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View Full Version : JBL L220 Oracle back crossover panel removal



script56
11-12-2014, 04:22 PM
63581Ive seen many posts on the L220 speaker system, but I read nothing on how to remove the back panel after it still being stuck with screws removed. I believe it was glued shut along with screws. Any ideas how to remove back without damaging wood? The particle board on the outer cabinet is pretty thin around that area, so prying on the wood is not a good idea.

hjames
11-12-2014, 07:47 PM
Loosen and remove all the screws. lay the speaker on its back on the floor.
Get a length of 2x4 approx the width of the cabinet. Lay it on the floor, then lay a towel across it.
Lift the top of the cabinet a foot or so off the floor, slide the towel covered 2x4 underneath the cabinet
just below the bottom of the removeable panel. Drop the cabinet so it falls on the 2x4.
Rinse and repeat until the upper panel falls off the back.
If you need to, you can lift more than 12 inches, but I would not go too far a fall.

The alternative would be to use a slide hammer like is used in auto-body work.
Screw the end of the tool into one of the holes near the center of the removeable panel,
and and slide the weight out from the panel and slamming the weight against the stop.

I would prefer using the calibrated drops against the 2x4.


63581Ive seen many posts on the L220 speaker system, but I read nothing on how to remove the back panel after it still being stuck with screws removed. I believe it was glued shut along with screws. Any ideas how to remove back without damaging wood? The particle board on the outer cabinet is pretty thin around that area, so prying on the wood is not a good idea.

script56
11-13-2014, 10:46 AM
I used a homemade variation of a slide hammer. I know you all are going to hate me for using it, but it was almost perfect and sitting right in front of me. I used a 4343 support bar for the slide hammer. It must be used on inside screws that hold xover board to back panel. It worked very good. The reason I removed was low output of 076. Any guess if it's the cardboard tube that are bad or the 20 ohm 10% caps that are bad?

JeffW
11-13-2014, 10:54 AM
I'd go for door #3, the tweeter L-Pad. Assuming the tweeter is functioning properly.

script56
11-13-2014, 11:22 AM
That was my first thought as well door number three but the L pad works it is not scratchy but the volume when adjusted stays the same low-level. I do have a load from 4411 spare to replace if necessary.

audiomagnate
11-13-2014, 12:10 PM
That was my first thought as well door number three but the L pad works it is not scratchy but the volume when adjusted stays the same low-level. I do have a load from 4411 spare to replace if necessary.

Then it's the series cap. Sometimes after they fail they they will still leak a tiny bit of signal.

script56
11-13-2014, 12:46 PM
I'll check out the schematic to find series cap.

script56
11-13-2014, 02:18 PM
Is the series cap the ones in cardboard tubes or the 20ohm 10%?

Also it looks like one of the roofers has been reconed with authentic Jbl cones. They just do not match because one of the dust caps is darker. If anyone has one available let me know

script56
11-15-2014, 03:03 PM
63596For members future information on disassembling the back panel I have decided to give detailed instructions on a second method of removing the back panel. The second cabinet was even harder than the first to remove the back panel. After trying the slide hammer method and it did not work I decided to go a different route.

what I did, and this is a much easier method, is remove the four screws on the inside of the back panel that hold the crossover board onto the back panel. After removal use a rubber mallet to lightly hammer the crossover board off of the back panel into cabinet. It is okay for it to fall because there is a floor Inside so it can only fall about an inch. After the crossover board is removed laid the speaker cabinet facedown on the floor. Remove 10 screws holding back panel on. Using a normal metal Hammer lightly from the inside, tap the back panel from the cabinet. You have to do this on the middle section of the back panel to avoid hammering where the outside screws of the back panel connect to the cabinet.

audiomagnate
11-16-2014, 07:26 AM
Is the series cap the ones in cardboard tubes or the 20ohm 10%?

Also it looks like one of the roofers has been reconed with authentic Jbl cones. They just do not match because one of the dust caps is darker. If anyone has one available let me know

It's the small yellow capacitor labeled "2.0 UF." An easy test if you don't have test gear is to jump it with a VERY low level signal applied to the speaker's main input terminals. If the 077 level jumps right back up with the jumper wire in place the cap is bad. You should replace the one in the other speaker with an identical cap if it is indeed bad.

script56
11-16-2014, 10:59 AM
Not sure how to do the jumper wire, but I'll look it up. Will these caps work for replacment?

martin2395
11-16-2014, 02:11 PM
The color difference between dustcaps could've been caused by exposure to sunlight for an extended period of time.

script56
11-16-2014, 09:04 PM
I Didn't find much online about using a jumper wire.

audiomagnate
11-17-2014, 03:34 PM
I Didn't find much online about using a jumper wire.

You are just bypassing the suspect cap with a piece of wire, it's not exactly a project worthy of internet research! If the cap is bad you will hear the signal come back into the tweeter, if the cap is good you just get a little more mid with the jumper in place. It takes less time to do it than to describe it.

hjames
11-17-2014, 03:52 PM
I Didn't find much online about using a jumper wire.
Go to Radio Shack and buy some of those Alligator clip jumper wires.
Its just a short length of wire with an alligator clip on each end. Simple!
Easy to use, belongs on every troubleshooter's Toolkit!

script56
11-20-2014, 02:15 PM
Any explanation of how to actually jump with the clips would be appreciated. I have clips and cap, but don't know what do do with them.

hjames
11-20-2014, 02:25 PM
Any explanation of how to actually jump with the clips would be appreciated.
I have clips and cap, but don't know what do do with them.

If you want to bypass a cap, its a kind of colored tube with a wire lead out of each end usually.
You have a piece of insulated wire with an alligator clip on each end.
You would grab the wire lead on one end of the capacitor with one of the clips
and hook the other clip to the wire lead on the other end of the cap.
The electricity will flow through the wire instead of the capacitor,
so you can hear if the cap has failed in some way.

I hope I am not misunderstanding or being too simplistic - I mean no insult.

script56
11-20-2014, 05:19 PM
no you explained it perfect. Thats what I had pictured in my head, I just didnt quite understand that it would block the current like that. Thanks a lot! Also, if its bad, is the 2uf cap for around $18 on parts express about right price?

hjames
11-21-2014, 03:47 AM
no you explained it perfect. Thats what I had pictured in my head, I just didn't quite understand that it would block the current like that. Thanks a lot!

It won't "block" it, the straight wire with clips is a direct short,
so technically you would say it will bypass the cap.



Also, if its bad, is the 2uf cap for around $18 on parts express about right price?

Probably, but what voltage is the cap rated for?
If there is a rating, be sure to match it ...

ama
12-22-2014, 03:45 AM
Hi
Anyone knows how to remove the 4344's back panel? I did removed all the screws on the back panel & the woofer and try to hammer the back panel off from the woofer opening, but the back panel didnt even budged.

script56
12-22-2014, 03:09 PM
I used a car jack to remove front panel of 4343. The 4344 back panel could be removed same way probably but maybe lay cabinet on its side since you won't be able to access inside when laying cab face down.