hamacbleu wrote:

(It's getting old and hot in there because of the power supply).

What's wrong with the power supply since the amplifiers get hot ?

Martin

What gets hot in mine is only the display circuit!

The amps hardly ever get more than lukewarm.

My guess is a contact/solder problem of some sort. Trace the signal!

My came back from servicing with the same problem !

Sorry but my technician is in holyday during august and will work on it again in september to fix the problem. As he test all the electronic part of the amp (everything seems to be perfect), I think it could come from speakers socket (they are quite loose in my BM).

Do someone know if there is a separate amp for headphone in the BM8000 ?

I'm interested to know if you find a solution. When I will fix the problem, I will also post the answer.

BR,

Jacques

Thanks to all,

No, the amps are not getting hot at all. I just meant that since the power supply and display circuits are just below and above the right output amplifier, maybe that the board ages more badly than the other side. After a few hours, its getting somewhat warm above the display fins... as a comparison, It appears to me the the heatsinks of the amps, after the same time spent, seems to display much less heat that these ventilation fins...

Yesterday I let the amp plays and tried to understand what was happening. The distortion occurs at about 3.8 and up, and only if I turn the encoding wheel real fast. if I go slowly, it's stays fine.

My assumption is a broken solder joint or, a failing transistor.... But if it would be a failing output transistor, wouldn't the sound be distorted too in the headphones output: it's not... (when the speaker switch is off)

Probably a broken solder joint: I don't know how time this machine spent in a box before I acquired it. Now that I use it frequently, maybe weaknesses starts to appears. And it's probably not the only one I'll met...

I'm not ready to open it yet but I will post photos and explain what I've done on his thread when I'll do it.

Thanks to all...

To Jacquesboo: from what I understand, the output for the headphones comes from the same source but it probably drives much less power than a speaker. (Please, somebody, correct me if i'm wrong!)

Guillaume

Is that channel louder than the other channel when distorted? Sounds like a funny fault! Maybe you don't get it in your headphones becuase they don't have the range, or perhaps because they are not loading the amplifier - try headphones at same time as speakers if you can isolate the sound from each...?

Step1 wrote:

Is that channel louder than the other channel when distorted? Sounds like a funny fault! Maybe you don't get it in your headphones becuase they don't have the range, or perhaps because they are not loading the amplifier - try headphones at same time as speakers if you can isolate the sound from each...?

No, they are at the same level... When I put it to spec 3 months ago, I've put the offset outputs dead down to 0V. Both channels shows now, after a 1 hour run, 6m V. Not that bad I suppose, maybe a little above the prescribed 5m V, but it does not seem to be the problem.

As for testing with the speakers on, it's really hard to tell since I hear the distortion coming from it at the same time. I'll try with the speaker against the wall with a cushion in front of it! But I suppose it will be distorted since it's loading from the same source?..

...Just saw in the technical manual that Jacques posted a few months ago a whole chapter on "supression of noise spike from the volume control" Maybe it will lead me somewhere..

...Hmm that chapter leads to the preamp.. I haven't changed these caps... but if it would be the case, the sound would be distorted too in the headphones isn't it..?

Guillaume

Just came back from work in hope to make some test with headphones, as mentioned by Olly...

Of course, I can't make any test... the problem has completely disappeared !

It reminds me of my cdx that was only working above 21 celcius.. until I reflowed every griplets

I'll have to open that thing again someday, probably a solder joint of one of those two #$%$# BF857, or that row of resistors.

I'm happy however it's not the left output amplifier as i'm a "Beomaster 8000's left side" hater...

Thanks to everyone for your inputs

I'll keep you informed of the progress

Guillaume

The problem becoming more permanent, I decided yesterday to have a look at the right output amplifier. With a magnyfing glass, I was happy to find some joints that would soon become problematics... I reflowed them  and check for their good continuity afterward...

Sadly however, the problem is still there. I noticed that if at startup the volume is set relatively low (2), and then cranked up really slowly, the distortion does not occur and the sound stays good (until it goes 4 +, but I never put it that loud).

I tried the test with headphones: can't hear the distortion in them, but it's really hard to tell even with the speaker turned against a wall...

My present assumption is that maybe an output transistor is failing: When I first acquired the beomaster, last year, it was sold with the "right side too hot" problem. Maybe some of them badly aged, giving me the current problem... A big job that i'm not ready to tackle yet...