EB5AGV's Workbench: Flat cable repair

They said it was impossible... so I did it!

AGVradio Lab

Since more than 20 years ago, I fix amateur radio gear. It all started with a CB rig and, some decades later, it is my main work. During these years I have fixed more than a thousand rigs, but I had never attempted to do what I describe on this page. As it was successful, I want to share it with all of you. I hope it may be useful to somebody else!


Cable as found

This is what I found on the rig (an Icom IC-910H) I was about to fix (or at least try to fix!). It was pretty discouraging:

I got out the flat cable, to find it was completely ruined. And, what is even worse, someone had bent it and tried to use it that way... I wonder how the rig didn't end up on flames!

So there I was... Getting that part from the rig manufacturer meant waiting for weeks... and I wanted to fix the rig or, at least, find other problems. So, well, could that cable mess be fixed?. I had never tried that so it was a very good moment to do it, right ;-)?

Repairing the cable

First, I studied the flat cable: it is made of conducting flat traces embedded on a flexible strip. Then, on its tips, there is a missing cover layer and, on the other side, a flexible plastic which is glued to the cable so it can be plugged.

So first point was to cut the damaged part (but just the minimum length, as the resulting cable would be shorter) and remove the isolating layer. Cutting the damaged cable was easy. Removing the layer was not!. I did a very tiny cut with the cutter and a ruler, just feeling when I was reaching the embedded metal conductors, in order to not damage them:

As you can see in the picture, the outer plastic layer is partially removed, showing a white layer which covers the contacts. Once the plastic cover is removed (this is not easy and patience pays), I needed to remove the white layer. I tried to dissolve it with alcohol but that didn't work, so I removed it carefully using an small flat screwdriver. Please, note that the traces are delicate and you need to maintain them as flat as possible and of course bounded to the flexible layer.

This is the result on two traces:

As it looked OK, I did the rest of one side:

And then the other side:

OK, now there is another thing to consider: these cables have a plastic piece on their extremes, to strengthen them so they can be plugged into the connectors. I needed to add the same ending to my refurbished cable. I measured a good cable and it was 0.3mm thick. The cable I had worked on, at its extremes, was now just 0.1mm thick. So I needed to add an extra 0.2mm. I looked around my lab and found some color filters which, yes, where exactly 0.2mm thick!

I cut the exact size (it is important to keep the width exactly as it is on the original cable) and glued with epoxy to the flat cable:

Fixed cable

After the epoxy cured, I cut just a tiny fraction of the cable tip, as there was some small gobs of glue on it which could prevent a correct connector insertion.

This is the finished cable:

And, yes, the rig works fine with the new cable!

So, never say it is impossible :-)!