Defect capacitor on JBL 4344 ??

[Madien3388]

Hi,
I recently replaced the binding posts of my 4344 and discovered that one capacitor has a strange aspect when dismounting the filters.

I have been told that all capacitors of this JBL monitor were in polypropylen, not chimical ones. Only chimical capacitors flow when they are dead, so it shall not be the capacitor but the glue used to stick the capacitors on the filter?

If anyone would be able to help me on this, it would be great. To know if it is only the glue which has flown under the capacitor or if it is the capacitor which is dead. I'm started to worry ...



Many thanks in advance !

[Chas]

Bonjour Madien 3388. Actually, I believe the capacitors were Mylar in the 4344/4345 networks. When I looked your pictures at first, I thought it was simply the hot glue used to secure the cap running down the board. I have never seen anything like this oozing from this type of capacitor construction. the ooze is a different colour than the glue.

You could remove it and measure it. Or better yet, simply replace it.

[Madien3388]

Bonjour Madien 3388. Actually, I believe the capacitors were Mylar in the 4344/4345 networks. When I looked your pictures at first, I thought it was simply the hot glue used to secure the cap running down the board. I have never seen anything like this oozing from this type of capacitor construction. the ooze is a different colour than the glue.

You could remove it and measure it. Or better yet, simply replace it.

Thank you Chas! I am quite lost as polypropylen capacitor doesn't do that when they are dead.
The liquid is very solid, like the glue under the capacitors. Liquid from chimical capacitors is not so solid, more sticky.

I am quite afraid to remove it as it seems that the speaker works great... but it bothers me much !

How could I know the type of the capacitors ? Polypropylen or not ?

Where can I find the 4344 schematics to find out the function of this capacitor (is it used for the 2235, 2122, 2421,2405 ?)

Many thanks
Damien

[jcrobso]

http://www.mcmelectronics.com/product/50-4566

[Ian Mackenzie]

Looks like Alien goop!!

Its a shunt capacitor in the horn filter.

I would be inclined to leave it alone unless the substance is effective / contaminating other components.

Ian

[mech986]

3144 network, charge coupled version.

http://www.audioheritage.org/vbullet...25&postcount=5

[Madien3388]

Thank you so much for your help, I really appreciate that !

What is the function of a shunt capacitor ?

If the capacitor was in fact damage and not working normaly, what kind of impact could I notice on the speakers response (I have a measurement device which can measure the sound produced by the speakers)

And sorry but what is the meaning of "goop" ?

Thanks JBL fans

[Ian Mackenzie]

Thank you so much for your help, I really appreciate that !

What is the function of a shunt capacitor ?

If the capacitor was in fact damage and not working normaly, what kind of impact could I notice on the speakers response (I have a measurement device which can measure the sound produced by the speakers)

And sorry but what is the meaning of "goop" ?

Thanks JBL fans

Goop is Alien snot!

Do a search on 3145 crossover schematic

Compare one box to the other.

If both are gone find replacement for both (do both anyway), perhaps a mid price part from Parts Express or a Kimber Cap from Sonic Craft and replace the same part in both crossovers

I put together a whole thread on this a while ago

http://www.audioheritage.org/vbullet...over+pictorial

Upgrade/repair thread

http://www.audioheritage.org/vbullet...769#post178769

That is will cost to a slab (of Victoria Bitter)!!

[Chas]

Hmm...I just might have all the JBL OEM capacitors I changed out of my 3145/4345 networks somewhere at home.

[Madien3388]

Thanks Ian ! I have already checked both filters. Only one has this goop under the capacitor. All other capacitors seem fine.

Is it possible that this goop comes from the capacitor itself? normally, polypropylene capacitors doesn't do that as they are made of metallic films. If the capacitors are really in polypropylene, it can not come from them, can't it ?

I take a lot of care of my vintage JBL speakers and want to keep them for a long time. I have already changed the binding posts for better ones; but I am very afraid to intervene on the filters. I do not want to do worse. What is the exact value or reference to use, and where to find the glue to stick the capacitor on the filter?

I have had a look on your links. It is very impressive. Is it possible to find such 4344 filters already tweaked ?

I really appreciate your help
Best regards from Paris
Damien

[Ian Mackenzie]

Now them things are priceless.

[Madien3388]

Link to capacitors adviced by Ian, if it can also help someone else

http://www.soniccraft.com/kimber_capacitors.htm
In my case, it would be this one if I am not wrong : 1.5µF /

3µF / 200VDC 0.70 x 1.68inches $11.94


I have also found this in Auricap: http://www.soniccraft.com/auricap.htm
3µF / 200VDC 0.90 x 1.00inches $19.44


But I am not an expert at all in filter components and tweak, so I do not know the differences between the 2 model.

[mech986]

Assuming you are not the one and only original owner, do you know if any previous owner may have done some work inside the speaker? The residue that is sort of a yellow drip on the end of that capacitor looks suspiciously like yellow wood carpenter's glue (PVA glue).

If the crossover had been removed or worked on and the capacitor hit or moved, it may have come loose from the original semi-clear adhesive (possibly hot glue?). Maybe the original capacitor was blown and a new JBL cap (looks like it was sourced from a similar batch as the other large caps) was installed later with regular glue?

As far as I know (AFAIK), all JBL crossovers of that era used Mylar (polyester) film caps with small polypropylene bypass capacitors.

bart

[mech986]

Original 3145 schematic, need to magnify the pdf to see well and some of the component values are difficult to read.

http://www.jblproservice.com/pdf/Net...%20Network.pdf

[Madien3388]

That is very interesting Mech986. Thank you! I didn't notice that. Indeed it is a possibility. The capacitor seems a little longer than the one in the filter of the other speaker (I have attached a picture of it). So it may have been replaced, but it seems that an original Mexico capacitor was used.
What is strange is that the glue under all capacitors has the same colour, and the other capacitors don't seem to have been replaced.
It is quite a mystery.
I think I'm going to buy the spare capacitor, just in case and will wait a little before repacing it.

One question please: Can "Mylar (polyester) film caps with small polypropylene bypass" capacitors produce this liquid when they are dead, like chimical capacitors ?

Or, if it possible, I will find other crossover filters with "up to date" components...
What do you think ?