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Thread: Overcoming foilcal-a-phobia

  1. #1
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    Overcoming foilcal-a-phobia

    I overcame the foilcal-a-phobia last night and removed the foilcals from the L-150's I sold to my roomie. The mids weren't even coming on until you had the L-pad cranked all the way down and forget the highs unless you twitched it just right. I so not wanted to touch the foilcals that I almost wanted to drilled a few holes in the back of the cabs and mount another pair of L-pads in the rear.

    But on Sunday, I visited Steve Gonzalez in sunny Bakersfield and he told me how to remove them perfectly. The trick is to get a super flexible 1" putty blade (I paid over $5 for the Warner Pro at Lowes) and of course the hair dryer. Man, I had those things off in ten minutes. I have three extra sets of L-pads and after getting the ones out of the L-150's, I noticed that the mounting scheme is totally different, with the two clunky "Noble" brand pots mounted on fibreboard and three screws in a triangle formation to hold them in. Ohming out the "Noble" brand, I could see there was problems, especially ohming it out. While turning the knobs, the resistance was jumping all over the place. I tried popping the backs off (something I picked up here on a Singapore 43xx post) and cleaned it but good. But it still sounded like crap, so I replaced both L-pads on the fibreboard with thinner profile pots off've an L-112 unit (I cleaned this one before and ohmed it out with two others to verify that they're all on the same page).

    Ever since I mounted the x-overs permanently to the backs of the cabs and used the in-cab crossover instead of the L-112 unit I had laying off to the side on the bottom, the sound quality had deteriorated. It sounded muddy and lacked midrange strength, because the woofer was really the only thing working well and it covers the lower part of the mids (but not the upper of course). After my switch on the one speaker last night, I was amazed at what it sounded like. The mids are back sweet and strong and you get no dropping out when you turn the knobs. Even the highs are bettah! I am now going to fix my bud's and my little brothers L-150's as well as my L-300's now that I've over come the foil-cail-a-phobia. The only pain in the behind will be to remove the old adhesive from both surfaces before using 3M Spray adhesive on the back of the foil-cal.

    Thanks Steve for your help! (his four L-220/L-222 set up sounds pretty friggin' radical!)

  2. #2
    Senior Member pmakres1's Avatar
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    Excellent tip

    Regis,

    Two comments here:

    1. Congratulations on your success!!

    2. Steve is the man!!


    Best regards always,

    Peter

  3. #3
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    That would be Steve Magalnick - Foilcal Removal / Replacement Procedure. I guess it got lost with a previous version of the forum. :dont-know The proper procedure was published in direct response to the wanton practice of ripping perfectly good foilcals off the loudspeakers, tossing them in the trash and then requesting new ones. Stock was completely depleted and JBL wasn't inclined to run more. In any case, you guys got the gist of it. Many of the Service Centers couldn't grasp the concept.

    decal

  4. #4
    Senior Member LE15-Thumper's Avatar
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    What part of this job requires removal of the foilcals ? I have never owned 150's. Are there hidden screws behind the Foilcals ? Are we talking about the drivers themselves or the Networks ? I remember the 240X series having screws behind the foilcals, is this the subject ?
    LE15-Thumper
    "Give me JBL, or give me death"

  5. #5
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    Replacing L-Pads in various models. The screws were secretly hidden behind the foilcals. Some models had the whole crossover network mounted behind the foilcals. Splendidly BRILLIANT!
    Attached Images Attached Images  

  6. #6
    Senior Member pmakres1's Avatar
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    Hidden screws

    As I recall from many moons ago, my L100's had at least one network screw hidden under the foilcal. Fortunately, I never had need to access it.

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    Da' job

    Quote Originally Posted by LE15-Thumper
    What part of this job requires removal of the foilcals ? I have never owned 150's. Are there hidden screws behind the Foilcals ? Are we talking about the drivers themselves or the Networks ? I remeber the 240X series having screws behind the foilcals, is this the subject ?
    The foilcal removal on many of the vintage JBL products was simply to get to the 'hidden screws' on the L-pads or adjustment pots for servicing or removal. The tricky part was getting them off without damage as Giskard so eleqountly attributed to the original 'Steve' (Magalnick).

