Did you locate the source of the smoke?
Was it the IC or an emitter resistor ?

Martin

The IC was hotter than h**, I checked resistors on board, will desolder and check again

IC 200 emetter resistor unsoldered and checked OK, the other 3 on board same resistance around 0.5 Ohm

Fault finding in a complementary output stage like this can be a headache;
You find a bad component and replace it. Power up and it still doesn't work.
You find another bad component and replace it. Power up again and it still doesn't work.
- Because the second bad component caused the first one to go bad.
- And it has of course gone again now.
You then replace both at the same time - but it still doesn't work, because the first one caused a third component later in the
circuit to go bad and you haven't found that one yet.
What you don't know and won't find is that a fourth component suffered from a severe overload due to the failure of the first and
second components providing it with internal scars that won't show until you least expect it. By then it will take all the others down with it plus
a few more and you will never see the end of it.

There's really only one safe way to repair an amplifier like this and that is to replace pretty much everything from
the differential amplifier outwards.
Check (or even better) replace TR212, TR213, TR214... onwards, as well as the trimmer, the two diodes and the emitter resistors.

Martin

Hi Soren,

I haven't checked the part numbers but spotted these the other day:

Last time I troubleshoot a 2400, It took me weeks to found out that the only cause of my problem was a simple open resistor in the output stage. I measured all resistor on board and compared their values with the opposite and working side, making a chart. Not to forget these broken copper traces that gave us all headaches one time or another...

When you'll find the solution to your problem (you will) it'll probably become one of your favorite pieces. Just because of the gratification of the fault finding.

I'd love to have a 1900, with the old square type light display. I must admit, however, that I prefer the look of the 2400. But the 1900 is THE historic piece that shaped how B&O would look for many years after.

Guillaume

I hate this, I will now have to pack up the BM 1900 set it aside and wait for parts, but as luck will Mouser has a better service down here in Mexico now. PIB. I will give it one more shot today before packing up. I have to order caps for the Beocord 2000 anyway.

I have Steren down here on the corner but its very limited what they can offer, and most of it China made. I have to go looking for the transistors, and then maybe at the same time make an inventory of my electronic parts, they are in 3 different places, well sorted in old and new.

Found enough Transistors for left channel, also diodes are there, started changing transistors from TR210 onward, slow going, changed 6 just now. Non showed bad measured off board. Tomorrow onto the rest and then resistors, slowly this thing starts to nerve me, if this doesnt work it will get the same treatment as the BM 4400

I changed nearly all TRs and diodes in the left channel, as I think something is wrong in the 15V supply and/or the fault switch I went there too, but ran out of TRs, went on checking resistors, and found this on the way

Thats in the right cannel, not in the left where the IC 200 was bad. Tomorrow more

Hi Soren , I have the same problem with my 1900 , I am cahnging every TRansistor and diode and checking resistors on the left power channel . 

I will check it today if it is working .. 

one thing is that I did not found porientiometer that is in the last stage of the power amplifier , could you send some links ? 

Also fir all the lamps that still working but I will change it anyway .

thank you very much