But, does the resistance vary when turning? On the middle leg that is.

Does R200 affect the offset voltage? Are the correct voltages on the output stages present?

Thanks everyone for the input, it is much appreciated!

Beobuddy, I guess you mean the resistance on R226? That does vary, when looking from the front of the amp, I measure the same value between the right 2 posts as between the left and lower right, this value varies between about 2 and 118 ohms. The resistance between the left and upper right post is nearly zero, about .3 ohms, independent of it's setting. I presume this has something to do with how the thing is wired on the PCB.

Just for comparison I also checked the donor beomaster I got, it has pretty much the same behaviour.

Just out of curiosity, I also checked out the old pots from my own beomaster for both left and right channels. The left channel (which did not blow up) showed about the same values. The right channel pot has very large resistance between A and B, about 1.8k. It's behaviour is very erratic, so maybe this thing caused the initial problem.

I did not change R200 on either the left or right channel, since the readings on the terminals are in spec...

Where should I check the output stage voltages you are referring to?

On the board the midldle leg is shortcircuited with one of the outer ones.

But the between these 2 and the other outer leg, the resistance has to vary. As you already mentioned.

It needs more measuring, thats obvious.

Probably also mentioned earlier, what voltage do you measure across the (emittor) resistors in the outputstage?

There has to be measured an idle current. A zero or to low current results in distortion. Anyway imho anyone aming to achieve a lower idle current than given, doesn't understand the meaning of it.

But that's another story. 

Beobuddy wrote:

Probably also mentioned earlier, what voltage do you measure across the (emittor) resistors in the outputstage?

The emittor resistors are R236/R237, right? The problem is the voltage measured across TP200/201 is 0, these test points are across R236 and R237, so I can't measure any voltage at all, that's the entire problem.

I'm at loss as to where to start looking for potential problems.

Am I risking blowing up the amp again if I put it to use? We're throwing a little party by the 31st and I really need to get it going before then.

Where are you located in Holland. Utrecht an option for you?

Sure, I'll send you a PM so we can get in touch.

Thanks!

Hi BM4, hope you had a good Christmas. Regarding the fault with the amplifier, have you tried taking DC measurements with respect to ground? Also have you double checked your work? It is so easy to make a mistake that is not at all obvious until you go over everything with a fine comb, and then sometimes for a second time!!!

However if you can come to an arrangement with Beobuddy then I think that would be best in this instance, amplifiers are unforgiving at the best of times, and you don't want to take a step back at this stage!

Hope you sort it out :-)

Yes the print is very delicate with these amps, which is why I suggest not to remove the processor can unless absolutely necessary! I guess he is very lucky things were not worse!

Well done Beobuddy :-)

Thanks to Beobuddy the BM is working beautifully once again.

I think Martin was right in telling me in the beginning not to try repairing this machine myself. Rebuilding the amp is one thing, but there are just so many other things that can go wrong or break. Without the proper equipment and knowledge it is pretty much impossible to fix it when that happens, so you're better of leaving this kind of job to a professional.

Did the amp survive new years eve? 😁