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Beolab 4 repair , fix it, bin it,It's worth it ??

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marexy
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marexy posted on Tue, Sep 3 2019 7:19 PM

but what  IF ..

 

 

 

First of all, I welcome all forums members and users of that  and ozhers B&O products.
Like many of you, I purchase quite a few units during years and after some time some of them needs attention. some more some less..
But most of all, I want to bring to life the Beolab4 speakers.

As my darling wife like to listen to them in office :)

Why 4 broken pcs. Ok…2 of them I purchase from collegue and they work for 2 years then die…ende, vege, game over


And than I purchase oline 2 in perfect condition…yap…you wish…one work for one month and the other for 3 month..

 

And the reason of course....taaadaaaa

 

 

 

 

The amplifier board is defective in all of them.
This is also the reason for 95% (or meore) off all errors on these speakers.


Let me highlight the purpose of this post.
Simply, an astronomical price for a spare part that is over € 100 a piece.
With an official B&O service shop 130€ + labor which I find shameful for such a small piece of electronics PCB board.
A friendly user and a true expert on these forum offered me a reasonable price, but it is still too high and un- economical for me.
Let me clarify.

It is not economical to repair on component basis, for customers, because it is too time-consuming and you can not give as much warranty as for new one plus you can not firnd original MOSFET ST9F3LL any more.

In addition, you can actually buy a pair of used working speakers for around € 150. to 250€ .so the same price as spare PCB amplifier borad.

So the repair is not theoretically and economically worth if you not do it for your selfe.
But since electronics is one of my hobbies and relaxing my nerves after a busy day at the company, it will be a bit of a challenge for me to have a little education and a joy to repair. In this modern world where repair is already economically unacceptable, I find all this sad.
Everybody throws away things that can actually be fixed ( ok..some more some less )
I will write this post in stages as I find the time, the moment of inspiration, and the spare parts.
I also hope for your help if you have any broken PCB’s to donate for my experimentation :)

You can find 2 photos of that PCB.

on fist photo you find  some sound processors and on the other MOS transitors that are usuly faulty.

also 10 ohm resistor is damaged and some transistors in the area.

I did fix some of that power boards to my friands but i can not be 100% that they work for long time.



 

 

 

 

 

 

 

 

 

 

 


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MCB
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MCB replied on Tue, Oct 8 2019 7:45 PM

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

marexy
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marexy replied on Wed, Oct 9 2019 10:21 AM

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.

 

 

 

 

 

marexy
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marexy replied on Wed, Oct 9 2019 10:36 AM

""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.


marexy
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This is a PCB that came back from the official B&O service where they said no repair was possible and returned the customer in such a robbed state.
They probably repaired the original and sold it to another curstomer who was willing to pay the price of a new one.

Anyway....

After few hours of playing and smd soldering, tuning, .. i can say ..It's alive and working :)

i learn much on these project :)

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

 

 

 

 


marexy
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marexy replied on Tue, Oct 22 2019 8:42 AM

all done :)

I successfully repaired all faulty-broken PCB's in stock.
They successfully passed the 48 hour nonstop playing test.

Project completed  :)

 

Michael
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Hey guys! Interesting thread!

I have a V1-40” where one channel suddenly was distorted on higher volume levels. It’s the left tweeter.

I took the unit apart and found the three speaker setup uses two custom icepower boards each with two 32W amps.

One board utilizes just one channel. The left board where the issue lies uses just channel “100” closer to the board edge on the output port side.

I was thinking about trying to switch it to use the other channel and thereby relieve the issue entirely (hoping that the other channel is free of issues).

However, I’m still curious to why this has occurred and started looking at the chips and layout. It seems to have much in common with the beolab4 boards and if so it might be worth looking closer at.

AFAIK it seems it uses almost the same circuit as B&O dis on the Beolab 4 pcb and I read here that they changed to another provider that might be better.

