potting compound removal

Discussion in 'Electronic Repair' started by Robert Morein, Jul 27, 2003.

  1. A small high frequency transformer in the monitor HV section of a Lecroy
    scope has failed.

    This part is difficult or impossible to obtain.

    It is potted inside a plastic box, which forms a tray. The underside, where
    the leads come out, is the potting compound, which has a crack down the
    center, perhaps due to the heat.

    I would like to de-pot this transformer to study the damage.

    I've heard that pineapple juice is the standard solution for removing
    potting compound.

    Any comments or suggestions?
     
    Robert Morein, Jul 27, 2003
    #1
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  2. Robert Morein

    Marko Guest

    "Robert Morein" <> wrote in message
    news:...
    > A small high frequency transformer in the monitor HV section of a Lecroy
    > scope has failed.
    >
    > This part is difficult or impossible to obtain.
    >
    > It is potted inside a plastic box, which forms a tray. The underside,

    where
    > the leads come out, is the potting compound, which has a crack down the
    > center, perhaps due to the heat.
    >
    > I would like to de-pot this transformer to study the damage.
    >
    > I've heard that pineapple juice is the standard solution for removing
    > potting compound.
    >
    > Any comments or suggestions?


    Robert, I was told that if the unit is old enough that it may dissolve in
    solvent. Try varsol or mineral spirits, they probably won't dissolve the
    enamel on the wires. As I understand it, in the 30s 40s and possibly into
    the 50s and 60s they used coal tar or something like that.

    In later years I think they started using some rubbery type stuff.

    Faster thinners like MEK or xylene will probably dissolve it , but they
    might also dissolve the enamel, and also your nervous system.

    Never heard about pineapple juice. If it is the acidity then vinegar may
    also work.

    If you figure it out, please post your results. Mark


    >
    >
     
    Marko, Jul 27, 2003
    #2
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  3. "Marko" <> wrote in message
    news:...
    >
    > "Robert Morein" <> wrote in message
    > news:...
    > > A small high frequency transformer in the monitor HV section of a Lecroy
    > > scope has failed.
    > >
    > > This part is difficult or impossible to obtain.
    > >
    > > It is potted inside a plastic box, which forms a tray. The underside,

    > where
    > > the leads come out, is the potting compound, which has a crack down the
    > > center, perhaps due to the heat.
    > >
    > > I would like to de-pot this transformer to study the damage.
    > >
    > > I've heard that pineapple juice is the standard solution for removing
    > > potting compound.
    > >
    > > Any comments or suggestions?

    >
    > Robert, I was told that if the unit is old enough that it may dissolve in
    > solvent. Try varsol or mineral spirits, they probably won't dissolve the
    > enamel on the wires. As I understand it, in the 30s 40s and possibly into
    > the 50s and 60s they used coal tar or something like that.
    >
    > In later years I think they started using some rubbery type stuff.
    >
    > Faster thinners like MEK or xylene will probably dissolve it , but they
    > might also dissolve the enamel, and also your nervous system.
    >
    > Never heard about pineapple juice. If it is the acidity then vinegar may
    > also work.
    >
    > If you figure it out, please post your results. Mark


    This part was made 1989. It's from a digital scope :).
    The potting material is hard and shiny, possibly a form of two component
    acrylic.
     
    Robert Morein, Jul 27, 2003
    #3
  4. Robert Morein

    Jim Adney Guest

    On Sat, 26 Jul 2003 21:21:06 -0400 "Robert Morein"
    <> wrote:

    >A small high frequency transformer in the monitor HV section of a Lecroy
    >scope has failed.


    >It is potted inside a plastic box, which forms a tray. The underside, where
    >the leads come out, is the potting compound, which has a crack down the
    >center, perhaps due to the heat.
    >
    >I would like to de-pot this transformer to study the damage.


