marexy wrote:

I have a problem repairing Beolab 4000. Super nice speaker, with a common problem of older versions. The speaker works great via the Powerlik connector. The problem is with the RCA connection. The speaker works normally when it receives a signal. The problem occurs when the speaker goes to ST-by after 2 minutes. As soon as it goes to st-by, it turns on again in a few seconds, and turns off in 2 seconds. This rhythm is repeated. I've already looked at all the connections, measured the transistors and resistors, but I can't find any faults.

something on this topic has already been written, and I have tried just about everything, but I have not found a hidden error :(

Thanks

Hi

Same cables for both BL 4000 i try...and no problem with other BL 4000.

After an hour of checking components no progress :(

found that post : 

This one is tricky.

I have spend some time on this and measured with a scope at several points at the same time.

It has to be with the descending voltage across IC1. The plus and minus voltages are not descending equally. That causes at the entrance (!) on pin 3 a burst, which  triggers the autostart circuit. When you lift pin 3 from IC1, then the BL4000 shuts off and doesn't start again.
But that isn't the solution, simply as IC1 is the first IC in line of the complete audiocircuit.

I've changed IC1, but made no difference. The lifted pin 3 still generates that burst.. Trying to help both voltages to descend equally wasn't successful either.

Btw, my BL4000 had no foam issues, like the ones with the black deteriorating foam. 
Will be continued as the others haven't mentioned the solution either. 

Yesterday i replace all SMD transistors plus some resistors.. and no luck..still same error :(

keep you posted..

Parts-firing is that called.... Could have told you on forehand that would not work. Unless it's a left version with old foam. Then there have to be replaced several smd parts.
But again, I have a board with the same symptoms, is clean and unaffected by old foam. Serialnumber starts with 18xxx.

Due to more urgent repairs I've replaced to board to minimize the waiting time for the customer. So, it doesn't have my priority at the moment.  

Thanks for answer :)

my BL4000 is serial No 1302.... so old MK1..with rottern foam problem :(

I clean all rotten foam problem an do some additional work as i wrote..but no luck.

so any additional suggeston will help :)

What parts should i repalace in addition to that what i allready done ?

As you are expert, i am sure you did see many of different erroors on these spekers.

It is interesting as weel that both black speakers are not same black colour ..hmm :)

After some time i decided to try fixing that BL4000 again.

I check many components and not find any error... :(

Problem is noly when speaker is in position LINE in.

Onposition PWL is all ok.

I think problem is in voltage regulation for automatic ON -OFF.

So any hint..repair trick or magic stick will be welcome :)