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Thread: How to ruin your day.

  1. #16
    Administrator Robh3606's Avatar
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    Hello Zilch

    Your right about that. Same for the 2431's. The 2 I just got were in good shape overall however the one I dropped had the diaphram in backwards and I didn't see this until after I got the cover off. It also has a small crease in the diaphram that I certainly didn't put there but I couldn't very well go back to the seller and complain after I dropped it. Point is it was not "New" as advertised but for these prices how can you complain for what you are getting???

    On another note EUREKA!!!! It worked I know have a working pair again. I would like to thank you all for your encouragement and ideas all around we should pat our collective selves on the back because we now have a viable repair if anyone else has a whoops with one of these. I tried an epoxy, got the shim out and just watched the top plate creep over to the pole in slow motion. I took a chance and used medium viscosity super glue. It worked like a charm. One thing however, I should have done a better job shimming. I depended on the material thickness and diameter of the shim to help hold the top plate. It didn't work it somehow found the thinnest part to creep towards. I am off -.005 on one side so I am under spec on the gap size over a small portion of the gap. The coil still is free and there actually is quite a bit of room in that gap otherwise I would be toast with that much offset. Really won't know if this worked until I measure the driver. But it sure looks OK for now. The glue is holding.

    Hello norealtalent

    That is a great idea to use a 2431 core and I had to laugh when I read it cause I didn't even think of it. I was hell bent on getting it fixed and thanks to you guys we did.

    I found Ferro Fluid on E-Bay to recharge the driver.

    Rob
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  2. #17
    Senior Member edgewound's Avatar
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    Congrats Rob....hope it works well.

    Zilch...

    The source I got my (4) 2435's and (2)2407's from said they came from new Vertec systems that were part of a big nightclub or sound company operation liquidation. Seller was very accomodating to me and offered me more drivers too through e-mail but lacked the funds for more at the time.
    He even delivered to my shop ...nice hispanic guy...had wife and young kids with him in a nice new SUV.
    Edgewound...JBL Pro Authorized...since 1988
    Upland Loudspeaker Service, Upland, CA

  3. #18
    Senior Member grumpy's Avatar
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    Talking

    Glad to hear this story had a happy ending.

    Prompted me to check mine over and have a listen.
    Ferro-fluid present, no creases. I don't have any horns
    designed for these (yet), but they should make for some
    interesting experimenting



    -grumpy

  4. #19
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    As an alternative to the shims, it would seem that one could wrap the piece with Teflon tape to fill the gap. When the glue dries, the tape could simply be unwound. And the glue won't stick to it.

  5. #20
    Administrator Robh3606's Avatar
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    As an alternative to the shims, it would seem that one could wrap the piece with Teflon tape to fill the gap. When the glue dries, the tape could simply be unwound. And the glue won't stick to it.
    Hello toddalin

    I not to sure that would work. We use teflon at work and one issue it has is cold flow. If you compress it it won't hold it's shape. It's simply too soft. You can only lower the top plate back down in a controlled manner with the screws. The closer you get to the the magnet the more the sideways force towards the pole piece increases. You need a shim that can hold up against this sideways force until you get it all the way down and the glue sets. Those magnets are really powerful. I had a razorblade get grabbed from 6 inches away from under a piece of paper as I put it down on my desk. That scarred me!! I was very lucky I wasn't in the path. It could have done some serious damage to my fingers. If they can't demag them to work on them I can understand why JBL won't fix them. They are an accident waiting to happen when the magnets are fully charged.

    Rob

  6. #21
    Senior Member edgewound's Avatar
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    Quote Originally Posted by toddalin
    As an alternative to the shims, it would seem that one could wrap the piece with Teflon tape to fill the gap. When the glue dries, the tape could simply be unwound. And the glue won't stick to it.
    Teflon tape would most likely be way too soft...and how are you going to measure how many layers to build up to make the right gap shim thickness?

    The shim stock needs to be strong enough to not crush under the force of the pole piece attracting the top plate to it.

    You're welcome to experiment and show us your results though....maybe I'll learn a new process.

    You CANNOT under estimate the pull force going on here....it's extreme!!!

    You can hurt your self BIG TIME if you're careless and think this is no big deal.
    Edgewound...JBL Pro Authorized...since 1988
    Upland Loudspeaker Service, Upland, CA

  7. #22
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    Quote Originally Posted by edgewound
    You can hurt your self BIG TIME if you're careless and think this is no big deal.
    And that'll really "Ruin your Day"!

    Congrats Rob!

  8. #23
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    suppliers such as enco and msc sell shim stock in all manner of sizes ,materials ,and thicknesses.

  9. #24
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    Hi

    What a great thread !

    Rob, I'm glad you fixed your broken 2435 .
    I'm sure the support from the others who weighed in with their thoughts and advice, helped you find a workable solution .

    Re; Ferrofluid .

    - What did you find ? The stuff comes in many weights / which effects the HF response through coil dampening .
    - I'd CLIO the driver before adding anything into the gap. That way you can document the results.
    - FWIW ; the last time I checked , Meyers Sound Labs ran ferrofluid in the gap of the compression drivers for their SR products. They ran a dry gap in the same drivers when used in their large studio monitor .


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