Repairing cables - ferrite bead and strain relievers

[tmcw]

Does anyone know how best to re-adhere ferrite beads and strain relievers to cables, like when repairing a games console controller that has had wires broken near where the cable emerges from the controller?

I found that the bead and reliever need to have a twist drill passed through to allow a fresh part of the cable to go through when the bad portion of cable was cut away. The material that came out was hard like the plastic cable cover, not like a silicone based material I half expected.

Does anyone know how it's done at the factory?

[llonen]

Re: Repairing cables - ferrite bead and strain relievers

Depends upon the strain relief, some of those are moulded to the cable itself, others are fed through and secured inside the unit. If its something that is likely to get some abuse then when I have these in for repair and mod will run a bead of silicon inside the strain relief. I get a lot of hoist controllers come through for rework from nursing and residential homes along with call bell systems. Call bell pendants I fill the 3/14" jack with either hot melt or silicone which works well enough.

[Unspun01]

Re: Repairing cables - ferrite bead and strain relievers

Internal wires are manufactured first. Then the internal wires are pulled through a jig that determines their orientation or lay. The foil shielding is applied over the wires at the same time. Then flexible protective cover over top.

Once cables are cut to pre-determined lengths, they may have ferrite beads placed over the cable prior to having connectors or terminations soldered or crimped onto the ends of the wires.

With cables now pre-manufactured, the cables are held in place in a mold where pressure injection of "stress relief material" is applied over the cover of the cable. You may notice that the cable material, and the injection molded material of the strain relief area are two different types of material. One melts much easier than the other, but they bond well together so they don't slip out.

Using a drill bit of appropriate diameter is very useful to "drill out" the conductor covering material from the stress-relief cone if you intend to re-use the stress relief cone.

Sometimes acetate glue (like crazy glue, etc) can be used, but is non-flexible. If it cracks, it may de-adhere from the cable and no longer provide the support you need.

I prefer to use a small dab of RTV silicone on the internal area where the cable and the stress cone meet to prevent it from pulling out under normal use. Once the RTV solicone cures, it is slightly pliable, and so long as it adheres to the cable cover inside the controller, the cable will not be allowed to pull out from the stress cone.

If you have sufficient cable length, you may also tie a knot in the cable inside the controller. This will absolutely prevent cable from pulling out (and no adhesives needed) but generally, there is little room to accommodate a know, and not usually good for the wires.

On one repair, after I pulled the cable through the stress relief cone, I inserted a toothpick between the wires (inside the cable cover) and this increased the effective diameter of the cable so it would not pull out from the stress relief cone.

Another time, I applied several wraps of vinyl electrical tape on the cable jacket adjacent to stress relief cone (inside controller). It worked for years until I sold it. But I was never rough with my stuff so while it worked for me, it may not work for everyone.

One other helpful bit of advice I can offer, is that sometimes it is tough to get the cable jacket to slide back through the stress relief cone upon re-assembly. Do not use oil because the cable will slip back out and defeat any use of adhesives. Instead, use a drop of Palmolive or other dish soap. This will reduce friction, and is easily wiped or washed away, and permits use of silicone or other adhesive.