JBL L112 - Advice on replacing pots.

[scubadude]

Hi, I"m new to the forum. Just wanted to chime in to get some advice on replacing the pots that control the high and mid frequency output on some L112s. There are four screws that secure the assembly/pots to the cabinet. Problem is that they are under the faceplate that is glued to the front of the cabinet. I tried to get a deep socket into the hole to remove the nuts holding the pots but there isn't sufficient room to do so. Only other option I see is to remove the faceplate. My fear is that removing the faceplate will destroy it. It's made of what appears to be aluminum and I suspect it will crinkle during removal and never look right when reapplied. Anybody got any tricks for this? I've put alot of time into getting these speakers mint and fully original and would hate to blow it now. I snagged the pic below off the internet to show the problem area. Thanks in advance.

http://dev.johnfortier.org/video/l112face.jpg

[hjames]

Its called a "Foilcal" (I'm guessing from foil decal).
Prevailing wisdom is that its held in place with a kind of rubber cement - hit it with a blow dryer and fan that back and forth across the foilcal until the glue warms and softens, and you should be able to ease it off the baffleboard intact. That should reveal some countersunk slotted screw that thread into T-nuts (captive nuts) embedded on the Lpad board.

The "pots" are called Lpads ... (perhaps for "level control pads?)

[scubadude]

WOW, now that's what I call service! :bouncy: Thanks for the speedy reply. I'll give the heat trick a try to see how it reacts. This would be great. I will post results when I have them.

[Zilch]

Peeling it will bend it, of course, so I slide a thin blade or spatula underneath as I go, instead....

[scubadude]

Thanks Zilch, I just got back from Sears, got a nice razor scraper for the job. So if all goes as planned I'll be ready to glue the foilcal back on after I replace the L-Pads. What's the best way to do this? Reheat and use the existing glue? Or use new adhesive?

[scubadude]

I guess the next obvious question would be: If new glue is needed what should I use?

[briang]

In keeping with other advice here, peeling will ruin the foilcal. However, as Heather, and Zilch stated, heating and putting something under the foilcal to work it loose works.

With the speaker on it’s back, I used a heat gun (fancy blow drier) and dental floss (lots of it too). I would heat the foilcal to soften the adhesive (looks like a hot melt type to me) and then saw the dental floss back and forth pulling it along (not pulling up) under the foilcal. I broke the floss many times, and my fingers began to hurt. But after about 5 minutes per speaker I was able remove the foilcals from my L96s and L112s in pristine condition. Patience is the key. (I imaging piano wire or wire guitar strings would work too; be careful not to cut yourself).

Once the foilcal is removed, you can remove the four countersunk screws to allow the removal of the L-Pad assembly.

I’ve yet to replace the foilcals (still working on the cabinets), however my plan for reapplication is to use a clothes iron (on high heat) to reactivate the adhesive and press back on the cabinet (maybe with 3M’s blue painters tape to hold it in place). I may use a cotton shirt and/or bakers paper to prevent damaging the screen print on the foilcal.

Good luck and post your results

[scubadude]

Good News! Mucho gracious Señorita and Zilch. The heat did the trick. I used a heat gun but I think a blow dryer would work fine. I used a razor blade to get one corner unstuck then started with a #11 guitar string from there. Zilch's floss trick proved to be a little better due to the abrasiveness of the floss as opposed to the slick finish of the guitar sting. However, I did use the guitar string on a few stubborn spots. The glue sort of balls up so I'm thinking that removing the old and using fresh adhesive would be best. I may try plain old rubber cement to ensure future serviceability. This is a big relief and something I would never have thought to try. So, once again, Thanks.

http://dev.johnfortier.org/video/success.jpg

[Zilch]

HEY! We see those beautiful tweeters and Crown amp back there! :thmbsup:

[Floss was Brian's idea, actually, but I'm not above claiming it was mine, now.... :p ]

[scubadude]

Thanks for correcting me Zilch, in my haste to post I mixed up the names. So here is my official "Thanks Brian". :)
Got some more questions but will start a new thread since the topic is crossovers this time around.