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View Full Version : Speaker basket terminals loose on old JBL?



Flodstroem
01-18-2017, 12:18 PM
Hi folks

When checking an old 2108A I found out it sounded like it was filled with sand or gravel :blink:
OK, this one has to be re-coned so I put it aside.

Then a year later when trying to repair a 112A cone from old tape and loose paper from the cone I discovered
that one of the drivers terminal was loose. I found out that a screw bit PH-2G was a perfect fit for that screw and tightened it.
Suddenly I remembered the 2108 that sounded so bad and also had a bad DCR reading. When checking the screws on the 2108
I found out that both screws was loose and I tighten them the same way as I had done with the 112A. Then, when the 112A was Ok and was checked on the generator I also checked the 2108 and to my surprise it sounded good, it sounded the same as for the 112A. Wow! both speakers ready for a re-foaming.

Though I have some older JBL speaker in stock I took out every one that was not Ok, some was classified for re-coning others for re-foaming.
I found two LE8T that was bad. Also I found two LE15A that had bad DCR readings (11.6 ohm and the other between 9-15 ohms). Al screws was loose on the Le8 and on the LE15. After tightening al screws the DCR was 5.2 and 5.3 on the LE8Ts and 7.6 and 7.8 for the LE15. After checking them on the generator + a test with music my conclusion was they are alright speakers ready for a re-foaming.

Now whats this al about? Well my first conclusion was that those all speakers had to be re-coned but the fault was the loose terminals: All JBL old speaker/basket terminals are isolated from shorts with plastic (fiber?) )washers, one at each side of the chassis. Speaker connection cables coming from the voice coil is soldered on a ring terminal and the ring terminal are screwed to the basket terminal. After a long time in duty those two plastic washers do crimp probably by ageing or material fatigue (or heat?) and screws come loose. There is also a risk for corrosion on those loose plated screws.

It was a little bit tricky to try to tightening the screws on the LE15 because it was a tight area just behind the cones. I used a screw bit no PH-2G for all screws that I tightened. For the LE15 I had to put the bit in a wrench and secure the bit with heavy tape for to do the job........

The picture shows the plastic washers and where the screws are located. Hope this notes could prevent some of you for to do an unnecessary re-coning :D
75485

FE3T
01-21-2017, 03:44 PM
I have a confession to make.

Every single time I recone a older JBL driver with the nickel plated push terminals. I replace them with Gold plated terminals that take larger wires and use a locking washer below the nut that hold the terminal to the basket.
75566


Ps do you happen to have a pair of LE8T-H baskets? that would be the ones with terminal brackets BETWIN the basket spokes.

Flodstroem
01-21-2017, 05:33 PM
Ps do you happen to have a pair of LE8T-H baskets? that would be the ones with terminal brackets BETWIN the basket spokes.

No baskets though, butt full operational LE8T-H :D But......... I have the Alnico version baskets LE8T ;)
Btw, are you working as a pro with JBL in Norway?

Aaron
01-22-2017, 05:20 PM
A very worthwhile finding that will no doubt save some speakers from the scrap heap. :thmbsup:

Something to add: If you snug up the terminals and you still have problems, the tinsel leads aren't made entirely of metal so they might appear intact & in one piece and still fail to make a connection. Replacing them requires a steady hand and some fine scale modeling tools but at least it doesn't mean hunting for expensive NLA recone kits.

Thanks again!

FE3T
01-22-2017, 06:31 PM
No baskets though, butt full operational LE8T-H :D But......... I have the Alnico version baskets LE8T ;)
Btw, are you working as a pro with JBL in Norway?

To bad, I would love to get my hands on LE8T basket with the terminals BETWIN the basket spokes instead of on top of one of them

Nope. just a happy amateur without any special connections. Works at a sawmill for a living (graveyard shift this week, that's why I am still up)

Lydrommet AS and Per Kjemo are the man to contact when servicing and service parts for JBL Pro in Norway are needed.

.

Flodstroem
01-23-2017, 09:38 AM
To bad, I would love to get my hands on LE8T basket with the terminals BETWIN the basket spokes instead of on top of one of them

Nope. just a happy amateur without any special connections. Works at a sawmill for a living (graveyard shift this week, that's why I am still up)

Lydrommet AS and Per Kjemo are the man to contact when servicing and service parts for JBL Pro in Norway are needed.

.

OK, thanks.
Whats the special demands for that you want the terminals BETWIN the basket spokes? Esthetic purpose?
Im an old JBL pro service man from Sweden but works with JBL only as a private nowadays.................. :D

Thanks to you Aaron for your comments regarding the tinsel leads and that they aren't made entirely of metal. Im aware of that but have never had the experience with opened circuits do to that issue......... ;)

FE3T
01-23-2017, 07:26 PM
OK, thanks.
Whats the special demands for that you want the terminals BETWIN the basket spokes? Esthetic purpose?

Because I want to use it with a 3" ferrite motor and only this placement of the terminals leave room for that. . and i suspect that this version of the basket already have the markings for the 3 bolt 3" ferrites i have here. Basically create something as close to a 2108H as accessible parts allow.

Flodstroem
01-24-2017, 03:37 PM
OK, I see. When looking at my LE8T-H there is nothing that indicating a 3 bolt pattern. But its impossible to see anything under the spider tough. Also, the top plate on the LE8T-Hś magnet is recessed in the basket. But its possible JBL used the LE8T-Hś basket for their 2108A/H and 112A/H......
Im going to take a look at my single 2108 tomorrow.

FE3T
01-24-2017, 04:08 PM
OK, I see. When looking at my LE8T-H there is nothing that indicating a 3 bolt pattern. But its impossible to see anything under the spider tough. Also, the top plate on the LE8T-Hś magnet is recessed in the basket. But its possible JBL used the LE8T-Hś basket for their 2108A/H and 112A/H......
Im going to take a look at my single 2108 tomorrow.

If you look at the pic in this post: http://www.audioheritage.org/vbulletin/showthread.php?37609-Crazy-2108-4-quot-question&p=400347&viewfull=1#post400347 You se 3 recesses in addition to the 4 bolts that hold the magnet to the basket
I belive that if you drill trough the basket in the center of these recesses, you end up with a bolt pattern that matches the 3 bolt version used on some of the 3" ferrite magnets.

I have also seen the same on a LE14A basket, it has 4 recessions that looks to match the bolt circle on a 3" Alnico motor, but I have never seen a 3" coiled LE14 or understand why anyone would want one above the 4" coiled one. :blink:

I believe the LE8T-H basket are cast identical to the 2108/112 baskets, but machined differently after casting.