Hi Krais

Was the Beomaster already serviced?

If so often the AC Line capacitator on the relay board is forgotten, could cause a short, had myself one defect while the amp was playing music, a lot of bad smelling smoke and crackling like a firework, but the amp was still playing music.

So this cap goes often into heaven and could cause a short that could engage your house breaker circurit.

The fuses of the Beomster come later in the circurit diagram as far as I remember.

IF YOU ARE NOT FAMILAR WITH ELECTRONICS  AND HIGH VOLTAGES ASK A 

                         FRIEND OR  SOMEONE WHO KNOWS ABOUT !!!

                                               DANGER 220 VOLT!!!

                                PULL OUT THE MAINS AC PLUG FIRST!!!!

I write this because I don´t want to be responsable when you or someone else gets hurt or your house is burning down.

Turn the amp with it´s back to you and losen the 4 screws of the lid in the middle to get access to the relay board.

Have a closer look to the yellowish square capacitaor... is it broken or exploded?

Let us know what you find.

This must not be the cause of this behaviour but that´s the way I would go first, maybe others would go in another direction ....

Kind regards

Christian

Hi Christian

Thanks for the warning, yes I'm aware of the dangers of high voltage.

I already had replaced the AC line capacitor with a new X2 safety cap when repairing the BM8000 a while back. I double checked and it measures fine, no short (and btw the safety cap is located behind fuse F2 which hasn't blown).

While investigating PC7 I also measured resistance on the primary windings of the two transformers: 1.25 ohm for the large transformer and 56 ohm for the small one. I believe that is consistent with expected value ranges. 

Also, the fuse on the power supply board PC6 is fine as well.

Hi Krais

You are right, the fuses are before the cap, and as the fuses are not blown... it´s very strange that the house circurit breaker has engaged.

Would be nice to have a variable isolating transformator with an amperemeter, so you could see what´s goind on while you crank up the voltage.

You could ceck the rectifieres and the large caps (10000uF) of the main rail voltage + - 55 Volt .

You could pull off the main +- 55 V voltage from both poweramps ( isolate the plugs ! )

I won´t give you more hints to sort out the trouble, because I don´t know how far your skills in ekectronic is and I don´t want that you burn your fingers or even more.

We are talking about an 220 V house circurit breaker, that´s the time for me to stop, hope you understand me right.

So maybe there is someone else who gives you some tips.

Regards

Christian