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

[transducergeek]

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.

[scott fitlin]

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!

[John W]

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.

[Mr. Widget]

...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

[Steve Schell]

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.

[scott fitlin]

Send it to JBL!

[John W]

What does JBL typically charge for realigning a driver like the 2420 and how long does it normally take?

[scott fitlin]

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

[yggdrasil]

Labor rates: http://www.jblproservice.com/pdf/Factory%20Labor%20Rates/Misc%20Factor%20Labor%20Rates.pdf

Remagnetize: $27

[mech986]

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

[pelly3s]

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