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JBL Dog
09-14-2003, 11:31 PM
I was tweeking the 4343's tonight and noticed I have some L-pads that aren't functioning properly. One was damaged years ago (the "pot" was pushed in). The contact points sound like they're on full at all times on the 2420, which can be overwhelming.

If I'm going to replace one, I might as well replace all of them.

Has anyone ever done this?

How much of a pain in the a$$ is it to remove the foical (ID tag or whatever it's called) without causing damage?

Are original L-pads still available at JBL?

Thanks in advance!

This message comes from JBL Dog :band:

IDF
09-15-2003, 02:00 AM
Hi Dog,

I have had to replace the 2121 L-Pads a few years ago.
It is a very simple operation if you take care to note where each coloured wire goes to.
The safer way to take off the foicals is to heat them with a hair-dryer.

Hope this helps
Phil
:)

4313B
09-15-2003, 06:02 AM
I've posted the L-Pads before but here it goes again:

Standard L-Pad is 10285 - don't even waste your time
High power 8 ohm L-Pad is 58450 - use in place of 10285
High power 16 ohm L-Pad is 51594

IDF is right, hair dryer, heat gun, etc.
That's what's printed in the service manual.

You should be able to get the same L-Pads from Parts Express for a bit less.

rgrjit8
09-19-2003, 03:50 AM
Okay some clarification here please.

I'm having problems with my 2441. I've eliminated the driver itself, which leaves the L-pad or the crossover. I hear no scratchiness in the L-pad when I turn the pot.
I removed 2 screws but it still won't come out. Are there more screws under the label?
Is this what you mean by foical?
Damn. I hate to ruin that on my 4355.:banghead:

Somebody hold my hand will ya?

boputnam
09-19-2003, 08:17 AM
Originally posted by rgrjit8
I'm having problems with my 2441.
Is this what you mean by foilcal?
Give some more descriptions of what is the "problems", when they started, etc.

What's wrong with the foilcal?

Maybe this all will help the helping.

rgrjit8
09-19-2003, 03:01 PM
The sound was cutting out. A quick jolt of volume would bring the sound back. It has been getting progressively worse.
I had the same thing happen to my L-166s way back when. The problem was the L-pad, but you could hear scratchiness as you turned the control.
In the present case, there is no scratchiness which makes me fear that it is something in the crossover itself rather than merely in the L-pad.
The driver is good. I swapped it out with an 093 mid from one of my XPLs and got no sound. Then I connected the 2441 to the slot radiator(2405) output at low volume of course, and got fine sound.
So like I say, it's crossover or L-pad.

But the L-pad isn't coming out by removing two screws. I fear there may be two more screws countersunk in the baffle under the aluminum id plate. I really don't want to damage this.

boputnam
09-19-2003, 03:29 PM
Originally posted by rgrjit8
But the L-pad isn't coming out by removing two screws. I fear there may be two more screws countersunk in the baffle under the aluminum id plate. I really don't want to damage this. Most are exactly that way. I've been able to skinny a putty knife under/around these plates but it can then take some pressing to get it as flat as before.

JBL Dog
09-19-2003, 04:05 PM
There's definitely screws under the foilcal. When I had to have a crossover worked on in the 4343's, I took then entire front baffle plate (minus drivers) into the repair shop. The tech looked at me like I was nuts!

:screwy:

"Do you want the work, or not!"

I am going to "very carefully" remove the foilcal so I can work on the L-pads. Drivers are fine!

:yes:

This message comes from JBL Dog :band:

rgrjit8
09-19-2003, 07:49 PM
Okay, I'll do it. I see no recourse. Even if the L-pad is not the problem, I'm still going to have to take it out to have someone work on the crossover.
But it still bums me out. My wife will be pissed too. (Any ugliness will affect resale value) Why did JBL design them this way?

I'll be back.

JBL Dog
09-19-2003, 09:12 PM
Originally posted by rgrjit8
Why did JBL design them this way?



Just like everything else, they want to make it difficult for the end user to do their own repairs. Besides, to be a certified JBL Tech, the final course you had to take was Foilcal Removal 101. I think I'll practice on Audiobeer's L300's. :D

I'll tackle that when the kids are out of the house and I can cuss like a sailor!

:banghead:

This message comes from JBL Dog :band:

rgrjit8
09-19-2003, 09:42 PM
Good one Dog, I wish I could laugh.

I think I did a fair job on the foilcal but I can tell right now that it's never going to be the same. I also managed to nick some of the blue paint off the baffle with my wood chisel.:biting:

And, worst of all, I've eliminated the L-pad as the culprit. I powered things up and made a jumper between the contacts on the pot and got no sound from any combination. This means the problem is in the crossover itself.:banghead:

So now what? Do it right and take out both crossovers, and replace all caps?
Trust one of the locals to do the work, or send them back to the US?:bomb:

Or, do I make the wife happy and just go for the quick fix on one side?:slink:

I'm open to suggestions. There's a factory authorized JBL service center here but they don't inspire much confidence. At first they tried to tell me that there was no such model as the 4355, then the whined and complained about how old it was, no parts etc.

