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BHGA
06-07-2011, 02:24 PM
I have apair of JBL 240Ti. One day one of the LE41H-1 woofers where stuck!. There was sound but no movement. I could push in the cone using allot of force, and it wery slowly came out again. No voicecoil rubbing sound at all. Strange. Took out the unit and, yes it was stucked, and nothing wrong to see.:confused: To bad, the cone had to come out. I managed to loosen the diagphrame from the foamedge by hand. Then I used som aceton on the spiderglue and so with a screwdriver I carefully got the spider loose. Then some desoldering and so I slowly forced the cone out. I saw the typical JBL white hand writing at the diagphrame said year -85.

Ahh-then I saw it. At the inner end of the magnetventing hole, there was glued a pad of foam over the hole. Proably to stop dirt to enter the magnetic gap. The foam was rottened and pieces had fallen into the magnetic gap and acted like glue in there. No wonder the voicecoil didn’t move. JBL- why did you use that crap foam matrial?:banghead:
Then I cleaned the alu voicecoilform inside carefullywith aceton. Checked and cleaned the magnetic gap as good as possible. Tried the cone in the frame agin and it feels ok. No glued feeling.:D

Now I have two challenges:

1: When will the same happen to the other woofer? I have to take away the foam before it falls apart. How? :dont-know:

2. I have done refoaming but not reconing. I have the sentering ring for the LE14 from a friend. But I don’t know how to remove the orginal JBL black glue that holds the dustcap. Aceton is not softening thatblack glue. Yes, I am reading about carefully knife cutting and new dustcaps,but is there no way to loosen that black glue?

If I find a good way to take of the dustcap I probably have solved nr.1 challenge.
Regards BA

Earl K
06-07-2011, 04:10 PM
Now I have two challenges:

1: When will the same happen to the other woofer? I have to take away the foam before it falls apart. How? :dont-know:

2. I have done refoaming but not reconing. I have the sentering ring for the LE14 from a friend. But I don’t know how to remove the orginal JBL black glue that holds the dustcap. Aceton is not softening thatblack glue. Yes, I am reading about carefully knife cutting and new dustcaps,but is there no way to loosen that black glue?

If I find a good way to take of the dustcap I probably have solved nr.1 challenge.

- Yes it's a disgusting situation in that JBL essentially designed in " planned obsolescence " to these magnificent woofers .
- All the Pro Woofers ( 2225, 2235, 2204, 2245, 2240 ) from that era have the same problem . SOMEONE really needs their butt kicked .

Anyways ; MEK ( methyl ethyl ketone ) (http://en.wikipedia.org/wiki/Butanone)should loosen the glue line around the dust-cap .
Use this product very sparingly since getting any on the voice-coil is a no-no .
Best to use it outside or in a well ventilated place . I figure you can probably get in it Norway ( since you aren't subject to as many EU regulations on VOCs, as some of your southern neighbours are ) .

- Now is the time to rebuild both those le14h-1 woofers starting with new foam surrounds ( purchased from Rick Cobb (rcobb@tampabay.rr.com) , ie; looneytune2001 on eBay) & then fixing the vent-foam problem that you already discovered .
- The ( disintegrating) foam over the vent hole should be replaced by something porous ( & tough ) such as thick plastic mosquito mesh ( glued in place ).


- I'd probably lift both cones out of the baskets , replace those bad foam vent-filters, replace both surrounds & and then take it all to an experienced reconer to reassemble .

<. EarlK

1audiohack
06-07-2011, 07:44 PM
If the dust caps are fixed with instant adhesive, and many are, I know of no solvent that will disolve it.

If you cut the cap off as close as you can to the glue line, the new cap will usually sit right on top of the old glue line, a careful glue job can result in a like new finish possibly not discernible as re-done.

JeffW
06-07-2011, 08:30 PM
Nitromethane will dissolve CA (super glue), and you can buy CA debonder from stores that cater to model airplanes. The best debonders are nitromethane based, but today the acetone based (that suck) varieties are more common and less expensive.

1audiohack
06-07-2011, 08:33 PM
Thanks Jeff, that's good to know!

subwoof
06-08-2011, 07:28 AM
the black glue from that age ( 26 years ago ) will put up a real fight - I find the best method is cutting off the cap right at the glue line with a quality razor blade / knife and like posted, a new cap will drop + glue over it nicely. sometimes you can break the glue bond to the paper and take it out piecemeal but beware of removing cone material.

Yeah - ANY woofer that comes in here that's used gets the cap and filter replaced...and if it's a foam surround, the kit is removed ( like you did ) and re-assembled at the JBL service place with new foam.

skol