This BL4000 was bought in DK 2002 and until 3 month ago it was working without problems, I found out a fuse was blown, a try to get it from B&O in Mexico city came out negative, they only sells equipment, Sheffield send me 5 fuses for free, thats the forum guys, always helping where posible.

To take apart the BL you will need a philips screwdriver and # 9,10,15 Torx.

The fret comes of by just pulling out in the middle and hook it out to the side, now loosen the 3 philip screws holding the aluminum cover.

Pull of the cover, taking care not to damage the on/off switch, it may come of a little hard the first time, use a flat srewdriver to carefully break it free. Now unscrew all the screws around the front, remember the screw sizes. The middle screw under the alu cover has a cobber lip attached.

The front comes of with the drivers attached, same as the alu cover, may be a little hard the first time, disconnect the 4 cables, the cable connectors has a small lip you will have to press before pulling, no need to mark the cables, just remember, red is woofer and lilac is tweeter.

Now we get to the inside, and can see the PCBs and main transformer. Take a pic or use this one to remember where the foam is placed.

I want to get to the Stand by circiut, the upright smaller PCB is it, to make it easier to check it, I take it out, take of all jack connections, mark them or remember where situated, unscrew 4 screws (torx) from the main transformer, wiggle it out, unscrew 3 screws in the base and the base comes out with the PCB, unscrew 2 srews and the PCB comes of the base.

It now time to consult the manual on site, I know the bad fuse is F4 and have to find out why. Locating F4 in the drawings I find out that it is fusing the primary coil(s) of the On print transformer, as I have a US type BL, I have F3 and F4, 220 V types will only have a F5. The big brown case on the PCB is the transformer T1.

The 2 smal brown pieces to the right of the transformer is F3/4, below in the middle is F1/2, check the drawing in the manual. Checking the fuses, F4 bad and F3 some 8 Ohms resistance the new ones shows some 8 Ohms too. Now I open up the other BL to have something to compare with, I'm a mecanic so electronics is'nt my speciality, but checking and comparing is posible with a multimeter. To get the same conditions on both PCBs I disconnect all jacks and pull out all fuses. First thing is the T1, it has 2 primary coils and checking Ohms over the coils (use drawing to see how)I find one coil with no connection and the other one only some 200 something Ohms, where on the good PCB i have around 600 Ohms on both coils, the secondary coil shows the same on both PCBs. To be sure that the T1 is the only thing bad, I cross check all components on the PCBs, and find no more differences, I also very carefully connect the main power to the BLs and the mains on the PCBs, check the in V and out V on the Main transformer 0T1, around 24 V out on 0T1, depending on incoming V which is pending between 114 and 118 V at the moment. The On print transformer on the good PCB is showing 23.4 to 23.7 V on the secondary coil.

I think I found the failure and the question is now where to get a new On Print transformer T1 with 2 coils 110/220 V in and 23.5 V out on 1 secondary coil.

On the transformer is printed: DT 11353-1, and B/O 8013582 (sparepart number) and REV 01.

Søren Mexico:

On the transformer is printed: DT 11353-1, and B/O 8013582 (sparepart number) and REV 01.

The obvious answer is get the B&O spare part.

It is probably some generic 2x115V / 24V PCB mounted transformer, but to find a 3rd party replacement anywhere you would need to know the power rating and the exact footprint. I'm afraid finding a direct plug-in replacement with a dual primary and single secondary won't be an easy task (I checked my usual sources, no can do in any size).