Can anyone put me in contact with a reliable guy who would rebuild both crossovers competently at a reasonable price?:help:

boputnam
09-20-2003, 08:08 AM
Originally posted by rgrjit8
I also managed to nick some of the blue paint off the baffle with my wood chisel.:biting:

Uh-oh... That's the worst of all! :rotfl:

The schematics for the 3155 can be found here (search for "3155 schematic"), or at the JBL website, if they're of any help.

Unless somebody here chips-up, I think if I was in Seoul I'd email of phone JBL Pro and get their advice. They, at least, know what a 3155 is!

You might post a plea in Marketplace to help spread the word.

boputnam
09-20-2003, 08:30 AM
Originally posted by rgrjit8
I powered things up and made a jumper between the contacts on the pot and got no sound from any combination. This means the problem is in the crossover itself. and

Then I connected the 2441 to the slot radiator(2405) output at low volume of course, and got fine sound.

Would make me wanna tear into that crossover myself. You've pretty much isolated the problem - I think - to the 2441 circuit. The networks are easy to remove (now that you've got the L-pad out ;) ), so maybe you can trace the MF circuit, get out the multi-meter and post your findings.

Are you handy with a soldering iron?

rgrjit8
09-20-2003, 10:21 AM
Soldering.
Well, I passed the Marine ground radio repair course, but was then sent to a low echelon shop where the only repairs we did was replacing modular components which were in turn sent on to high echelon shops for further diagnosis.
So that brief introduction to soldering 25 years ago is all I"ve had. I'd hate to use "my baby" to try to brush up my skills.

I've had my wife looking for my cheap little multimeter all week. I'm beginning to think it might still be back in the states.

I'll make some more calls on Monday, there's got to be somebody here who is familiar with what I've got.

rgrjit8
09-20-2003, 11:29 PM
Well the crossover is out. It looks pretty easy to work on. I'm tempted to just go ahead and replace all ten caps myself and see if that doesn't somehow "accidentally" fix it.

I see nothing burned, leaking or loose so are the odds not in my favor that it is an open cap?

************************************************

Oh, now I get it!

aluminum foil + decal = foilcal

Now I know why no one ever told me, "Don't run with that sharp mind! You might fall and cut yourself!"

- I don't HAVE ONE.

boputnam
09-21-2003, 12:08 AM
Originally posted by rgrjit8
Well, I passed the Marine ground radio repair course... Ha! That is already coming in handy!

But the rest of your post has me :rotfl:

lpd
09-21-2003, 01:34 AM
Just a reminder for l-pad needy folks..antique electronic supply is clearing out 8 and 16 ohm l-pads for cheap!! They appear to be of decent quality. I'll look up the part # later for those interested.

Tom Loizeaux
09-21-2003, 11:03 AM
Before removing foilcal, it may be a good idea to buy a replacement L-pad and wire it in from behind the baffle by switching over the wires from inside. If that solves the problem, then proceed with the replacement, if it it doesn't, you can look further without unnecessarily tearing at your foilcal!
I suspect it IS the L-pad though.

Tom

GordonW
09-21-2003, 11:16 AM
Originally posted by rgrjit8
Well the crossover is out. It looks pretty easy to work on. I'm tempted to just go ahead and replace all ten caps myself and see if that doesn't somehow "accidentally" fix it.

I see nothing burned, leaking or loose so are the odds not in my favor that it is an open cap?

Try using a short wire, and jumping across the in-line caps in the midrange circuit (JUST the ones in series with the signal, NOT the ones connected to ground), with the driver attached, and a source at low volume. You should be able to tell, pretty much immediately, if a cap is open... jump a bad one, and you should get sound from the mid...



************************************************

Oh, now I get it!

aluminum foil + decal = foilcal

Now I know why no one ever told me, "Don't run with that sharp mind! You might fall and cut yourself!"

- I don't HAVE ONE.

ROTFL :rotfl: :rotfl: "Hey, watch out, you're gonna put an eye out with that thing!!" Man, don't sweat it, even the best of us do a "DUH" once in a while... :o :D

Regards,
Gordon.

rgrjit8
09-23-2003, 12:55 AM
Well it appears that I've violated the First Rule of Electronics:
KISS Keep It Simple, Stupid!

My wife took the crossover to the JBL service center. They said there was nothing wrong and that it must be a bad diaphragm in in the 2441. :banghead:

I rechecked the driver. It worked fine as I'd already determined.:biting:

Then the wife mentioned how the tech had wiggled and pressed down all the spade contacts on the crossover wires before he'd run his tests.

I put everything back together and it has been working fine for several hours now with now cutouts.
It must have been a simple LOOSE CONTACT with a wire!:die:

Well at least it didn't cost me anything and I now have the 4355s in mirror image configuration.:rockon2:

It's a drag about the foilcal though. (insert icon showing tears)

GordonW
09-23-2003, 09:57 PM
Ah, that's Rule One of Fixing Stuff that Don't Work:

1) If it don't work and you can't find anything obviously wrong, take it apart, and put it back together again. It'll probably work afterwards. :D :D :D :D

Regards,
Gordon.
been there, done that... more times than I can count!!