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Beolab 4000 questions - foam rot

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h1npw
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h1npw posted on Sun, Mar 5 2017 2:06 PM

I'm looking to buy a couple of pairs of these great speakers from flea bay... Can anyone tell me 

1) How can you differentiate between those with the black foam inside them that eventually turns to goo, and those with the "stable" white foam, without asking sellers to take their speaker to bits?

2) Did they change the foam when they started production of the Mk2?

3) Did the serial numbers continue in sequence from Mk1 to Mk2?

4) is there a specific serial number point when the foam changed?

Any info will be greatfully received!

Cheers

Nigel

 

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GregKo
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Nigel -

 

The differences between MK1 ad MK2 are much easier to identify than serial (product) numbers 

 

MK1 has an RCA line level input on the back in addition to powerlink, MK2 does not, it's powerlink only.

MK1 has the illuminated power switch on the front of the cabinet (red/green) MK2 is a light only, not a switch.

 

MK1 is type 6638

MK2 is type 6644


The product number is on the front of the speaker behind the grill (fret) beneath the woofer.

 

Also keep in mind that MK1 is a traditional class A/B bower amp whereas MK2 is class D Icepower

 

Greg

Beocenter 9500, Beomaster 6500, Beolab Penta MKII, Beolab 5000, Beolab 3000, Beolab 4000 MKI, Beolab 4000 MKII, Beogram 3300, Beogram 3000, 2X Beolink 7000 RDS, 2X MCP 6500

Steve_torque
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Hi Nigel,

My advice would be...if you can just get them from a reputable pre owned B&O company, like lifestyle av or morethanav etc in the UK. You then get a warranty and peace of mind that they have been given the once over. With added bonus of not paying much more for 4000's, if anything. That's what I did for my 4000's.

I think lifestyle av do sell through eBay, but just get in touch.
marexy
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Hi

MK1 all day long :)

For me MK1 it's way better than MK2.

Why ...RCA line out, switch if you want to cut power, nice soft soud!

Drivers are the seme.

And repair cost of MK1 are low.

Used MK1 are half the price of MK2.

 

 

 

h1npw
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h1npw replied on Sun, Mar 5 2017 4:50 PM

Thanks guys, but you haven't really answered my questions!

I've done a bit of digging since i first posted my questions and have found the following

Serial number 13789500 had the black stuff that turns to glop.

Serial number 18947009 had the white foam.

Both of these are Mk1. Both type 6637

So, they changed the foam before the Mk2s came along.

It would appear that the best type to go for are MK1s because of the price & sound, but with the white foam  

There must be a specific point in the serial number sequence where they changed the type of foam used!

 

Cheers

Nigel 

 

 

marexy
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serial no 13...14 ...have black foam...that go's to glop :)

Serial 18... have white ...

price is the same or minimal differnece.

Yes ..both are MK1

 

 

Beobuddy
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Somewhere around 15 or 16 new white foam has been used. 

The same counts for the BL8000.

StKong
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Beobuddy:

Somewhere around 15 or 16 new white foam has been used.

The same counts for the BL8000.

I have four BL4000 of the 14xxxx serial. Before this thread I was unaware of whether to open them in order to remove the foam. Now, I have a new project.

Thanks!
h1npw
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h1npw replied on Sun, Mar 5 2017 9:58 PM

Quick way of checking is just remove the 2 screws that hold the tweeter in place and lift it up -  you can see what colour the foam is.

Cheers 

Nigel

StKong
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StKong replied on Sun, Mar 5 2017 11:45 PM
h1npw:

Quick way of checking is just remove the 2 screws that hold the tweeter in place and lift it up - you can see what colour the foam is.

Cheers

Nigel

Thanks, Nigel. Do you have any foam removal experience?

Opinions seem to vary on whether its is necessary to replace the foam.
marexy
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Yes ..you should replace the foam so that the sound will stay as it is.

Clean ALL parts and inside from old foam on the PCB boars!

You can use fome simelar to what is inside. do not buy original ..to expencive.

h1npw
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h1npw replied on Mon, Mar 6 2017 7:47 AM

Hi StKong

Yes I do, but I haven't been very successful!

The speakers are very easy to take apart. The pair I did the foam was part OK,  part turning / turned into goo. It's horrible stuff to get cleaned off. I say not very successful as after I'd done the job, one of the speakers doesn't work! Hopefully I will be able to get it repaired. I don't regret I did it - when you see the goo common sense tells you it has to come out!

Cheers

Nigel

Beobuddy
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h1npw:

It's horrible stuff to get cleaned off. I say not very successful as after I'd done the job, one of the speakers doesn't work! Hopefully I will be able to get it repaired. I don't regret I did it - when you see the goo comman sense tells you it has to come out!

 

It's not uncommon that by removing the old foam, you've taken the topsurface also of one of more parts inside.

Often I hear that after buying and transporting one of the BL4000's stopped working. Caused by shocks during transport, the foam moves a little inside the cabinet.

 

StKong
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StKong replied on Mon, Mar 6 2017 11:25 AM
Beobuddy:

It's not uncommon that by removing the old foam, you've taken the topsurface also of one of more parts inside.

Often I hear that after buying and transporting one of the BL4000's stopped working. Caused by shocks during transport, the foam moves a little inside the cabinet.

That would speak for disassembling in situ rather than loving them too much.

Does anyone know if certain factors expedite foam decomposition, such as heat or humidity?
marexy
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marexy replied on Mon, Mar 6 2017 11:53 AM

Does anyone know if certain factors expedite foam decomposition, such as heat or humidity?

- bad material, not tested enough and after 15 years ...it's like that.. :(

i have repair more than 20 pairs ..and it's no problem.

Take apart  spekar

remove, fret, drivers, plastic front, transformator board, remove ALL rotten foam,clean ALL foam left overs on PCB boalrds!!!... with gasolin or isopropanol ( hand desinfective )..

be carefull ...do not spill ..do it wih ear cleaners :)

add new foam...or like..an than put together in reverse order.

spekar not working...than..

if there is fault on PCB you must check SMD conection on amplifier board on the spots where had beed rotten foam!!

that is all.

B&O service will take 200€ for that job...OMG... :(

 

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