    If any of you have any kind of noise or dropout when you rotate the two adjustment knobs for brilliance or presence, then you've got to pull the board with the pots so you can clean them by pulling the round metal covers off've the pots themselves. The pads are electrically part of the circuit and your input signal is feeding through them. Dirty, corroded pots will affect the sound by changing the resistance, giving you degradation of sound. You might be able to clean them inside the cabs, but it sure is tricky getting the little red tube in the vent holes (didn't work for me). Better to have them open and douche em' good!

    Also ohm them out and make sure the resistance between the three terminals on each one is 'even' across the whole range and not jumping around going extremely high resistance for a moment, then dropping to infinity then coming back to normal again. Compare a couple of pots together. If memory from last night serves me correctly, there are three wires on each pot. Between the two outer wires, the resistance ranges from 8 ohms or so, to 35-37 and then goes way out at the last push. Between the outer and inner terminals, it ranges from 0 ohms to 8 ohms. Both mid and hi pots should behave exactly the same on two pot systems. Don't have any knowledge of the bigger ones with three pots, so I won't guess here. Dirty pots will make your speakers sound like crap! Once you clean em' you can adjust the brilliance and presence smoothly and hear just what it's supposed to do effortlessly with no problems

  8. #8
    Senior Member LE15-Thumper's Avatar
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    Quote Originally Posted by Giskard
    Replacing L-Pads in various models. The screws were secretly hidden behind the foilcals. Some models had the whole crossover network mounted behind the foilcals. Splendidly BRILLIANT!
    Ah !!! Ok, the old front mounted L-pads. Gotcha
    LE15-Thumper
    "Give me JBL, or give me death"

  9. #9
    Steve Gonzales
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    Cool

    I'm glad that the tip helped you out Regis. I had/have never seen that post Giskard pointed out. I just used my BRAIN and some common sense to figure out the problem. I'm a bit un-easy when someone says "You're the man", not that I don't appreciate what it means, I have just always enjoyed helping in a positive light and the reward is in seeing someone else benefit from what I've learned. Regis, you're one cool Cat!.

  10. #10
    Senior Member bigstereo's Avatar
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    Does that reading apply to all L pad pots?

    Will those ohm meter readings apply to the pots on the 4311's also?

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    Sure why not???

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    Senior Member Michael Smith's Avatar
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    Removal of Foil Cals

    Hi Guys
    The hair dryer/ heat gun has always been the way to go, I have another wee tip for you'll ,get two pieces of glass 8mm thick and when you remove the foil cal place it on the glass while the glue is still hot then put the other piece of glass on top of it.Then with a weight( speaker magnet is what I use) place it on top to flatten it.
    When you have completed your repair, re heat the foil cal and put back on the box using the glass and weight again and it will look brand new (some times you may have to use alittle more heat depending how much glue has remained on the speaker box)
    Have fun
    Regards
    Michael

  13. #13
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    Is there anyway to reduce or remove scratchiness from the presence and brilliance controls on L100 Century L Pads, without going to the trouble of removing the foilcals?

    Thanks!!
    Barry

  14. #14
    Member Izzy Weird's Avatar
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    My name is Izzy, and I'm a foilcal-o-phobe.

    I finally had to join a foilcal self-help group. In 1972 my 4310s arrived with wiring errors. That’s right, JBL quality control failed to catch a wiring error. As I recall the mids didn’t work at all. I still have the detailed drawing I sent to JBL to show them how the mistake had been made.

    So my 4310s had minor ripples in the metal from the get-go.

    Now, in storage, they need new L-pads, and I am deathly afraid of thrashing these even more. Thanks a bunch for the heat gun and putty blade suggestion, and the re-gluing tips as well. I may now finally get up the courage to fix these speakers. This will save me big bucks in therapy.

    Now all I need is a good way to repair broken grill cloth frames (some 4310 owners will know just what I’m talking about).


    Izzy

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