JBL 035Ti repair

[spirou38]

Well, I think that's the problem then. It shouldn't have been glued. There are four bolts that hold the motor to the diaphragm. The arrows show where these bolts bolt into the magnet assembly.

Maybe there were glued versions but I've never seen or heard of one as such.

Does yours look different?

No, my one doesn't look different ... but have a look to the following picture and you will see that there are 2 metal parts : the one with the 4 screw holes should be glued on the magnet itself. Note that you can see the glue marks on both metal parts. Of course the metal part that is attached to the plastic diaphragm part is not glued on the plastic.

...

Is there a person that has a picture of one with the engine broke off? I am going to take apart my burnt up one tonight and look for glue...

Here it is

...

[BMWCCA]

Are those your L80Ts?

Are they black?

[mech986]

Ahh, the front plate with attached dome/voice coil screws down to the top plate which is glued to the magnet which is glued to the pole piece/back plate. What happened is the magnet came unglued from the top plate which is still screwed to the front plate.

Somehow can't imagine the voice coil is still round with the pole piece falling out unless the pole piece fell straight back with the speaker on its back (like if the package was dropped). But typically there needs to be a shear force at 90 degrees to break the glue?

Looks a lot like one of Scotty's drivers that lost its magnet.

[spirou38]

Are those your L80Ts?

Are they black?

Yes they arrived last week and as you can see, they are black .

When I was young the L80T were my first JBL speakers. I bought those for my grandson who is 10 years old. He must know what are JBL speakers.

A few hours ago I won a couple of 035TiA on eBay. They will replace both 035Ti .

But I will repair the 035Ti : I will try to find a non metallic pipe of appropriate diameter for centering and gluing the to metal parts. Then just put the diaph in the centering pins and 4 screws.

[spirou38]

Ahh, the front plate with attached dome/voice coil screws down to the top plate which is glued to the magnet which is glued to the pole piece/back plate. What happened is the magnet came unglued from the top plate which is still screwed to the front plate.

Somehow can't imagine the voice coil is still round with the pole piece falling out unless the pole piece fell straight back with the speaker on its back (like if the package was dropped). But typically there needs to be a shear force at 90 degrees to break the glue?

Looks a lot like one of Scotty's drivers that lost its magnet.

Yes mech986, I think you are right : some marks inside the packing show that the L80T fall on its back. And it seems that the shock was violent. Fortunately the packing was very good and there is no other damage than the 035Ti and the voice coil is still round and perfect ; I measured it with a digital "pied a coulisse" - I don't know the English word but I included a picture hereafter.

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[pos]

Are those your L80Ts?

Are they black?

There is a "lacqueur" serie that is black:
http://lansingheritage.org/html/jbl/...7-lacqueur.htm

But I think the one Spirou has is a L80T GI that shows up often on ebay Germany. It is mat black.

[spirou38]

There is a "lacqueur" serie that is black:
http://lansingheritage.org/html/jbl/...7-lacqueur.htm

But I think the one Spirou has is a L80T GI that shows up often on ebay Germany. It is mat black.

you are right my L80T GI come from Germany

[ratitifb]

But I will repair the 035Ti

only hoping you are able to well centering all parts with magnetized motor and there will be no irreversible magnetic losses due to "air gap re-gluing" and/or reluctance change

[BMWCCA]

I think the one Spirou has is a L80T GI that shows up often on ebay Germany. It is mat black.

Appears to have a finish similar to the L7 and that series. Seawolf's favorite "black ash".

Interesting. I've seen the lacquer "BQ" series brochure in the library but never a matte-black version. Spirou, more pictures when you get them back together? Thanks.

Hmm. I'd buy these: http://www.marktplaats.nl/index.php?...-speakers.html

Another pair here: See if this link still works: http://74.125.47.132/search?q=cache:...&ct=clnk&gl=us

If not, maybe these will hang around:

[spirou38]

Appears to have a finish similar to the L7 and that series. Seawolf's favorite "black ash".

Interesting. I've seen the lacquer "BQ" series brochure in the library but never a matte-black version. Spirou, more pictures when you get them back together? Thanks.

Hmm. I'd buy these: http://www.marktplaats.nl/index.php?...-speakers.html

Another pair here: See if this link still works: http://74.125.47.132/search?q=cache:...&ct=clnk&gl=us

If not, maybe these will hang around:

My L80T GI seem to be in a better shape except for one tweeter.