I’m including photos here of both sides to let you guys have a look and possible advice me on what I can and should do. Hope that’s okeySmile.

marexy
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marexy replied on Sun, Oct 27 2019 8:28 PM

Hi

i think...it's 85% the same as BL4 or BL4000NK2 board

try to check resistors closest to M3307 / 8pin chip and check 2 mostet transsitors in the same area.

If that is ok..check all resitors in the board.

 

 

Michael
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marexy:

Hi

i think...it's 85% the same as BL4 or BL4000NK2 board

try to check resistors closest to M3307 / 8pin chip and check 2 mostet transsitors in the same area.

If that is ok..check all resitors in the board.

Hello Marexy,

What do you mean with check them? I found that the PCB is called "35" or 8004783 anad that the Beovision 11 has the same boards. It seems to be an iteration on the BL4 and BL4000mk2 amps. 

I would like to try and change to use the other channel that probably isnt faulty. Do you think that could be possible and if so, which pins should I rearrange?
It seems FP1,2,10 and 11 on P1 is connected to the main logic board, as is the free cable connected to P3.

Michael
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Michael replied on Sun, Oct 27 2019 11:44 PM
I managed to make it work! I measured all the pins and some other things to figure out what they do. Then I simply switched pin 1-11 and 2-10 on the input. And moved pin 1->3 and pin 2->4 on the output to make use of the input and output that was before unused.

It seems to work perfectly! I’ve been doing some tests and it all is fine and sounds lovely.

Why the other amp channel started distorting is something I will leave for now and I’ll re-assemble the tv again tomorrow after some more tests.

Thanks for the advices here too!

Aussie Michael
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Michael:

I managed to make it work! I measured all the pins and some other things to figure out what they do. Then I simply switched pin 1-11 and 2-10 on the input. And moved pin 1->3 and pin 2->4 on the output to make use of the input and output that was before unused.

It seems to work perfectly! I’ve been doing some tests and it all is fine and sounds lovely.

Why the other amp channel started distorting is something I will leave for now and I’ll re-assemble the tv again tomorrow after some more tests.

Thanks for the advices here too!

Very nice outcome
jvezina
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Just to give an update on this issue.

I decided again to go the easy way and I had the board replaced as they are still available from B&O. Nevertheless, I bought replacement ICs from Digikey as spares as they are still available from them even if they are obsolete. If the amplifiers fails again in the future and are no longer available from B&O, then I will try to repair them.

The official part number is indeed STS9NF3LL and the chip is marked 9F3LL as the others before.

Marexy, if you have time, could you write a short step by step procedure explaining how to diagnose the problem on the board and upload it to the service manual section of the forum. I did the same a long time ago about capacitor replacement for the North American MX 5000.

Best regards,

Jean

 


marexy
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marexy replied on Tue, Nov 19 2019 6:38 AM
I can only give indicative guidelines as I have already described...sorry

The error is not always the same and the diagnosis of the error is not always 100% successful.
Maybe i was lucky.

Since there is no service plan, it is less or more a guessing and experience of repairing the units in the past.
Nor am I convinced that the repaired unit will work successfully in the long term.
In addition, you need at least an amateur tool to repair SMD components and the right templature for repair, because quickly something goes wrong with improper handling. plus ..soldering microscope helps so much :)
It is necessary to know the basics of electronics and to know the components and their task.



 

jvezina
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Thanks a lot,

Jean

ipaul
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ipaul replied on Thu, Nov 21 2019 9:00 PM

Hi all, coincidentially, i am also working on those now.

I kept defective in the past and have 5 now.

All had other defective components apart from some fets: resistors (the big and/or small 1K5 apart from the 10R) and even smd transistors on the opposite side of the fets.

Anyway, the challenge still is the fets.

With a bit of luck the replacement module is still available for around 60 euros (that used to be the price here) and i hope to see if the newer types use the FDS6294 fet as a direct replacement.

On a Dutch general repair forum there is also someone working on this, let's see what we can figure out....:)

 

 

marexy
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marexy replied on Fri, Nov 22 2019 11:54 AM

If you decide to sell PCB's let me know :)

 

 

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