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Thread: cap replacing in old networks

  1. #1

    cap replacing in old networks

    Hi all,

    is there any need for replacing caps in 40 years old passive crossovers like the LX 5 ? I know there are no electrolytic caps in these items but after 40 years...? BTW, any experience how to remove the tar-like filling in these crossovers ? What material is this filling ?

    Thank you in advance,


  2. #2
    Senior Member
    Join Date
    Aug 2003
    Santa Cruz, CA
    I've been doing this recently with excellent results. I'm not familiar with the LX-5s but have swapped the caps on a couple of sets of UREIs, JBL 4425s and, most recently, a set of KLH Model 5s. In all cases, they have all responded positively.

    My current rule of thumb is that most any speaker over +/-20 years is a candidate as a result.

    As for the crossovers potted in tar, I've been fortunate not to have to deal with those yet. I believe there have been posts here regarding how to rework crossovers like that. If it were me, however, I'd just build replacement crossovers and not have to deal with the sticky stuff.

    Hope that helps.



  3. #3
    Thank you,

    I have to replace either the wiring/ caps/ inductors because I buyed an old LX 5 which doesn´t work. Of course the pot is filled with the brown tar-like substance I must pull out so I can locate the damaged part. Any advice how to remove this filling...perhaps heating up works ? Any advice welcome.



  4. #4
    RIP 2011 Zilch's Avatar
    Join Date
    Jun 2004
    Berkeley, CA
    I have removed the "tar," which seemed to be more like a wax, actually, from one vintage crossover using a heat gun, which took nearly an hour to accomplish. Boiling water seems to be hot enough to melt it, also. I had concerns about potential toxicity of the material. Someone suggested it was "bee's wax." Not from any bee I ever knew, for sure.

    In the course of doing that, it occurred to me that the capacitors themselves, if they were of the sort used in other JBL crossovers, sealed with paraffein-like wax, would also be melted. Thus, the only point or purpose would be to recover tapped inductors or the case.

    Screw it. It'd have to be VERY valuable old crossover for me to mess with one anymore. They have to be rebuilt virtually from scratch, including hardware, switches, capacitors, resistors, terminals, coils, binding posts....

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