As I was doing the 3702 boxes, and all the tools was there, I went on with the top cover for the BM 400, first I checked if the aluminum rack was realy anodized and not just painted, tested with acetone, it is anodized, to protect it from getting sanded I covered it with painters tape.

Sanding the side panels I hung the top cover over the table edge, to have support and not to brake anything.

After sanding I cleaned one more time with acatone and applied Old English oil as Rich's wife recommended (As Martin cant post anymore, maybe his wife can stand in for him), Just a little on a piece of good quality Swedish toiletpaper (kittchen roll) and apply, following the wood grain, let soke for a cup of coffee and a cigaret, dry of with a clean rag and apply a second time, let soke and polish of with a clean rag.

Finished, BTW Old English goes a long way, I used it for 2 speaker boxes and this top cover, and the bottle still appears full to top.

Here to show you what a beautiful job the Beo carpenters did in these days, the top and the side panels are made from one same piece of veneer. side view 1

Side view 2

Lovely work Soren, I always think that this is the best part of any project, the time when you give the woodwork a good dose of TLC.  A liberal coating of wax and a good shine seems to enhance the sound as well, making all of that work on the internals worth the effort.  You have here an excellent example of what can be achieved and it looks brilliant.

Regards

Geoff

Coming along nicely!

I was lucky not to have to do anything on my BM 4400 woodwork which is mint!

Most B&O gear damage is due to stocking and stacking, changing uninformed, careless hands, because the original owners would have taken great care of what they had I'm sure!

Fortunately, my newly acquired Beolab Terminal hasn't been in some shoebox with other uninteresting Japanese waiting-for-the-tip remotes!

I have the resistors that I have to change, but yesterday I had all the tools out fixing the boxes for the 3702s, I should have worked on the BM 4000 but I was nervous and afraid to do it, I'm a coward, but today I'll do it.

Søren Mexico:

I was nervous and afraid to do it, I'm a coward, but today I'll do it.

And shoot a video when you first plug it!

Changed the 4 resistors, but no luck, failure is still the same, and the old resitors was OK, only some 2 to 3% difference, was checking right to left channel with and without power, and found some more points with voltage and resistance diff. will continue tomorrow

Søren Mexico:

Today I went after my missing left channel, first I connected my BS 3000 from aux to tape1 in, to check if it was the reciever or the output stages, well, same failure, no left channel, following the drawing I started with the 70 V circuit, same V, L and R, went on crosschecking R to L.

After 1 hour reading drawing, finding the components on the PCB and drinking a lot of coffee I came to the middle of the board, and found this.

Is that a burn mark under the 15nF capacitor on the right?

Menahem

No Menahem, no burnmarks must be the flashlight, and the right channel is OK

The left signal comes through C501 - did you get a good waveform there?

Then I'd cross-check the voltages at TR48 and TR49 with those in the SM.

Menahem

As I dont have an oscilloscope, no waveform. But, TR48/49 has same voltages as in right channel, also TR51 is same as right channel, the problem starts at the 2 68K resistors 548, 549, after 549 I should have 34.5V I only get 12.xV there, I thought the 68Ks was bad and took them out and checked but they are OK, put in new ones anyway, in both channels. I went from there, crooschecking with right channel, with no power, checking components one by one in the left channel, found differences in one resistor and the diodes 563,564.

Thats how far I got yesterday, today I will start with the drawings Sonavor placed in this thread  and after that desolder and check diodes and resistors of board. Until now I found only small differences between the BM, the drawing that came with the unit and the drawing in the manual.

I have been checking for loose wires and broken tracks, and I am doing it again as I go, I checked connections, contacts and wires for the high/low filter, and all seems OK.

What about the 569 trim pot?  That is the left channel trim pot you replaced, right?  Did you double-check it is set to the right value?

-sonavor

The trimpot is set to the same value as the right, but I cant adjust it until I get some feed to it. Still looking, but got tired and as my head is spinning, I decided that watching Broncos and a cuba libre was a much better way to spend the rest of the Sunday

Hi Sören,

As there is about 4.2mA (instead of the nominal 300uA) through R548 and 549 according to the voltages given I'd suspect TR52; this is the only DC path that could draw this current through R551/R553 (unless R550 120k is short or low...). What about the 0.77V on the two diodes D563/D564 resp. base of TR53?

On the other hand, the cuba libre was much better on Sunday I think...

Gunther

Søren, have you tested all the transistors?

Gunther I'm working my way through it, and glad that you are here helping, but I'm into the last jobs I have to finish before christmas and will not get much time for the lovely BM 4000 before January, as I go on vacations 25/12 to 02/01 in Yucatan, sun beach and a lot of cubas with the whole Mexican Family I've got here.

Jacques Still missing to check 4 transistors, but I was hanging me up on the resistors and diodes as I thought, there is the failure.

Please check back in January, and thank you to all of you for the help and interesting threads, wish you a Merry Christmas and Happy New Year, Gunther, Glueckliche Wiehnachten und Frohes Neues Jahr, Jaques, sorry my France isn't what it augt to be, but here in Spanish, Feliz Navidad y un Año Nuevo con Salud y Exitos,

Saludos Soren

Joyeux Noël et bonne année Søren !

Enjoy your Cuba libres and the sun!

Got to it today, the failure I made was reading the drawings when I installed the big transistors, in the drawings the placement is different from the real placement, drawings says left to right, 3001, 2501,3001, 2501. Real is left to right 2501, 3001, 3001, 2501, and thats why the left channel didnt work. Good thing is that I learned a lot from searching and measuring, bad thing is that I have to realize that I'm stupid

After changing the transistors and a pair of resistors that showed diff. values right to left channel, I powered up and there it was, what an amp, way better than my 901 and 2400, now I cant wait to get 3702s connected, waiting for parts.

Here the BM 4000 playing, very good amp even with my 2 way S45s it sounds way better than my BM 2400, I'm Happy

Looks great Søren. 

-Sonavor

Very good!

I'll learn from you, so I don't make that mistake!

Enjoy it - it's a first-class unit.

Menahem

Have been playing now, at volume level 3-5, for about 5 hours, FM, Phono and Cd through tape one, all 6 preset station scales are spot on,  main scale spot on, AFC works, filters works, Loudness works, speaker 2 works.

Cooling elements stays at hand warm level all the same.

To play ambio, is it posible without an ambio record ??