Peter,

Is the picture you provided of a 240V version?

Thank you,

Rob 

Probably the BM is still intact. The owner before had modified the power supply in the wrong way... the two coils worked against each other, the direction of one coil is wrong.

This inducts a high current in the coils and blows the fuse at once, but no current goes to the secondary part. Plus and minus is zero ...

So, if you change it exactly like Peter's foto, then it should work again

By any chance, do you have a photo of a 110V model?

Looking at the wiring diagram, the wires on the input side "appear" to be correct (for a 110 model).  However, it looks like someone attempted "clean" the signal from one of the output terminals by running a cap to ground in series with a resistor (all of which I plan to remove).

-R 

There are two resistors (one each)  running from the negative terminal to the chassis.  There is a single capacitor between one of the positive outputs to the adjacent negative output.

 According to the stripes the resistors are both:

65300 (Ohm) with +/- 2% tolerence

In the picture I submitted earlier, you can see one resistor in series with the cap leaving the negative output (close up attached).  The other resistor is similarly installed on the other negative terminal (no capacitor there), but difficult to see in the picture. 

Not sure where you saw the second capacitor :) 

Is there a replacement power supply existing? Is the original still available as parts?

My BM has the usual humming feature relating to power supply aging.

Hi:

Let me jump in here re: power supply hum because I have had experience with this on my BC 9500

This may have nothing to do with power supply aging.

1) It may be dirty AC current in your house wiring! Try taking this to your neighbour's home or to work. Somewhere far away from your residence to see if it goes away.

I had a very noisy hum on my 9500 and I even posted to this forum asking for a spare transformer. It turns out when I relocated, the hum went away!

2) The transformer sits on rubber grommets (or sleeves). These serve as shock absorbers isolating the vibrations caused by the AC induction in the core from resonating in the chassis. It is possible that they have dried out or that the screws holding the transformer is either too loose or tight.

3) Finally also check voltages in output of the power supply, the filter capacitors and bridge rectifier for normal operation. Compromised components could introduce high loading on transformer causing it to hum.

B&O used really nice transformers! Unless it has had bad case of over heating, they last!

Check first before investing in new transformer :)

Derek 

After a little probing, it appears that the rectifier (D3 on the circuit diagram) is bad.  According to the service manual, the part number is BA423.

 I am having a bit of trouble locating the part.  Does anyone have a suggestion? 

I was looking at the wrong parts list :).  The correct part number is B80 C3700/2200

I replaced the rectifier.  The fuse still blows as soon as power is supplied.  I unplugged P14 and P15 to isolate this part of the circuit - and still the fuse blows.  Now I just need to find out what is shorting to ground....