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stripping "ribbon cable?" ??

Discussion in 'Electronic Repair' started by Sean, May 16, 2005.

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  1. Sean

    Sean Guest

    Hi,
    I had to open my projector to fix a problem with it and I notice a break in
    one of the "ribbon cables" coming from one of the LCD panels..

    This cable is completely flat and has "gold fingers" at the end of it (not
    the traditional wire that i'm used to dealing with) .. I can see through the
    insulation a break in a couple of the tracks so I need to trim the cable
    back..

    Question is, how do you remove the insulation on the end of one of these
    cables!?!? .. I really need to get this right the first time coz there's not
    much further back that I can trim it..

    Any info would be greatly appreciated (note if replying by email remove the
    NOSPAM)

    Thanks,

    Sean
     
  2. NSM

    NSM Guest

    I'd be inclined to try to patch the cable. Sometimes the ends are special,
    not just stripped cable.
     
  3. "ribbon cables"...

    Usually these cables are replaced, not repaired.
    If you can get a new part from the manufacturer you'd be much better off
    than trying to repair it. It's nearly impossible and not worth the effort.
     
  4. CJT

    CJT Guest

    Usually ribbon cable is used with insulation displacement connectors,
    so isn't stripped.
     
  5. Rick

    Rick Guest

    Are you sure these breaks are causing a problem? If it ain't
    broke, etc.

    You'd almost certainly be better off patching the tracks with
    some conductive paint, rather than try and reattach the entire
    cable.
     
  6. Sean

    Sean Guest

    I thought the same thing, but I can't see how conductive paint can be used
    when the whole thing is insulated.. it's basically flexible PCB.. I have
    ended up cutting it back but that doesn't help because now I've lost the
    gold connectors..
    I'm guessing there's no way to fix the cable now!?

    If not, can this sort of cable be bought.. is it standard!?

    Thanks,

    Sean
     
  7. can this sort of cable be bought.. is it standard!?
    If you can get in touch with the manufacturer's parts department maybe
    you could order it. It's probably not available anywhere else.
     
  8. Ian Malcolm

    Ian Malcolm Guest

    If its water clear plastic the method below WILL NOT WORK
    (plated/conductive ink tracks and low melting point plastic), but at
    this point you have nothing to loose so try it anyway. It also works
    for the white ribbbon cables with the pretinned conductors but skip the
    tinning step below (a *brief* touch with an iron can help you scrape off
    the last of the white plastic but always risks lifting a track)

    If its all a sort of golden yellow colour, the cable is almost certainly
    a Kapton substate flexible PCB with an additional layer laminated on top.

    AS LONG AS THE TRACK SPACING AND ORDER IS IDENTICAL AT THE BREAK AND THE
    END ITS FIXABLE.

    Take an *ADJUSTABLE* Dremel tool (actually the really cheap clone ones
    with the external powerbrick works fine for this sort of stuff, fit a
    small ball ended DIAMOND burr and turn the speed down pretty slow. Take
    a fine tipped pen (e.g. CD marker) and mark off the length you need to
    strip. Grind off the top layer from each contact one at a time. Keep
    the burr moving around all the time or you will go right through. When
    you see a spot of bare copper, work around it, dont go back over it
    because its VERY thin. Its best to work against a slightly resiliant
    backing such as a block of expanded polystyrene or a pencil erasor.

    Finally finish by fluxing the contacts with a flux pen or some liquid
    rosin flux and tinning all the contacts (very little solder, fine tipped
    iron and *very* brief contact. Any small remaining sport of Kapton can
    be cleaned off the tinned surface using a small jewlers screwdriver with
    the end ground at an angle as a knife blade, edge at 45 deg. to shaft
    and about a 30 deg included angle at the actual cutting edge. Sharpen
    on a fine india stone or 600 grit wet & dry paper using some light oil.
    (usefull general purpose tool when patching fine pcbs) Scrape very
    gently. Clean up excess tinning with fine desoldering braid ( braid
    touching the tip, then briefly wipe the contact with the braid still
    touching the tip) Trim back to fresh braid for every contact. If
    you've done it right none of the tracks have lifted. I've had some
    success sticking one or two back down with a tiny drop of superglue
    applied with a toothpick and hold the track down gently for five minutes
    with a very small screwdriver or the point of the scraper mentioned above.

    Finally, if there is a backing strip on the original connector, strip it
    off carefully using a thin sharp knife to worry at the glue line (or
    even the above scraper again). Remove any residual glue with some
    solvent and a cotton bud. Roughen the surface with the diamond bur on
    really slow and do the same to the back side of the ribbon cable Stick
    in place with a tiny drop of suitable glue (I dont like superglue for
    this, it doesnt stand up to being flexed and it tends to get on the
    track side and rip tracks off when you take the clamp off) Clamp flat
    till fully dry. Clean the tinned contacts with isopropyl alcohol or
    methylated spirits and a cotton bud. Apply the lightest smear of a good
    contact cleaner/lubricant (to slow down the inevitable tarnishing) and
    insert into matching socket and pray to Deity of Your Preference :)


    I STRONGLY reccomend practicing on the scrap end you cut off. DONT
    strip the wrong side of the cable (LOOK AT THE SOCKET CONTACTS!). I did
    a £1000 proffesional video head last week and it took me about an hour
    for about 20 contacts. (now that was really fiddly, grinding cables 1"
    away from a really delicate head drum and having to keep both head
    cables (both damaged) the same length to maintain rotational balance) :)
     
  9. Ian Malcolm

    Ian Malcolm Guest

    If its a streight cable with both ends the same and detachable, take it
    down a good video repair shop and see if they can match it. So long as
    the contact pitch is correct you can always cut down a wider cable.
     
  10. geo73

    geo73 Guest

    I think this kind of ribbon goes with the lcd...
    If you manage to order the kit will you be able to
    adjust the lcd to the rest of the prism??
     
  11. Sean

    Sean Guest

    Thanks so much for the info.. I'll have to look into whether I'm up for it..
    I really wish near where I lived there was someone I could pay to do this..
    I mean since the projector is worth over $2500 it'd be worth paying upto
    about $1000 to get someone to do this.. pretty good for an hours work! :)

    I just need some of the equipment

    --
    Sean

     
  12. nolsar

    nolsar Guest

    Take it to a repair joint anywhere, probly $50 an hour.

     
  13. Asimov

    Asimov Guest

    "Sean" bravely wrote to "All" (16 May 05 12:24:01)
    --- on the heady topic of "Re: stripping "ribbon cable?" ??"

    Se> I thought the same thing, but I can't see how conductive paint can be
    Se> used when the whole thing is insulated.. it's basically flexible PCB..
    Se> I have ended up cutting it back but that doesn't help because now I've
    Se> lost the gold connectors..
    Se> I'm guessing there's no way to fix the cable now!?

    Se> If not, can this sort of cable be bought.. is it standard!?

    Remove the sockets and solder in some ordinary wire ribbon cable or
    jumper wires if you have the patience. Had to do that with early rca
    vcr's that had crummy spring type sockets.

    A*s*i*m*o*v

    .... Digital circuits are made from analog parts.
     
  14. Jim Adney

    Jim Adney Guest

    Would it be possible to just run a single conductor wire in parallel
    with the single broken conductor, and leave the rest of the ribbon
    undisturbed? The single wire might not need to be soldered right at
    the end of the ribbon either. If it is carrying low frequency info it
    could be connected to any nearby point that is connected to the
    conductor you're trying to fix.

    -
     
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