+ Reply to Thread
Results 1 to 11 of 11

Thread: 2420 is misaligned, phase plug off center, or top plate is, how to adjust?...

  1. #1
    Senior Member
    Join Date
    Dec 2004
    Location
    Los Angeles, CA
    Posts
    303

    2420 is misaligned, phase plug off center, or top plate is, how to adjust?...

    I thought I would write to the forum due to your cumulative knowlege about 2420/LE85 drivers and their repair/mantenance procedures as I have read on some thread searches.

    I just purchased a used 2420 and it has a "shifted" or misaligned phase plug, or top plate, I can't tell which.
    Anyway, the diaphram will barely scrape into the gap, it seems that the space is twice the gap as the other side is, so it must be out by what, 5-10 mils? It distorts and I got the 'phram out again, barely.
    Can I re-adjust (center) the gap by any means? Hammering? Loosening? Chanting and Praying? What is the recommended procedure? And then what is the way to do it "unoffically" ... On a budget...

    Thanks, and do you know where I can get a pair of new diaphrams for the two 2420's I now own, (without spending a fortune for outrageous "retail" units) which have no diaphrams now... Thanks, again, Rolf Erickson.

  2. #2
    RIP 2010 scott fitlin's Avatar
    Join Date
    Apr 2003
    Location
    Brooklyn NY
    Posts
    4,657

    Send it to JBL

    realigning the gap or the top plate, that is a job for JBL! Call the factory, get a return auth. # and let them do it, you pay the money, and you get your driver back in proper working order, and you will be happy!
    scottyj

  3. #3
    Senior Member John W's Avatar
    Join Date
    Jun 2004
    Location
    Renton, WA
    Posts
    586
    I agree that sending the driver to JBL is the best way to get it fixed. But, you can remove the diaphragm, hold the driver by the throat and use a rubber mallet to gently center the top plate. The magnetic force is not so strong on these that it can’t be overcome by a few firm taps.

  4. #4
    Administrator Mr. Widget's Avatar
    Join Date
    Apr 2003
    Location
    San Francisco
    Posts
    8,501
    Quote Originally Posted by John W
    ...but, you can remove the diaphragm, hold the driver by the throat and use a rubber mallet to gently center the top plate.
    You can true a damaged car wheel with a rubber mallet too, but I am not going to drive on the freeway with you...

    Infredible had an otherwise beautiful 2420 that sounded and measured out of whack... he bought a single 2420 on eBay with no diaphragm for under $50... OK, it was also painted a lovely brown color... but once we installed his diaphragm in it, it performed flawlessly.

    Just another option...

    Widget

  5. #5
    Senior Member Steve Schell's Avatar
    Join Date
    Jun 2003
    Location
    Long Beach, CA
    Posts
    1,426
    Hi Rolf,

    I just disassembled an old rusty 2420 the other day to have a look inside. A thick aluminum "donut" shaped flat plate is attached to the underside of the top plate with three tiny bolts. This plate's inner diameter tightly grips the center pole, holding it in concentricity with the top plate. The three bolts were surprisingly loose on the one I took apart, allowing possible movement between the center pole and top plate.

    On the Altec drivers I have had apart, there is a thin pressed metal centering ring which is epoxied to the underside of the top plate as well as held in place with three tiny cap screws.

    IMO, your driver needs to come apart so that things can be recentered and the bolts retightened. This recessitates demagnetizing the driver (or a very careful prying operation) and remagnetizing afterward.

  6. #6
    RIP 2010 scott fitlin's Avatar
    Join Date
    Apr 2003
    Location
    Brooklyn NY
    Posts
    4,657

    Ill say it again!

    Send it to JBL!
    scottyj

  7. #7
    Senior Member John W's Avatar
    Join Date
    Jun 2004
    Location
    Renton, WA
    Posts
    586
    What does JBL typically charge for realigning a driver like the 2420 and how long does it normally take?

  8. #8
    RIP 2010 scott fitlin's Avatar
    Join Date
    Apr 2003
    Location
    Brooklyn NY
    Posts
    4,657

    Call them!

    1-800-8JBL-PRO call and ask how long and around how much it costs!
    scottyj

  9. #9
    Super Moderator yggdrasil's Avatar
    Join Date
    Dec 2004
    Location
    Bodø, Norway
    Posts
    1,128
    Johnny Haugen Sørgård

  10. #10
    Senior Member
    Join Date
    Aug 2003
    Location
    La Habra, California USA
    Posts
    1,165
    Hi Rolf,

    I spoke to Dave at JBL PRO parts recently and he mentioned that their lab/repair shop can remag / recenter, re-install the diagphragm and test with no problem. Takes usually about 2 days once inspected and estimate ok'ed by you for the work. Costs you should discuss with them for the specific work you want done. Dave assured me that there are some very dedicated folks down there who take pride in re-invigorating any drivers which are sent to them.

    Also, OC Speaker Repair can also do the same work as they also have a magnetizer in their shop (one of very few I understand). They are JBL Authorized Service station as well, for what that is worth, and they generally have done very good work for me and many others.

    Good luck on getting your driver repaired.

    Regards,

    Bart

  11. #11
    Senior Member pelly3s's Avatar
    Join Date
    Nov 2004
    Location
    Springfield MA
    Posts
    650
    I have one of those scarey machines too. The guys down at JBL are great with it. I would say send it out to my shop but since you live in CA you might as well send it right to JBL or OC. Good luck with it

+ Reply to Thread

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Similar Threads

  1. 2220a Top Plate Thickness ?
    By Earl K in forum Lansing Product Technical Help
    Replies: 0
    Last Post: 05-02-2003, 10:14 AM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts