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Thread: Early Jim Lansing label 175 driver throat/phase plug deterioration question

  1. #1
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    Early Jim Lansing label 175 driver throat/phase plug deterioration question

    I have a very early 175 driver with the smooth grey finish and Jim Lansing decal. It seems the pot metal throat and phase plug have cracked and deteriorated in several places, neither are salvageable. The warped phase plug is pushing on the magnet and causing a gap where the diaphragm plate and body meet. I would really like to repair/restore this driver because it is cosmetically mint and a very early version. My questions are, is it possible to replace both the phase plug & throat with later model 175 parts? Is it possible to remove these parts from a later model 175's without damage? And are there any either options, like using parts from a different model or make? Any help is greatly appreciated.

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    Senior Member jcrobso's Avatar
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    No easy way, sorry.

    Quote Originally Posted by AudioDive View Post
    I have a very early 175 driver with the smooth grey finish and Jim Lansing decal. It seems the pot metal throat and phase plug have cracked and deteriorated in several places, neither are salvageable. The warped phase plug is pushing on the magnet and causing a gap where the diaphragm plate and body meet. I would really like to repair/restore this driver because it is cosmetically mint and a very early version. My questions are, is it possible to replace both the phase plug & throat with later model 175 parts? Is it possible to remove these parts from a later model 175's without damage? And are there any either options, like using parts from a different model or make? Any help is greatly appreciated.
    Welcome to the forum!
    Maybe one of our JBL dealers will also post, but it may only be able to be done at JBL.
    The magnet has to be de-energized, the driver can then be taken apart, the throat & plug replace, re-assembled and then re-energized. Cost???
    The parts would have to be JBL parts, only a JBL dealer can answer the other questions.

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    HI, Thank you for your reply. I did call JBL Pro. They said they can't repair it. They were the ones who suggested I try posting on this forum. I am hoping to locate a beat-up 175 that I can cannibalize. I really want to bring this unit back. Thanks again

  4. #4
    Senior Member SMKSoundPro's Avatar
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    Question:
    Can a 2410 be cannabalized to provide the throat?

    I would think an older grey 175 is worth more to the world than a 2410.

    I am just asking.

    Scotty.
    One step above: "Two Tin Cans and a String!"
    Longtime Alaskan Low-Fi Guy - E=MC▓ ▒3db

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    That would be a much more inexpensive option, if they are of the same design. I really want to know if it is even possible to remove the throat without damaging it? Thanks for your help.

  6. #6
    Senior Member Steve Schell's Avatar
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    AudioDive, you have diagnosed the problem correctly. This lousy metal has caused havoc in all sorts of products, like the action support brackets in some grand pianos. The metal deteriorates over time, growing in size and cracking on its surface.

    I have a dozen or so rusty JBL 2420 bodies in my shed. If I ever get around to it these will be converted to field coil operation with new center poles, so I will have no use for the throat inserts. So far these show no signs of the pot metal disease, so they must have used a better alloy. One of these throats has already been used to fix a driver similar to yours, so they do fit. If you send me a PM with your mailing address I will liberate another throat insert and send it to you. Of course you will have to have your driver re-magnetized after it is back together; Orange County Speaker is one source for this work. I am happy to see that you value your early 175 and are willing to go to some trouble to save it.

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