I will put some pics when I will receive the 035TiA.

[spirou38]

Looks a lot like one of Scotty's drivers that lost its magnet.

Hi everybody,

Good new Yesterday I tried to repair the 035Ti.

First of all, I took some measurements and found that the diameter difference between the "cylinder" that is centered in the magnet ( called polar part ??? ) and that goes in the hole of the ring ( that was unglued from the magnet ) and the hole of the ring was exactly 1.6 mm.

So I looked after some 0.8 mm non magnetic parts and found some plastic that was exactly 0.8 mm thick. I cut four 16 mm wide parts . Those plastic parts can easyly be bent.

Then I inserted the 4 plastic parts between the magnet and the cylinder inside the magnet, put some cyanoacrylique glue on the magnet ( taking care that there will not be some glue in the centering holes and screw holes of the ring when gluing the ring ), and put the ring that because of the plastic parts automatically centered itself.

Of course I first tried without glue !

I waited 24 hours so that the glue could dry. Then carefully mounted the diaphragm and put the 035Ti in the L80T.

Great sounding, no difference between the good one and the repaired one, no rubbing coil sound . I hope that will last for a long time ...

Unfortunately I forgot taking pictures. I hope you could understand the process.

Here is a picture of that kind of plastic parts :

If somebody needs of some of those plastic parts for repairing a 035Ti ( Scotty ??? ), I can supply some.

[ratitifb]

Actually you applied the shim method to center the voice coil with four pieces of plastic of suitable thickness.

"no difference between the good one and the repaired one" : could you confirm by measuring their respective efficiency ?

[spirou38]

Actually you applied the shim method to center the voice coil with four pieces of plastic of suitable thickness.

"no difference between the good one and the repaired one" : could you confirm by measuring their respective efficiency ?

For checking voice coil centering I checked with stainless steel special blades and the error was less than 5/100 millimeter but more than 1/100 .

Then I made tests playing cd in mono mode with both speakers very close then very distant . Couldn't notice any difference.

For the moment I have not a lot of time for measuring ; in the following weeks perhaps I will have time to move my Tact digital préamp and Earthworks measurement mike to make response curve and efficiency measurements.

[Earl K]

Good new Yesterday I tried to repair the 035Ti.

Pascal, I'm very impressed when someone executes a successful repair such as you have . Good Show !


I was equally as impressed when RobH fixed a 2435h that he dropped ( it's ironic what sticks in my brain , ha ! )

First of all, I took some measurements and found that the diameter difference between the "cylinder" that is centered in the magnet ( called polar part ??? ) and that goes in the hole of the ring ( that was unglued from the magnet ) and the hole of the ring was exactly 1.6 mm.

So I looked after some 0.8 mm non magnetic parts and found some plastic that was exactly 0.8 mm thick. I cut four 16 mm wide parts . Those plastic parts can easyly be bent.

Then I inserted the 4 plastic parts between the magnet and the cylinder inside the magnet, put some cyanoacrylique glue on the magnet ( taking care that there will not be some glue in the centering holes and screw holes of the ring when gluing the ring ), and put the ring that because of the plastic parts automatically centered itself.

Of course I first tried without glue !

I waited 24 hours so that the glue could dry. Then carefully mounted the diaphragm and put the 035Ti in the L80T.

Great sounding, no difference between the good one and the repaired one, no rubbing coil sound . I hope that will last for a long time ...

Thanks for the "schooling" on the method !

,,,,,,snip,,,,,, in the following weeks perhaps I will have time to move my Tact digital préamp and Earthworks measurement mike to make response curve and efficiency measurements.

- At the bottom is the response for one of my 035Ti(s) . This was taken a few months back . It was either 20 or 25 degrees off-axis .

- Previous to these ARTA measurements, just listening to the "crest-factor" of pink noise being run through this tweet led me to the conclusion that it was a nice tweeter .
- My CSD would seem to support that view .



>< cheers

[mech986]

Spirou: Great job on the repair. Excellent engineering of the solution, and certainly a good technique. For your information, the tool you pictured is called a Vernier Caliper and it is very handy to have.

See this reference:
http://en.wikipedia.org/wiki/Caliper


EarlK: That waterfall plot is great. What software and measurement system are you using? Do you have plots which extend the Frequency (X-axis) marking back to the Zero time mark so that it is easier to see where the resonance ripples and troughs are located?

You learn something new here at LH everyday!!

Regards,

Bart