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I've been asked to help repair a keyboard. On examining the keyboard I found the issues (circled) in the below image:

  1. A tear in the middle of the ribbon cable
  2. A tear across the end of the short side of the cable where it entered the PCB connector

Keyboard ribbon cable My original idea to repair this was to desolder the left side, buy a replacement ribbon cable, and then resolder and connect it. Unfortunately I've been unable to locate a replacement part.

My only other idea is to remove the insulation over the smaller tear and solder on small wires to bridge the tear. Then to remove the insulation on one side at the end and attempt to reinsert it into the PCB connector. Given the size of this cable I doubt my ability to solder the cables to rejoin them.

Does anyone else have any suggestions for an alternate method of repair?

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  • \$\begingroup\$ Probably your best bet is to keep searching. i needed something similar a while back and could not find it because it has name that was not obvious at the time. I can't for the life of me remember what it was. As long as the pitch and termination type matches and the length about the same you should be good. \$\endgroup\$
    – RoyC
    Feb 4, 2018 at 11:17
  • \$\begingroup\$ Thanks. That's what I suspected. I've searched with all references on the cable and not turned anything up but I'll continue to see if I can track a replacement down. \$\endgroup\$
    – Tom
    Feb 4, 2018 at 11:22
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    \$\begingroup\$ It's not a ribbon cable, it's a "flat flex". Personally I'd desolder it and the connector it fits into, throw them away and just re-make the connections myself with a load of thin gauge kynar wire. Probably would take half an hour with a decent iron. \$\endgroup\$
    – user98663
    Feb 4, 2018 at 11:38
  • \$\begingroup\$ Found it FFC or FPC. \$\endgroup\$
    – RoyC
    Feb 4, 2018 at 11:44
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    \$\begingroup\$ Thanks, the term "Flat Flex" has helped me find more suitable replacements. \$\endgroup\$
    – Tom
    Feb 4, 2018 at 19:48

3 Answers 3

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Removing the insulation in a reliable way might be very difficult. It may be impossible to have all ffc contacts work at the same time. Also, the cable will be shorter after this operation. Will the length be sufficient after mounting?

I'd try to get a ffc-cable with the pitch of the connector on the right and long enough to make all connections on the left. You have different options then.

One is, to cut the flat cable along its lenght on the left side, so that every trace has some cm for its own. You can then fold bend and trim the traces to meet the soldering points on the left PCB with minimized deviation and stress. Removing the insulation is neccessary, too. But you see, if it's sufficient when you try to solder it.

The other is to extend a complete FFC cable by soldering braided insulated wires to the left side. These are easy to connect to the left PCB.

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  • \$\begingroup\$ I've opted to buy a FFC with the same pitch which I'll insert into the PCB connector on the right. Then, as suggested, I'll cut & solder the other end to the PCB on the left. That feels much more achievable than removing the insulation from the existing cable. \$\endgroup\$
    – Tom
    Feb 4, 2018 at 19:50
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Had a similar situation recently. The steps I took were to put two layers of Kapton tap on the underside of the break to prevent further damage as I worked on it. I then exposed the copper each side of the break for about 3mm with the tip of a craft knife. I tinned this exposed copper (Kapron tape is heat resistant). used very fine tip iron 0.8mm and very fine wire - I joined the copper with strands of fine wire - strands inside light test leads work best. When soldered I then used heat glue to keep it rigid. Contemplated using Araldite but reckoned that if a connection subsequently lifted I would have difficulty - heat glue can be melted away and the connection can be reworked. Once I put the piece of equipment back in situ I was able to further re-enforce it accommodating its natural curve.

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I'm sure you managed to fix it by now, but if anyone else ends up in a similar situation this is what I did. I contacted Das Keyboard for a replacement and got one sent at no cost to me. They also offered an out of warranty repair for $45 if i was unable to do it myself.

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