    If the potting is soft you may just be able to dig it out. If you have
    the hard stuff, then you could try various solvents to see if any of
    them would soften it. I've had some luck with acetone, but I had to
    leave it soaking overnight, dig out the softened portion and then
    repeat. This can take many days, but is workable if you have the time.

    >I've heard that pineapple juice is the standard solution for removing
    >potting compound.


    I've never heard of this and it doesn't sound reasonable to me. The
    only thing in the juice would be a mild acid which shouldn't do
    anything to the potting compound, but it might eventually damage metal
    parts that were in there.

    -
    -----------------------------------------------
    Jim Adney
    Madison, WI 53711 USA
    -----------------------------------------------
     
    Jim Adney, Jul 27, 2003
    #4
  5. "Robert Morein" <> wrote in message
    news:...
    >
    > This part was made 1989. It's from a digital scope :).
    > The potting material is hard and shiny, possibly a form of two component
    > acrylic.
    >



    Try De-Solv-It which you can find at better hardware stores or Eposolve,
    which is very dangerous and available from industrial suppliers such as
    McMaster-Carr.
     
    Peter Gottlieb, Jul 27, 2003
    #5
  6. Robert Morein

    James Sweet Guest


    >
    > This part was made 1989. It's from a digital scope :).
    > The potting material is hard and shiny, possibly a form of two component
    > acrylic.
    >
    >


    That's epoxy, good luck dissolving it, anything that will remove it will
    likely destroy anything inside it.
     
    James Sweet, Jul 27, 2003
    #6
  7. Robert Morein

    Nigel Cook Guest

    "Robert Morein" <> wrote in message
    news:...
    > A small high frequency transformer in the monitor HV section of a Lecroy
    > scope has failed.
    >
    > This part is difficult or impossible to obtain.
    >
    > It is potted inside a plastic box, which forms a tray. The underside,

    where
    > the leads come out, is the potting compound, which has a crack down the
    > center, perhaps due to the heat.
    >
    > I would like to de-pot this transformer to study the damage.
    >
    > I've heard that pineapple juice is the standard solution for removing
    > potting compound.
    >
    > Any comments or suggestions?
    >
    >


    In a similar circumstance faced with black ,hard, probably
    epoxy potting I used a ball mill in a dremmel. Like a rotary
    burr but instead of a cylinder on a mandrel it is a small sphere
    of burr/file form a few mm in diameter. Cutting
    in section by section ,then breaking each section away.
    Leaving the external pinning area to last.,counted turns off
    and other features (wiring sense,interlayer paper etc)and rewound.
    Before starting to break apart make a plan of the
    pinning and do a grid plot of all combinations of inter-pin DC resistance
    and AC inductance measurements as you are
    bound to cut some wires in the process. Mark any cut ends
    with indelible felt tip pen marks - good luck.
    Time consuming but as
    the replacement cost I was quoted was a totally
    ridiculous 700 GBP ( 1000 dollars ) for a potted
    box less than 2 inch cube ,well worth trying

    e-mail (removing .....) .u.....k
    electronic hints and repair briefs , schematics/manuals list on
    http://homepages.tcp.co.uk/~diverse

    Nigel,Diverse Devices,Southampton,England
     
    Nigel Cook, Jul 28, 2003
    #7
  8. Robert Morein

    Len Guest

    Back in the says of videocypher 2 sat board hacking they used to use a
    heat gun with a concentrator on it, heat up a small spot and use a small
    screwdriver to dig it out. Its a real bitch to do but I have seen
    people totally remove the stuff and leave all the traces and parts
    intact.

    On Sun, 27 Jul 2003 17:34:42 GMT, "James Sweet" <>
    wrote:

    >
    >>
    >> This part was made 1989. It's from a digital scope :).
    >> The potting material is hard and shiny, possibly a form of two component
    >> acrylic.
    >>
    >>

    >
    >That's epoxy, good luck dissolving it, anything that will remove it will
    >likely destroy anything inside it.
    >


    REMOVE the NOCRAP in my address to reply.
     
    Len, Jul 28, 2003
    #8
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