy, it doesn't look familiar because I cannot get the aluminium cooling profile off...I removed all the screws and the two screws at the bottom but it won't lift off and i'm reticent to use a screwdriver to help it. All along the dismantling i'm nervous to take a step too far which makes the problem worse. Were you suggesting that when the profile comes off the problem becomes clear? In the meantime i'm trying to have a dialogue with B&O who seem to staff their helpline web with less than helpful people who so far have told me ....the speaker seems not to be working (I know), we can't  help you over e mail (I think that at least B&O engineers could give a view on a fault which I have fully explained and they must have seen before) and go to your nearest service centre (having explained 3 times I live in Malta and there are no service centres). I don't quite know where to go with this and I cannot get my mind round junking two BeoLab 1 (in their day) flagship speakers because I can't get any sense from B&O. Anybody seen this problem before with BeoLab 1's or does everybody just junk B&O equipment when it fails. 

John, do not despair someone on Beoworld has the know how to get past your problem. No more junking talk !

Hi,

You can check this, maybe it some speaker or more that are fail  check info below:

Thanks tompa, that is very helpful and i'll check the connections as suggested.

The amplifier I have here has the symptoms of starting with a green led and after 1-2 seconds back to the red one.

Swapping the amplifier module to another lab 1 doesn't solve the problem.

The problem lies in the amplifer itself.

I have hardly spare time to investigate. I have 2 amplifiers of which one is defective. So I can measuring differences. But then again. What causes the fault/difference if you don't have a diagram on component level? Experiences with measuring faulty components and changing them isn't always the solution. Like for instance replacing blown transistors without proper adjusting idle-currents or offset-voltages.

But the story will continue...(I think and hope (diagram)help is on it's way)

I have checked the individual loudspeakers visually and they all seem ok. I managed to flip over the cooling profile and set it on its back to have a look at the boards/amp to see if anything obvious. Several posts ago I made a tongue in cheek comment that it would be great to find a blown fuse. What I found is that the smaller board (I don't know what this is called but it is the board closest to the bottom of the speaker) there IS a fuse and the glass is black/smoky suggesting that it is blown. The fuse is small 2cm long and thin and although it is difficult to read, even with a magnifying glass, on one end the contact  seems to be stamped VAL250V....cant read the other end. Anybody have an idea what the value of this fuse is or what it protects and where I can get one....is it a special fuse from B&O or a common item. Any advice on this appreciated.

Well now you have localised something visual. It would help if you could photograph the board and damaged part.