Now i do have some problems as i have no additional PCB's for more testing and trying to find best way and alternative to fix different errors on that PCB.

So if any of you have faulty, broken, not working or partial working PCB would be happy to buy or if you wish to donate them for ""for scientific purposes""  :)

My shipping costs. 

If any of you wish to repair it by DIY you need SMD heat gun + smd soldering iron with reguleted temperature.

Hi Jean

Yes...bl4000 Mk2 have the same boards.

There are no PCB Shematics....as i know of...

Maybe some inside B&O info will help...hmmm

In 50% ...maybe 50%... it is ok to change mosfet ST9F3LL but only with the same one as till now i did not find any other option to work and all 4 per clanalle should be changed. And i do not have datasheet for ST9F3LL.

10 ohm change if broken...no need if it is ok.

In many cases there are faults on the top side of board or bad connection inside board.  Note....Repair only with correct smd tools.

any other questtion..PM me

marexy wrote:

Hi Jean

Yes...bl4000 Mk2 have the same boards.

There are no PCB Shematics....as i know of...

Maybe some inside B&O info will help...hmmm

In 50% ...maybe 50%... it is ok to change mosfet ST9F3LL but only with the same one as till now i did not find any other option to work and all 4 per clanalle should be changed. And i do not have datasheet for ST9F3LL.

10 ohm change if broken...no need if it is ok.

In many cases there are faults on the top side of board or bad connection inside board.  Note....Repair only with correct smd tools.

any other questtion..PM me

 

Thanks a lot for your very valuable advice!

Also, should I replace all ST9F3LL mosfets, or once the defective one is found I can leave the others in place? Are they failing because they don't age well or because they are used near their limits?

Regards,

Jean

I think the correct FET's devicename is STS9NF3LL

B&O has switched from STS9NF3LL to FDS6294 in later production of the pcb

Hi

Try to change only bad one but ...it is better to change all 4 on the same side.

Hemenex ..thanks

Yes it is correct datasheet.

If you check item TS7NF60L it is not so differnt but it is not ok ..as heating badley fast.

If you put finger on ti when speaker is working  and it is open...you can feel it, so from my point of wiew it's not safe to use it.

There are some WWW pager that offer "" original" parts ..but i tihk all are fake.

""Also, should I replace all ST9F3LL mosfets, or once the defective one is found I can leave the others in place? Are they failing because they don't age well or because they are used near their limits? ""

Yes ..maybe they are used near their limits..can't say without shematics and correct service manual.

Or just generaly poor design of PCB from start.

plus i'm not el.rapir geek to be smart and i can give only my point of perspective.

i learn much on these project :)

It's not over yet as.. will try different end-mosfet and some other tweeks log the way.

all done :)